Abstract Threshold signature, as a privacy-preserving distributed signature, has become the underlying technology in various fields over the last decade. It is useful to protect against a single point of failure and can effectively ensure key security. In recent years, many different digital signatures have been thresholded and many new techniques, algorithms, and protocols have been proposed. This paper introduces the mainstream threshold signature schemes based on the signatures by several standards. We comprehensively investigate various aspects of these threshold signature schemes for comparison and evaluation, and provide the relevant applications and more potential directions for threshold signature.

The most efficient asynchronous Byzantine fault tolerant (BFT) framework innagreement settings is due to Ben-Or, Kemler, and Rabin (BKR), wherenis the total number of replicas. Despite recent efforts to bring BKR closer to practical deployment, state-of-the-art designs are still hampered by the inherent mutual waiting between the broadcast and agreement phases. In response, we propose ByzTopia, a new asynchronous BFT protocol that removes this performance bottleneck. Its technical core is to decouple these two phases without introducing additional cryptographic primitives. To enable a more efficient decoupling of the broadcast and agreement phases, we introduce multi-shot reliable broadcast (MRBC), which ensures that replicas deliver messages in a well-ordered sequence across consecutive slots. We implement ByzTopia and evaluate it in various settings. Experimental results show that ByzTopia achieves up to 6.54× the throughput of PACE (for n == 31), the state-of-the-art asynchronous BFT of the same type, and 2.65× that of FIN (for n = 16), the state-of-the-art signature-free asynchronous BFT.

By introducing collision information, the existing side-channel Correlation-Enhanced Collision Attacks (CECAs) performed collision-chain detection, quickly filtered out candidates unsatisfying collision conditions and extracted a part of optimal candidates for further process, thereby rapidly and significantly reducing the key candidate space and the difficulty of key recovery. However, they are still limited by disadvantages such as serial implementation, complex parameter settings and lack of intelligence, resulting in a low success rate of key recovery. To address these issues, we first present a Collision Detection framework with Genetic Algorithm (CDGA), which exploits Genetic Algorithm to detect the collision chains and has a strong capability of global searching. Secondly, we theoretically analyze the performance of CECA, and bound the searching depth of its output candidate vectors with a confidence level using a data-driven hypothesis test that provides confidence bounds for Gaussian leakages and an approximation based on Central Limit Theory (CLT)for non-Gaussian cases, which facilitates effective and stable population initialization. Thirdly, benefiting from our hypothesis-test-guided design, we propose a goal-directed mutation that prioritizes promising collision candidates, thus improving efficiency and adaptability of the CDGA. Finally, to optimize the evolution of CDGA, we introduce a roulette selection strategy to employ a probability assignment based on individual fitness values to guarantee the preferential selection of superior genes. Comprehensive experiments on DPA Contest v4.1 (AES-256 with Rotated S-boxes Masking) and an AT89S52 AES-128 platform demonstrate that CDGA achieves faster convergence and higher key-recovery success rates compared with TOC/FTC/FCC and Wiemers’ cumulative-correlation selection.

Attribute revocation is a secure data-sharing system that allows user revocation of shared data. The most effective attribute revocation scheme is still less effective in the revocation process. When revoking a user's access rights to a specified ciphertext, both that ciphertext and the keys of all other users must be updated. Similarly, when revoking a user from accessing all ciphertexts, all ciphertexts related to the revoked user and the keys of all non-revoked users must be updated, with computational cost linear to the number of attributes associated with the revoked user. In this work, to enhance the effectiveness of revocation, we design a cloud data-sharing system that supports flexible revocation. By introducing edge-server-assisted key puncturing techniques, our approach eliminates the need to update ciphertext and other users' keys when revoking a user's access rights to a specific ciphertext. Additionally, we leverage key splitting technology to divide data users' permissions between the data owner and the authority, ensuring that the update overhead for non-revoked users remains constant when revoking a user's access to all ciphertexts. On resource-constrained devices, when involving 50 attributes, non-revoked users only need approximately 0.02 milliseconds to update their keys, resulting in a 25x improvement in update speed.

Digital and physical identity authentications are often implemented concurrently to meet strict access control for online services. Although privacy-preserving digital credentials provide strong guarantees such as anonymity and minimal disclosure, these benefits are compromised if holders must simultaneously present physical identification (e.g., government issued IDs) to establish ownership. To securely bind digital credentials to their physical holders while preserving privacy, a new protocol called card-based anonymous credentials (cbAC) was proposed by Hesse et al. (USENIX Security'23). However, this approach faces two significant drawbacks: the size of the communication during credential presentation scales linearly with the number of disclosed attributes, and it lacks revocability, which is essential for internal governance, including identity management and accountability. In this paper, we bridge the above gap by first introducing a constant-size two-party proof of knowledge protocol in asymmetry settings, where there exists a disparity in storage and computational resources between the two parties. Furthermore, building upon this two-party proof of knowledge protocol and utilizing signatures with randomizable keys, we meticulously design a cbAC scheme that is both efficient and capable of supporting revocation. We formalize all notions and conduct a rigorous security proof of the proposed construction. Finally, we present benchmarks from our implementation to illustrate the better than-state-of-the-art performance and features of our solutions.

The widespread deployment of smart grids has brought significant convenience to residential life. However, it also presents key challenges for data aggregation in smart grids.M1: The hierarchical structure of smart grid consumers (e.g., residential, industrial, commercial) requires differentiated allocation strategies to meet varying electricity demands while protecting consumer privacy.M2: The existing methods, such as superincreasing sequence, often face efficiency challenges, particularly when dealing with multidimensional data.M3: Smart meters continuously collect diverse power consumption data containing users' private information, which is vulnerable to tampering or loss, compromising data integrity and impacting power dispatch decisions. To address these challenges, this paper proposes a blockchain-based, efficient, verifiable, and weighted multidimensional data aggregation scheme for smart grids. First, a novel five-layer cloud-chain-assisted multiscenario data security aggregation model is proposed. Second, instead of using superincreasing sequences, we introduce the Chinese Remainder Theorem to process multidimensional data, thereby reducing communication complexity. Additionally, the property of quadratic reciprocity is leveraged to enhance the decryption method of the Paillier cryptosystem, reducing computational overhead. A weighted aggregation function is implemented to accurately aggregate data based on different user attributes. Furthermore, we propose two sample configurations to address distinct scenario requirements. Security analysis and experimental results demonstrate that the proposed scheme meets practical requirements in terms of both security and efficiency.

As modern communication technologies advance, the Industrial Internet of Things (IIoT) is progressively evolving towards greater intelligence. The extensive implementation of smart grids has significantly affected IIoT factories. Data aggregation is commonly used to protect the factory's privacy. However, existing multi-dimensional data aggregation schemes lack flexibility and are vulnerable to internal attacks, where private data from certain smart devices may be decrypted by insiders. Moreover, replacing related devices necessitates updating the keys of the entire system, which incurs heavy overhead. To address these issues, a multi-dimensional privacy-preserving data aggregation scheme based on homomorphic proxy re-encryption (MPDA-HPR) is proposed. Using a modified Paillier encryption algorithm supported by proxy re-encryption and super-increasing sequences, the proposed scheme enhances flexibility and scalability. Security analyses demonstrate that the proposed scheme can withstand various security threats and effectively preserve the privacy of devices. Finally, the prototype is implemented and evaluated, demonstrating that the proposed scheme is robust, efficient, and feature-rich.

Web3 has attracted considerable attention in fields including DeFi, DApps, and NFTs due to its decentralization, enhanced privacy, and user-centricity. However, interoperability and scalability challenges hinder its widespread adoption. While deploying anonymous credentials across Web3 networks to enable cross-network service access is a potential solution to these challenges, existing credential systems remain limited by centralized management, high energy consumption, and credential abuse, making them unsuitable for Web3 environments. To overcome these limitations, we propose a decentralized anonymous functional credential (DAFC) scheme that is efficient, privacy-preserving, and linkable. Unlike existing schemes, DAFC enables users to generate a single proof embedding attributes$x$for requesting services under different access policies. Each provider can use the functional key$sk_{F}$associated with their respective access policy$F$to extract$F(x)$for attribute verification. This significantly reduces authentication computational overhead. Furthermore, DAFC's linkability effectively mitigates credential abuse risks. As an additional contribution, we propose a novel construction of non-interactive zero-knowledge functional proof (fNIZK) based on one-out-of-many proofs and functional encryption for inner products, which is the building block of DAFC. Security analysis demonstrates that DAFC achieves anonymity, unforgeability, and linkability. Performance evaluation shows that DAFC outperforms prior schemes in both computational and communication overhead when requesting at least 6 services with distinct access policies.

In recent years, deep learning side-channel analysis (DLSCA) has garnered significant attention, with the choice of model architecture greatly influencing attack efficiency. Currently, convolutional neural networks (CNNs) have become the dominant architecture in the field of side-channel analysis (SCA), and multi-scale CNNs (MCNNs) have gained favor among certain researchers due to their ability to capture information across various scales. However, effectively obtaining multi-scale information from datasets requires the customization of appropriate hyperparameters for each channel, and the hyperparameter tuning process is often time-consuming and labor-intensive. This presents a technical barrier for non-experts or those seeking to simplify their workflow. Such limitations lead researchers to overly rely on fixed hyperparameter models based on specific datasets, overlooking the differences between various data samples, which in turn affects the model’s reusability and generalization capability in broader scenarios. To address these issues, we propose an adaptive MCNN framework based on automated machine learning, named Auto-MCNN. We evaluated the effectiveness of this framework on multiple private and public datasets. To further investigate the variations in the network’s feature extraction capabilities, we employed an improved heatmap visualization method to illustrate the network’s areas of focus. Experimental results demonstrate that the optimized Auto-MCNN model can be more widely applied to the analysis of side-channel leakage traces, significantly enhancing overall analysis efficiency.

The proliferation of data-driven services on cloud platforms, coupled with stringent regulatory frameworks like the General Data Protection Regulation (GDPR), necessitates crypto-graphic solutions that ensure secure and efficient data exchange. However, simultaneously achieving post-quantum security, bilateral access control, data authenticity, simplified key management and efficiency remains a critical challenge. To address these issues, this paper introduces a certificateless lattice-based matchmaking encryption (CLLME) to provide post-quantum security while obviating key escrow and certificate management. The proposed scheme enforces bilateral access control, allowing both data senders and receivers to specify matching access structures; decryption is thus contingent upon mutual authorization. Moreover, to prevent the costly decryption of numerous irrelevant ciphertexts, CLLME embeds a lightweight authenticity operation, which enables retrieval of useful data, effectively creating a high-performance filter for encrypted data streams. We formally prove that CLLME achieves indistinguishability against chosen-plaintext attacks and existential unforgeability against chosen-message attacks under lattice-based assumptions. Experimental evaluations demonstrate that CLLME maintains favorable communicational and computational efficiency, confirming its suitability for practical and scalable deployment in regulation-compliant, large-scale data sharing environments.

Anonymous credentials offer privacy-preserving authentication and authorization by making assertions about identity in the digital realm. To overcome the reliance on a single trusted issuer, decentralized variants have emerged. A classic approach is to split the responsibility of issuing credentials among multiple issuers in a threshold manner (e.g.,t-out-of-n). Unfortunately, among existing threshold protocols, non-interactive practical constructions can only guarantee security in honest majority settings, while interactive constructions face two primary efficiency bottlenecks: either they require an excessive number of interaction rounds, or they fail to support constant-size credential showings for selective disclosure. In this work, we address these challenges by presenting a threshold issuance anonymous credential (TIAC) protocol, built upon the recent advanced signatures, i.e., Equivalence Class Signatures (EQS). Our proposed solution involves a three-round protocol that realizes a standard threshold issuing functionality, providing composable security against a malicious adversary corrupting the majority of issuers. We thereafter introduce a provably secure construction of the TIAC protocol with constant-size showings by combining the proposed threshold issuing protocol and set commitments. We rigorously prove our protocol in the universal composability (UC) framework. The practicality of our protocol is demonstrated through benchmark comparisons with the state-of-the-art EQS-based solution (ASIACRYPT ’24). The benchmarking results show that, with 64 participating issuers, our improvements go up to 6.72× for the threshold issuance phase when observed over WAN.

Privacy-preserving blockchain systems are essential for protecting transaction data, yet they must also provide auditability that enables auditors to recover participant identities and transaction amounts when warranted. Existing designs often compromise the independence of auditing and transactions, introducing extra interactions that undermine usability and scalability. Moreover, many auditable solutions depend on auditors serving as validators or recording nodes, which introduces risks to both data security and system reliability. To overcome these challenges, we propose SilentLedger, a privacy-preserving transaction system with auditing and complete non-interactivity. To support public verification of authorization, we introduce a renewable anonymous certificate scheme with formal semantics and a rigorous security model. SilentLedger further employs traceable transaction mechanisms constructed from established cryptographic primitives, enabling users to transact without interaction while allowing auditors to audit solely from on-chain data. We formally prove security properties including authenticity, anonymity, confidentiality, and soundness, provide a concrete instantiation, and evaluate performance under a standard 2-2 transaction model. Our implementation and benchmarks demonstrate that SilentLedger achieves superior performance compared with state-of-the-art solutions.

Anonymous tokens (AT) have emerged as a critical tool for privacy-preserving authentication. However, state-of-the-art systems face two principal technical limitations: the risk of token transferability, which compromises accountability, and reliance on centralized issuers, which introduces a single point of failure. To address these limitations, we present the first construction of a non-transferable anonymous token system with decentralized issuance (D-NTAT). In particular, our construction supports a dynamic set of issuers, empowering users to obtain tokens by interacting with any subset of the current issuers. The token is publicly verifiable, unlinkable to the issuance process, and, most importantly, non-transferable, even though it is redeemed anonymously. To accomplish this objective, we formalize the notions of D-NTAT, provide a specific construction of a set of protocols from which variants offering enhanced functionalities can be derived, and rigorously prove their security properties. Finally, a proof-of-concept implementation is presented to evaluate their efficiency, which is crucial for blockchain applications such as electronic voting.

Secure multiparty computation (MPC) over Z2kis more efficient than computations over fields, and studying MPC protocols under malicious security has practical application value. Malicious security with a dishonest majority over rings remains challenging. The most popular approach is SPDZ2k, however, this is a specific protocol that does not support the transformation of any existing semi-honest MPC protocols into malicious security protocols. The zero knowledge proof (ZKP)-based compiler satisfies this requirement. Existing state-of-the-art protocols have logarithmic online communication overhead in terms of the circuit size |C|, and their direct application to rings is nontrivial as they were originally designed for finite fields. In this work, we investigate the communication overhead to develop malicious security protocols. We bridge the gap between malicious security with abort and semi-honest security, by constructing a “GMW-style” verification protocol to achieve malicious security in a dishonest majority setting. This approach incurs a constant online communication overhead by enhancing the machinery of zero-knowledge fully linear interactive oracle proof (zk-FLIOP). Additionally, we extend the zk-FLIOP to work over any ring by invoking reverse multiplication friendly embeddings (RMFEs). Our results show that the online communication complexity of the verification process depends on only the security parameter, the number of parties, and the ring size. Furthermore, for small-scale circuits over Z2, we designed a distributed lookup table argument where both the total communication complexity and the computational cost are independent of the circuit size but of the input wires.

In vehicular ad-hoc networks (VANETs), message reporting is an effective method for improving traffic safety and efficiency. Most existing VANET message reporting schemes rely on the trust value of a single vehicle to determine message authenticity, which leads to unreliable message sources. Even multi vehicle-assisted reporting schemes are limited by the assumption that all vehicles have the same credibility, which does not reflect the actual dynamic VANET environment in which vehicles have different credibilities. To address this issue, we propose a blockchain-assisted VANET message reporting scheme with weighted threshold signatures. Through the design of weights, the credibility of different vehicles is quantified, and the impact of vehicles on the signing process is differentiated. Threshold signature generation relies on the weight sum of all signatories reaching a predetermined threshold, to enable flexible and reliable message reporting. Security analysis shows that our proposed scheme combined with blockchain can satisfy the security and privacy requirements of VANET message reporting. Performance analysis indicates that our proposed scheme outperforms the most advanced VANET message reporting schemes in terms of transmission and computation performance.

With increasingly complex tasks, cooperation among multiple unmanned aerial vehicle (UAV) groups has become more significant. However, in complex operational environments, UAVs may operate outside the communication coverage of the trusted authority (TA), making continuous online TA services unavailable. Under such circumstances, most existing group management methods have difficulty achieving group fusion and cannot flexibly update post-fusion member certificates. Therefore, we propose an autonomous UAV group management scheme based on mobile proactive secret sharing. First, the scheme achieves autonomous group fusion by updating the subsecrets of UAVs. Second, without the participation of a TA, the scheme supports the dynamic self-updating of certificates, ensuring secure communication in the new group and continuous availability of certificates. Security proofs and analyses show that the proposed scheme is secure under the random oracle model and can resist several common attacks. The experimental results demonstrate that the proposed scheme outperforms related schemes in computational performance and is suitable for secure and efficient UAV group management scenarios.

As Flying Ad-hoc Network (FANET) evolves toward larger scales and higher levels of autonomy, the importance of secure and efficient group communication continues to grow. However, resource-constrained unmanned aerial vehicles (UAVs) face dual challenges: limited computational power struggles to meet the high demands of complex cryptographic algorithms, while bandwidth constraints exacerbate communication overhead caused by multi-round interaction mechanisms. Moreover, existing solutions find it hard to support dynamic group environments and are prone to single point of failure (SPoF) in centralized architectures, which significantly compromises system reliability and scalability. To address these issues, this paper proposes a novel key agreement protocol for FANET. The protocol employs an improved tree-based key encapsulation mechanism (iTreeKEM) to support rapid key updates in highly dynamic environments. It reduces the computational cost for each group member by 90.08% even when the group size reaches 128. To further enhance system robustness, the protocol introduces a smart contract-based distributed leader election mechanism, effectively eliminating SPoF. The security of the proposed protocol is guaranteed by the CDH problem under the generalized selective decryption (GSD) model. Finally, we implement the protocol in NS-3 simulations, and the results demonstrate its effective applicability to FANET.

Clustering algorithms, as the core technology in data analysis, can extract potential patterns and regularities from complex data. However, deploying k -means clustering on resource-limited devices remains a challenge. Despite the promise of cloud computing, outsourcing data to a remote cloud leads to high latency and privacy risks. Moreover, the stability and speed of cloud can be affected by the state of network and configuration, which leads to computation error. Therefore, we design a secure and dropout-resilient k -means clustering scheme based on cloud-edge-client collaboration architecture. In our scheme, cloud server simply generates multiplication triples in pre-processing phase and can be offline. In online phase, IoT devices secretly share the raw sensing data with three edge servers. Then edge servers accomplish the clustering task interactively. We propose four basic protocols based on vector space secret sharing, including Euclidean distance, comparison, minimum and division protocols. By applying these protocols, we construct a clustering scheme that can tolerate the exit of one edge server and corruption of two edge servers. Since edge servers are generally located in trusted environment, we allow them to reconstruct clustering result and provide low-latency and high-reliability service. We prove that the basic protocols and clustering scheme are secure against semi-honest adversary. We conduct the experiments on two realistic datasets, showing that our scheme has good efficiency and is suitable for practical application.

Federated Learning (FL) has been widely applied across various domains for collaborative training while preserving data privacy, but it remains highly vulnerable to poisoning attacks that compromise the global model’s integrity and performance. Existing clustering-based defense methods, such as FLAME, filter out malicious models by calculating vector similarities between local models but rely heavily on the assumption of independent and identically distributed client data. In this paper, we propose KSFed, a novel defense framework that detects poisoning attacks through the analysis of probability distributions of model parameters. KSFed treats model parameters as samples from a distribution, where benign models exhibit similar patterns while malicious models show significant deviations, allowing it to identify and filter out malicious models without relying on assumptions about attack types, adversarial strategies, or client data distributions. Experimental results show that KSFed surpasses FLAME and other clustering-based defenses, reducing backdoor accuracy (BA) by 8.33% to 99.74% under sophisticated attack strategies and highly non-IID client data distributions, while maintaining the global model’s main task accuracy (MA).

The Internet of Medical Things (IoMT) has achieved remote diagnosis and real-time health monitoring through intelligent sensor devices and Internet of Things (IoT) technology, providing great convenience for analyzing medical conditions between doctors and patients. However, sensitive information such as patient medical data may face security challenges such as data leakage and abuse during transmission in the IoMT. To ensure the confidentiality and unforgeability of medical data transmission, scholars have proposed many cryptographic schemes. With the development of quantum computers, schemes based on traditional cryptographic primitives have become insecure. Existing cryptographic schemes for IoMT cannot simultaneously meet the security requirements of high communication performance, low computational overhead, and resistance to quantum attacks. Therefore, we propose an efficient module-lattice-based certificateless online/offline signcryption (MLCLOOSC) scheme resistant to quantum attacks while meeting the confidentiality and unforgeability requirements under Type I and Type II attacks. Compared with five recent CLOOSC schemes, theoretical analysis, and experimental test results show that the proposed scheme outperforms the other five schemes regarding computational and communication costs and security. Therefore, our scheme is more suitable for application in IoMT scenarios.

The Internet of Medical Things (IoMT) plays a pivotal role in modern healthcare systems, enhancing patients’ medical experiences and improving the efficiency of public medical services. However, concerns regarding security and privacy may hinder the widespread implementation and development of IoMT in practical applications. Dynamic Searchable Symmetric Encryption (DSSE) can maintain search capabilities on encrypted data, even when files are dynamically added or deleted. Earlier DSSE schemes typically support only single keyword query and provide forward security under the assumption of semi-honest servers, which significantly limits their applicability in real-world scenarios. To resolve these limitations, we propose a forward-secure and verifiable DSSE scheme that supports multikeyword conjunctive query. Our scheme ensures forward security by utilizing a chain structure and guarantees correctness and completeness through RSA accumulator and Homomorphic Message Authentication Code (HMAC). Furthermore, we integrate the forward index and inverted index to enable efficient retrieval. Through comprehensive security and performance analysis, we demonstrate that our scheme effectively protects users’ privacy while maintaining low computation and communication overheads. Finally, some experimental evaluations are conducted to verify both the correctness and efficiency of the proposed scheme.

As Internet technology develops swiftly, the significance of privacy protection is escalating in the realms of e-commerce, e-government and software security. Due to the combination of the benefits of proxy signatures and blind signatures, the proxy blind signature scheme not only distributes the workload across application networks but also effectively safeguards the confidentiality of sensitive information. Additionally, the identity-based proxy blind signature protocol can avoid the problem of heavy certificate management and is widely used in electronic commerce and other scenarios. However, some identity-based proxy blind signature protocols that rely on the large integer factorization problem and the discrete logarithm problem are unable to withstand from attacks from quantum computers. Furthermore, current lattice-based proxy blind signature protocols offer only heuristic security and require three rounds of information exchange during the signing phase. In this paper, we introduce a new two-round identity-based proxy blind signature scheme based on lattices. This scheme utilizes a zero-knowledge proof protocol on lattices as its core component to develop an interactive two-round signature scheme that is free from security proof vulnerabilities. Additionally, we validate the security of the proposed protocol within the random oracle model and conduct a performance analysis.

The rapid evolution of the Industrial Internet of Things (IIoT) has driven unprecedented growth in industrial data volumes. To enhance cost efficiency and data-sharing capabilities, massive amounts of this data are stored in the cloud. Public Key Encryption with Keyword Search (PEKS) technology enables efficient encrypted data retrieval without key management and distribution issues and has been extensively studied for this purpose. However, due to inherent IIoT characteristics—such as heterogeneous data formats, resource-constrained devices, and heightened vulnerability to attacks, existing PEKS schemes face significant limitations: 1) typically restricted to single-keyword searches; 2) prohibitive computational overhead for resource-limited IIoT devices; 3) heightened risks of exploitation by attackers. To address these issues, we propose a lightweight certificateless authenticated encryption with multi-keyword search scheme, named CLAEMKS. It enables efficient multi-keyword search while substantially enhancing computational efficiency by eliminating the intensive bilinear pairing operations. Meanwhile, by leveraging certificateless cryptography, CLAEMKS solves certificate management problems while avoiding key escrow issues. Furthermore, formal security proofs and efficiency analyses are conducted to validate the effectiveness of our proposed scheme. The results demonstrate that CLAEMKS delivers substantial performance and security improvements.

Internet of Medical Things-based healthcare system (IoMTHS) is a kind of industrial information system that integrates life monitoring, pathological inference and drug therapy. However, the sensitive nature and high value of its data make it a prime target for cyberattacks. Although many multiserver authentication protocols have been studied in recent years to ensure that only authorized users can access medical services, new vulnerabilities are always identified and covertly utilized by the smarter adversary due to lack of continuous monitoring and dynamic authentication, reducing the trustworthiness of IoMTHS. To address above challenges, in this article, we propose a multiserver authentication scheme with integrated monitoring (MAIM) for IoMTHS, which achieves user locked access control by strictly and continuously binding system access permissions and user behavior. MAIM consists of a three-factor-based static authentication (TFSA) and a deep learning-based continuous authentication (DLCA). TFSA utilizes double-anonymity strategy to protect users’ privacy and track their malicious behaviors, and uses physical unclonable function (PUF) to protect the security of privacy information in users’ devices and servers, which achieves lightweight and three-factor secrecy. The DLCA trains a deep neural network to recognize the legitimacy of users based on the user behavior transmitted by their sensing devices. TFSA is provably secure under the random oracle model, whereas DLCA exhibits high feasibility with experimental accuracy reaching 100%.

The interconnected environment of the Internet of Vehicles (IoV) facilitates the development of various low-carbon and secure location-based services. However, sharing data with semi-trusted service providers poses serious security risks. In particular, it can threaten the confidentiality of past messages after the leakage of the user’s key. In this article, we propose an efficient and forward-secure conditional privacy-preserving scheme for IoV, namely, EFSC. We construct a cryptographic method with forward secrecy in the proposed EFSC scheme, which ensures the confidentiality of past messages even after the user’s secret key has been compromised. This method incorporates key derivation functionality and efficiently addresses the complex certificate management issue with the assistance of smart contracts. Additionally, the designed smart contract facilitates authentication. We analyze and prove that the proposed EFSC scheme satisfies the proposed privacy and security requirements with better security performance. We use Goerli, an Ethernet test network, to deploy customized smart contracts to prove its feasibility. Furthermore, the proposed EFSC scheme exhibits high-index generation and pairing efficiency and realizes less computational and communication overhead. Compared with the existing schemes, its computational overhead in message signing, signature verification, and user revocation can be reduced by up to 95.61%, 36.53%, and 67.01%, respectively. Moreover, the communication overhead for initiating a location service query is only 0.3760 kB. These results show that the proposed EFSC scheme has certain advantages regarding efficiency and security.

The anonymity of blockchain may be exploited by criminals for illegal fund transfers, thus a conditional privacy-preserving scheme is important for blockchain regulation. Currently, sharding technology under a multi-chain architecture is used to improve blockchain scalability. However, current conditional privacy-preserving schemes cannot work on this architecture. To protect the privacy of the transaction, we present a conditional privacy-preserving transaction scheme (MC-CPPT) for multi-chain blockchain system. In this system, we proposed a zero-knowledge proof based anonymous transaction, in terms of the identities of transaction participants and amounts, which also enables the unlinkability of transactions and indistinguishability between cross-chain and intra-chain transactions in multi-chain blockchain system. In addition, a multi-node regulatory agency is introduced to control the transaction amount and frequency in the system without a single point of failure. Moreover, an ECC-based encryption scheme is proposed to achieve the traceability of suspicious transactions. A security model is defined and the security of MC-CPPT is demonstrated to meet the expected security goals. Evaluating the prototype revealed acceptable performance and additional security features.

Permissioned blockchains play a significant role in various application scenarios. Applications built on heterogeneous permissioned blockchains need to migrate data from one chain to another, aiming to keep their competitiveness and security. Thus, data migration across heterogeneous chains is a building block of permissioned blockchains. However, existing data migration protocols across heterogeneous chains are rarely used in practice since data migration technologies are insecure. To this end, we propose a data migration protocol across permissioned blockchains, namedDataFly. We design apeg consensus mechanism, which provides consistent data-migration functionality between any two permissioned blockchains. To preserve the confidentiality of data, we invoke two classical cryptographic methods, i.e., i) ECDSA feature and ii) theintegrated signature and public key encryptionscheme. Through combining those two methods, data can be securely migrated from one permissioned blockchain to another without exposing the migrated data to anyone except associated parties. To demonstrate the practicality ofDataFly, we implement a prototype ofDataFlyusing existing popular permissioned blockchains, i.e., Hyperledger Fabric and private enterprise Ethereum. Measurement results demonstrate thatDataFlyoutperforms related works in terms of transaction latency and gas costs.

Ensuring cloud data security and reducing cloud storage costs have become particularly important. Many schemes expose user file ownership privacy when deduplicating authentication tags and during integrity auditing. Moreover, key management becomes more difficult as the number of files increases. Also, many audit schemes rely on third-party auditors (TPAs), but finding a fully trustworthy TPA is challenging. Therefore, we propose a blockchain-based integrity audit scheme supporting data deduplication. It protects file tag privacy during deduplication of ciphertexts and authentication tags, safeguards audit proof privacy, and effectively protects user file ownership privacy. To reduce key management costs, we introduce identity-based broadcast encryption (IBBE) that does not require interaction with key servers, eliminating additional communication costs. Additionally, we use smart contracts for integrity auditing, eliminating the need for a fully trusted TPA. We evaluate the proposed scheme through security and theoretical analyses and a series of experiments, demonstrating its efficiency and practicality.

In cryptography, side-channel analysis (SCA) is a technique used to recover cryptographic keys by examining the physical leakages that occur during the operation of cryptographic devices. Recent advancements in deep learning (DL) have greatly enhanced the extraction of crucial information from intricate leakage patterns. A considerable amount of research is dedicated to studying the SubByte (SB) operations of the advanced encryption standard (AES). This is because the SB process, which generates numerous transitions between 0s and 1s during encryption, results in significant energy leakage. However, traditional analysis models primarily focus on the initial round of SB operations in AES, which are less effective on mobile terminals where it is difficult to collect enough signals. These models often neglect additional operations and subsequent rounds, thus providing limited insights from small datasets. Consequently, this limitation has a direct impact on the accuracy and efficiency of key recovery. Our study uses$\rho $-test analysis to show that significant leakage occurs not only during the S-box operation but also during the AddRoundKey (AR) phase of AES. To address these challenges, we propose a new SCA method, that is, optimized for small sample sizes. This method includes a new comprehensive round trace labeling algorithm, which simultaneously analyzes the SB and AR stages of each AES round. Additionally, we introduce the peak precise localization algorithm to accurately identify the points of energy leakage during each encryption round. Our experiments, conducted with power and electromagnetic (EM) datasets from the STM32F303 microcontroller, demonstrate that our method can reliably recover keys with as few as 20 traces. These results highlight the enhanced capability of our method in handling the complexities of small sample datasets in cryptographic analysis.

The development of cloud computing needs to continuously improve and perfect the privacy-preserving techniques for the user’s confidential data. Multi-user join query, as an important method of data sharing, allows multiple legitimate data users to perform join query over the data owner’s encrypted database. However, some existing join query protocols may face some challenges in the practical application, such as practicality, security, and efficiency. In this article, we put forward a dynamic and secure join query protocol in the multi-user environment. Compared with some existing protocols, the proposed protocol has the following advantages. On the one hand, we utilize the dynamic oblivious cross tags structure to realize an efficient join query with forward and backward security. On the other hand, we combine the randomizable distributed key-homomorphic pseudo-random functions with join query to support multiple data users, which can provide resilience against the single user’s key leakage and resist collusion attacks between the cloud server and a subset of data users. We formally define and prove the security of proposed protocol. In addition, we give a detailed analysis of computation and communication overheads to demonstrate the efficiency of proposed protocol. Finally, we carry out some experimental evaluations to further demonstrate the superiority of functionality and efficiency.

In the Vehicle-to-Everything (V2X) communication system, the presence of ambiguous warnings significantly increases the risk of severe accidents, posing a substantial threat to the safety of autonomous driving. It is crucial to detect such confusing warnings to avoid danger. Existing solutions to address this issue heavily rely on trust entities or are constructed based on number theory assumptions, leading to low efficiency and vulnerability to quantum attacks. In this paper, we leverage the double authentication-preventing signature scheme (DAPS) to present a revocable identity-based double-authentication preventing signature scheme (RIDAPS) and provides an instantiation from lattice. Furthermore, we propose a post-quantum secure misbehavior preventing scheme (Misp) based on our RIDAPS scheme. We give a detailed proof in the random oracle model (ROM) to demonstrate that our contribution achieves security requirements. Additionally, the efficiency evaluation results demonstrate that our scheme is suitable to be applied in V2X.

Artificial intelligence (AI) on edge refers to combining edge computing and AI, and enjoys the benefit of distributed structure, intelligence, and timeliness. Specifically, natural language processing model, which allows to processing language data right close to the device location within milliseconds and providing intelligent controller, have revolutionized researches. Recently, privacy concerns spiked when it is applied in healthcare, autonomous vehicles, manufacturing, etc. Secure multi-party computation has the advantage of strong security guarantee and computability over multi-sourced data. However, it is challenging to translate the timeliness benefit of Edge AI to secure deployment, as only constrained computation and storage resources are available for the edge nodes. We focus on the natural language processing (NLP), and design an efficient secure three-party computation protocol (called QuickNLP) in the semi-honest setting tolerating one corruption. Specifically, for the non-linear operations, we adopt the constant-round distributed comparison function (${\sf DCF}$) to evaluate the piecewise function efficiently with high accuracy. The proposed framework has been experimented with Python and the results show that QuickNLP could be a valuable solution for data privacy in edge computing. Specifically, compared to the existing protocol, we improve the computation costs by a factor of roughly$7\times$.

With the rapid development of vehicular ad-hoc networks (VANETs) and the increasing diversification of user demands, interactions between different management domains have become more frequent. Identity authentication is an effective way to establish cross-domain trust and secure communication. However, the existing cross-domain authentication schemes of VANETs are limited to the same management or authentication technology for each domain and rely on centralized cross-domain identity management. Even distributed management solutions encounter latency sensitivity, security and privacy challenges. To address these challenges, we propose a blockchain-assisted revocable cross-domain authentication scheme for VANETs. The proposed scheme can establish trust between domain entities by deploying different authentication methods and using distributed management to avoid single-point failures. In addition, the scheme can revoke the identity of malicious vehicles by updating the group public key, thereby ensuring the security and privacy of cross-domain Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communication. This design avoids the additional impacts of blockchain technology constraints on the high mobility and real-time requirements of VANETs. Security analysis and performance evaluation show that our scheme can resist more attacks and has better security than other related schemes while also achieving a better balance between communication and computational cost.

The e-vote is regarded as a way to express the opinion that the voters ask for. Actually, the e-vote could be applied wildly like questionnaire, survey and feedback. Moreover, the coexistences of efficiency and security as well as transparency and privacy could be considered as building blocks in the e-vote system. The blockchain could provide a public access board to reduce the storage costs for the field consisted of the vote group manager (GM) with its vote assistants (VA). Particularly the$k$-times anonymous authentication ($k$-TAA) could also be a practical approach to preserve voters’ privacy and reduce the computation costs during the vote process. However, the e-vote scheme with pure$k$-TAA strategy could damage either the supervision of voting or the efficiency and consistency of authentication process. What’s more, the impacts of dishonest voters couldn’t be stopped until the vote end. To tackle these problems, we apply the accumulator technology to add or revoke the voters at any time and extend the framework of$k$-TAA with the update process for the e-vote on blockchain for supervision ($ k$-TEVS). In our scheme, the voter updates his membership witness and proves the fact that he is still a valid member with respective VA under the latest accumulator value. What’s more, this witness update operation is not contained in the authentication process, which means that the authentication process is still constant and efficient. Moreover, our add or delete update process with signature of knowledge needs only one pairing operation. For the security, we prove that the relaxed anonymity still holds in the$ k$-TEVS framework. Finally, We implement$ k$-TEVS scheme, the Emura’s work [1] and the Huang’s work [2] for comparison. Then we make time cost and communication cost experiments, which present the feasibility and practicality of this scheme.

The network architecture of modern vehicles is composed of multiple communication protocols and electronic control units (ECU). Compared to the widely used protocol of Controller Area Network (CAN), CAN with Flexible Data-Rate (CAN-FD) protocol is suitable for applications requiring higher data throughput. However, the CAN-FD bus is vulnerable to intrusion by external attackers. Nowadays, several secure mechanisms have been proposed to protect the security of in-vehicle data. However, there are still two issues: 1) Most schemes use a centralized controller for key distribution, which can easily lead to a single point of failure; 2) The existing key management modes are not suitable for real-world CAN-FD networks in vehicle manufacturing. To address these issues, we propose a lightweight semi-decentralized scheme based on Database CAN (DBC) files to secure in-vehicle communication. ECUs are grouped on the send-receive relationships set in the DBC file, considering both the communication mode and sending efficiency. Furthermore, the proposed scheme overcomes reliance on long-term keys. Moreover, the security is analyzed by the random oracle model. The performance analysis is evaluated on microcontroller units (MCU) STM32H743IIT and Raspberry Pi 3B. The proposed scheme optimizes the computational costs of authentication, key agreement, and secure communication stages by up to 97.89%, 99.95%, and 82.35%, and optimizes the communication costs by up to 75.52%, 98.42%, and 29.41% compared to existing methods. Simulation experiments demonstrate that the bus load of the scheme increases by up to 9.84% compared to the baseline network.

Secure aggregation of medical data enables detailed data analysis and informed medical decision-making in e-health systems, optimizing data resources utilization and enhancing service quality and decision accuracy. However, the collection of large volumes of medical data poses a significant risk of privacy leakage. Most existing privacy-preserving data aggregation schemes focus on additive aggregation of single or multi-dimensional data, which greatly limits their applicability. This article introduces a blockchain-based multifunctional data aggregation (BM-PDA) scheme for e-health systems. First, BM-PDA supports overall aggregation queries of data samples and can compute the maximum and minimum values within these samples. Second, it enables selective data aggregation queries based on various user attributes. Furthermore, analysis shows that integrating these two algorithms protects both user’s private data and attribute data. Performance evaluations indicate that the computational and communication costs are acceptable, demonstrating the scheme’s practical applicability.

Blockchain systems have evolved over decades, addressing the inefficiencies and high costs associated with centralized architectures. Among various consensus mechanisms, committee-based hybrid Byzantine Fault Tolerant (BFT) protocols are a fundamental approach to blockchain consensus. However, designing a hybrid BFT consensus protocol that ensures fairness, responsiveness, and formal security remains challenging. In this paper, we propose GRBFT: a Gaussian reputation-based hybrid BFT blockchain consensus protocol with a formal security framework. Our proposed protocol integrates a multilateral Gaussian reputation evaluation to incentivize trusted nodes' participation in the consensus. We use threshold signatures and verifiable random functions (VRFs) to randomly select committee members and leaders, ensuring fair reconfiguration and unbiased sortition. A formal security framework is utilized to design and analyze the blockchain consensus system. Additionally, we design a speculative GRBFT (S-GRBFT) protocol to circumvent the traditional$\mathcal {O}(n^{2})$leader sortition complexity and reduce the communication to$\mathcal {O}(n)$within a single round. Moreover, we present a secure candidate committee reconfiguration method that efficiently updates members based on their reputation and a Proof-of-Stake (PoS) mechanism. The proposed GRBFT protocol is proven to achieve consistency and liveness under the corruption and liveness parameters.

In the era of flourishing sustainable smart cities, with the accessibility of Internet and the persistent evolution of distributed computing, there is an increasing reliance on cloud/fog computing environments and online data storage platforms for secure data sharing. However, existing cryptographic schemes fall short in simultaneously satisfying security requirements such as bilateral fine-grained access control, resilience to quantum attacks, assurance of the authenticity of decrypted data, and forward security for historical data. To tackle these challenges, we propose the innovative puncturable attribute-based matchmaking encryption scheme based on lattice cryptography. The method adeptly satisfies the aforementioned stringent security requirements concurrently, offering a triple-layered assurance for the secure implementation of secret sharing. The receiver, unable to successfully decrypt, remains uninformed about any specifics regarding ciphertexts and the access policy. Our PM-ABE scheme has manifested resilience against quantum attacks, collusion attacks, chosen plaintext attacks and ensuring unforgeability under chosen message attacks. Furthermore, our comprehensive efficiency analysis substantiates that our scheme maintains a favorable level of computational efficiency and storage consumption.

Introducing the SDN paradigm can further improve the handover efficiency of mobile nodes, and researchers have proposed corresponding solutions to the security problems in the handover process. Some existing cryptography-based schemes delegate authentication to the fog nodes to accelerate the handover process, however, the computation and communication overheads are not low enough to satisfy the requirements of delay-sensitive vehicular applications. To realize secure handover of vehicles in software defined vehicular networks (SDVN), in this paper, based on symmetric cryptography, we propose a lightweight and secure handover scheme with conditional privacy-preserving for group-based SDVN. The handover authentication only involves lightweight operation, without based on elliptic curve cryptography or involving complex bilinear pairing operations. After successfully authenticating with the SDN controller, the vehicle can directly authenticate with the fog nodes in the same group. The polynomial and one-way hash chain are used to realize group key update. We use BAN logic and ProVerif to formally analyze and test the security of our scheme. The detailed security analyses show that the scheme can resist common types of attacks and meet the essential security and privacy requirements. Compared with other related and represented works, our scheme exhibits better performance in computation and communication overheads.

The rapid growth of electric vehicle and autonomous vehicle populations has led to explosive expansion of IoV data being transmitted in the wireless communication infrastructure. Advances in IoV technologies also resulted in more complex and dynamic communication protocols/patterns, which are hard for the underlying wireless network to satisfy. Besides, security considerations of IoV communications require that key management must be stringently prohibit global failure mode of key management, meaning that, if a single IoV node compromises its private key, it will not lead to total security failure of the entire IoV network. To address these issues, in this paper, we propose a heterogeneous parallel key-insulated multi-receiver signcryption scheme for IoV (HPKI-MRSC). Firstly, the proposed scheme can realize one-to-many heterogeneous transmission, in which RSUs are deployed on certificateless cryptography (CLC) system, while vehicles are allocated in identity-based cryptography (IBC) system. In this manner, we observe that message transmission efficiency is improved greatly. Secondly, the parallel key-insulated mechanism can employ two helper keys to update private key periodically, and then solve key disclosure problem. Finally, when the number of receiver n is greater than or equal to 3, the proposed scheme has a lower signcryption overhead than other comparative schemes, and thus it is more suitable for IoV.

Due to the rising requirement for data sharing, multi-data owner access control schemes have emerged, where a single data file is jointly owned by multiple data owners. Since the shared files contain information from multiple data owners, it is crucial to revoke malicious users to minimize harm when data leakage occurs. However, current multi-data owner solutions typically rely on a single data owner to encrypt and share data and fail to provide robust user revocation. When revocation is managed by a single entity, it may fail to protect the rights of all data owners and can introduce a single point of failure in multi-data owner settings. On the other hand, if revocation requires the participation of all data owners, user access may fail if some owners are offline or compromised. To address these issues, we propose a robust multi-data owner access control scheme with efficient user revocation. We construct a secret resharing protocol based on secret sharing technology and proposed a multi-data owner access control scheme. Only users who obtain a sufficient number of private keys can decrypt the ciphertext. To achieve multi-owner controlled revocation, we use key splitting to divide the user’s private key into an authorization key and an update key and embed a period into the update keys. During user revocation, the cloud updates the ciphertext and the data user can decrypt the ciphertext without obtaining the update keys of all data owners. The thorough performance analysis shows that the overhead of the proposed scheme is acceptable. Specifically, the proposed scheme takes approximately 0.5 seconds to encrypt, and with preprocessing, this time is reduced to 0.06 seconds, while decryption requires around 0.15 seconds on the Raspberry Pi.

In vehicular networks, caching service content on edge servers (ESs) is a widely accepted strategy for promptly responding to vehicle requests, reducing communication overhead, and improving service experience. However, implementing such an architecture requires addressing the challenges associated with ES response data reliability and communication security. In this study, to tackle the ES response data reliability issue, a blockchain-assisted threshold signature scheme for cache-based vehicular networks is proposed. The scheme utilizes a threshold mechanism to sign the data broadcast by the ES, incorporates blockchain to trace malicious signers, and avoids the shortcomings and limitations associated with idealized assumptions for the ES in existing data-sharing schemes. Moreover, considering the communication security and high-speed mobility of vehicles, using the non-interactive signatures of knowledge based on the Σ-protocol, a secure and efficient message authentication scheme for vehicles and ESs is provided. Through rigorous security proofs and comprehensive analyses, our scheme satisfies the communication security requirements of vehicular networks. By leveraging the JPBC library for performance analysis, the proposed scheme demonstrates advantages as concerns both computation and communication overheads compared to related schemes. Moreover, we implemented the proposed scheme on an Ethereum test network (i.e., Goerli) to validate its feasibility.

Vehicular ad-hoc networks (VANETs) are the cornerstone of intelligent transportation systems, designed to enhance road safety and traffic efficiency. However, their dynamic and distributed nature poses significant challenges for secure communication and key management. Traditional authentication and key agreement (AKA) schemes for VANETs often rely on centralized trust architectures, resulting in system security and reliability issues. Despite the introduction of distributed trust architecture schemes that have appeared recently, they fail to solve one issue, i.e., how the key agreement requests can be authenticated in the distributed communication scenario where the authentication authorities are all non-full-credible and have differentiated credibility. To solve this issue, we propose a hierarchical AKA scheme for VANETs with cloud-edge collaboration powered by consortium blockchain. Specifically, we first proposed a vehicle reputation evaluation algorithm for evaluating the trustworthiness of the vehicle, so that the AKA requests sent by vehicles with low reputation will be rejected. On the basis of the reputation evaluation algorithm, we proposed a hierarchical threshold-based AKA scheme for VANETs where cloud servers (CSs) and edge servers (ESs) can collaboratively authenticate the AKA requests, so that the authentication service can be trusted upon getting authenticated by a series of valid combinations of CSs and ESs. Both formal and informal security proofs validate the security of our proposed scheme, and simulation experiments demonstrate its efficiency.

Cloud computing has become the predominant platform for data sharing due to its adaptability, cost-effectiveness, and ability to scale resources according to user demand. Ensuring secure and efficient data sharing has long been a central research focus, with attribute-based encryption (ABE) serving as a key cryptographic primitive. In real-world scenarios, user attributes often change, necessitating timely revocation of access rights. Common user revocation methods include direct and indirect revocation. Direct revocation is controlled by the data owner, who adds revocation information to a list and embeds it into ciphertext to revoke permissions. Indirect revocation is managed by an authorized authority or delegated third party, dynamically publishing revocation information and generating new keys and ciphertexts. Conventional direct and indirect revocation methods incur substantial communication and computation overheads, limiting their practical effectiveness, particularly in environments with frequent user access terminations. To address these challenges, we propose a novel puncturable ciphertext-policy ABE scheme based on lattice cryptography for user revocation, eliminating the need for key regeneration and revocation-list maintenance. The proposed approach effectively resists collusion, quantum, and chosen-plaintext attacks, and experimental evaluations demonstrate its advantages in storage consumption, communication cost, and computational overhead.

The rapid evolution of the Industrial Internet of Things (IIoT) has necessitated increased device interactions across various management domains. This entails devices from different domains collaborating on the same production task. This poses significant challenges for the dynamics of cross-domain authentication schemes. Traditional cross-domain authentication schemes struggle to support seamless switching between domains and face difficulties when accommodating devices that join and leave the same domain. Moreover, these schemes suffer from intricate interactions and suboptimal efficiency. To address these issues, we propose a dynamic group signature scheme based on a dynamic accumulator and a non-interactive zero-knowledge proof. We integrated this scheme with blockchain technology to construct an efficient revocation cross-domain authentication scheme. The proposed scheme enables cross-domain anonymous authentication with simple interactions and provides an efficient revocation function for illegal devices. This approach ensures conditional privacy-preserving and enables efficient member joining and exiting through a dynamic accumulator. It effectively addresses the dynamic requirements of devices involved in IIoT production and manufacturing processes. We prove the security of the proposed scheme using a random Oracle model and conduct thorough analyses to verify its resistance against various attacks. Furthermore, the experimental results demonstrate that the proposed scheme achieves better performance in terms of computational and communication costs.

Efficient and secure data sharing in the Internet of Vehicles (IoV) is critical for the advancement of intelligent transportation, particularly in the context of emerging 5G/6G networks and driverless technology. This has prompted researchers to explore Blockchain-based Internet of Vehicles (BIoV) solutions to address common issues in intelligent transportation systems (ITS). However, at the edge layer, existing reputation and consensus mechanisms in the BIoV model face challenges such as significant energy consumption, limited scalability, and pronounced centralization. To tackle these issues, we introduceTRCO, a Permissioned Blockchain-basedTrusted andRobustConsensusOptimization orienting ITS.TRCOis a three-layer BIoV architecture applicable to any BIoV scenario, offering robust scalability with the addition of new sub-regions. To improve the quality of data sharing for edge layer, we propose a decentralized reputation evaluation mechanism and integrate PoS and PBFT consensus algorithms to enhance performance by evaluating the communication behavior of edge servers. Security analysis and simulation experiments demonstrate thatTRCOachieves high scalability and reliability, effectively filters Byzantine edge servers, and enhances the decentralization and consensus efficiency of the system.

Vehicular intrusion detection systems (VIDSs) play a crucial role in protecting the security of vehicular ad hoc networks (VANETs). Recently, numerous researchers have proposed effective vehicular intrusion detection systems to protect the security of VANETs. However, some existing vehicle intrusion systems are susceptible to catastrophic forgetfulness in the process of implementing incremental updates to target novel attacks. Other solutions lack consideration for the continuous updating capabilities of vehicle intrusion detection systems. It is worth mentioning that in the real world, the network attacks suffered by vehicles are not constant, and fixed intrusion detection systems may struggle to detect new network attacks effectively. To address these challenges, we propose an incremental learning-based vehicular intrusion detection scheme that supports continuous updating of the intrusion detection system. Specifically, we design a sample gradient optimization algorithm to enhance the data quality of training samples. Additionally, we utilize locally stored historical data to balance the number of old attack classes for model distillation, thus mitigating the problem of forgetting the old classes as the model learns new classes. The comprehensive experimental results on the CICIDS2017, TON_IOT, and Veremi datasets demonstrate that the proposed vehicular intrusion detection system maintains superior detection accuracy during continuous updating and surpasses the state-of-the-art solution.

Owing to frequent traffic accidents, the violation reporting service is a promising method to enhance road safety in vehicular ad hoc networks (VANETs). However, to implement such a service, it is critical to ensure security, privacy, and efficiency when vehicles send messages to roadside units (RSU). In this study, to address these issues, a vehicle violation reporting service is proposed using reputation systems and a physically unclonable function. The proposed scheme ensures secure authentication between vehicles and RSUs, facilitates an efficient search for invalid signatures, and overcomes the limitations present in ID-based conditional privacy-preserving authentication schemes. Moreover, considering the dynamic VANET environment, the distribution of invalid signatures may vary across multiple scenarios. Therefore, a fault-tolerant mechanism is proposed to ensure the robustness of this approach. Security proof with the random oracle model and detailed security analysis proved that the scheme could satisfy the security requirements of VANETs. Our scheme outperforms related approaches in terms of authentication overhead and the identification of invalid signatures, achieving superior performance in both aspects.

The rapid development of network technology has allowed numerous vehicular applications to be deployed in vehicles, thereby enriching the driving experience of users. However, the openness of vehicular networks enables attackers to launch network attacks on vehicles through network ports, leading to the destruction of vehicular networks. To develop an intrusion detection system suitable for distributed vehicular networks, researchers have utilized federated learning to train detection models. Nevertheless, most federated learning-based vehicular intrusion detection systems seldom consider rapidly updating the detection model and fail to detect unknown attacks effectively. In this study, we propose a federated learning-based vehicular intrusion detection system that fully considers the traffic characteristics of multiple network regions and selects representative clients to participate in model aggregation, thereby accelerating the convergence of the global model. Furthermore, to enhance the robustness of the detection system, we utilize extreme value theory and multilayer activation vectors to construct an unknown attack discriminator that can determine whether a network flow is an unknown attack. Comprehensive experiments on three open datasets demonstrate that the proposed intrusion detection system can quickly update and effectively identify known/unknown attacks in open vehicular networks

With the widespread deployment of vehicular ad-hoc networks (VANETs), data sharing has garnered considerable attention as a core feature of VANETs. Attribute-based proxy re-encryption (ABPRE) enables fine-grained access control and provides flexible ciphertext updates. The initially authorized vehicle generates the re-encryption key to enable ciphertext-to-ciphertext conversion in the cloud, allowing ciphertext to be shared with new recipients. However, initially authorized vehicles may not always be trustworthy and could share data with malicious receivers. In addition, the computation and communication overhead of ABPRE hinders its widespread application in VANETs. To address these issues, we propose a lightweight sanitizable scheme for edge-assisted VANETs based on ABPRE. In this scheme, the re-encryption key is verified by a sanitizer, to prevent the data from being shared with malicious data receivers. In addition, key-splitting techniques and edge computing are employed to reduce the communication and computation overhead of re-encryption. A comprehensive security analysis and performance evaluation demonstrate that the proposed scheme is efficient and practical.

Cryptocurrencies possess a natural advantage in financial applications where response time is not critical, given the well-known high latency and low throughput of blockchain technology. However, a notable gap exists in cryptocurrencies, specifically the absence of applications intentionally introducing delays in committing transactions to facilitate potential revocation operations. Large-Value Payment (LVP), a vital component in financial services, addresses this gap by enabling users to perform such operations. In this context, the payer retains the ability to revoke any number of payments within a pre-agreed timeframe T, while the payee gains the unrevoked transactions after T. In the blockchain landscape, trusted third-party platforms play a role analogous to traditional banking institutions, which can trivially realize LVPs. However, their centralized structure poses challenges such as a single point of failure, privacy concerns, and high transaction fees. Motivated by these limitations, we propose trustless large-value payment protocols with key characteristics: (i) trustlessness, eliminating reliance on any trusted party; (ii) revocability, allowing the payer to revoke payments within the predefined time; and (iii) universality, compatible with all current cryptocurrencies. In this paper, we formally define the semantic and security model of LVP, which paves the way for a new research direction. Building on this foundation, we present a straightforward yet efficient construction of LVP based on Bitcoin scripts. To overcome script-dependency limitations, we introduce a scriptless LVP protocol based on verifiable timed signatures and adaptor signatures. This achieves universality across different cryptocurrencies. We prove the security of our proposals in the Universal Composability framework and further enhance performance for multiple LVPs across diverse cryptocurrencies. Specifically, we design a protocol for secure witness reuse and employ verifiable timed discrete logarithm for revocability. Rigorous security analysis and performance evaluation confirm that both scripted and scriptless LVP protocols meet essential security objectives, providing practical solutions for users requiring transaction revocation without relying on trusted parties.

Committee-based blockchain consensus is a fusion of permissionless consensus and the permissioned Byzantine Fault- Tolerant (BFT) classical protocol. However, three enduring challenges remain: the formal framework for the Proof-of-Stake (PoS)-based hybrid consensus, the dynamic adjustment of committee size and the definition of consensus time-bound. To tackle these challenges, in this paper, we present a Stackelberg game-driven fair committee-based blockchain consensus protocol, dubbed SG-FCB, which combines PoS and reputation-based blockchain hybrid BFT consensus. The SG-FCB protocol lever-ages an unbiased BLS-threshold signature and a random shuffle algorithm to achieve fair leader election and committee reconfiguration seamlessly. Specifically, the variant-BFT is designed to maintain the low communication cost of$\mathcal{O}(n)$, and a Stackelberg game-based incentive mechanism is proposed to jointly maximize the individual profit of the validators and the expected consensus committee responsiveness efficiency of blockchain user. Rigorous security analysis shows that for an adversary with a stakeholding fraction less than 1/3 and sufficient reputation value, we define the time bound for consensus, and the SG-FCB protocol achieves consistency and liveness properties by reasonably setting a corruption parameter and liveness parameter within a formal framework.

Abstract Cloud storage has been widely used in remote data management, although correct storage of the outsourced file is still challenging in practice. Proofs of Retrievability (PoRs), a storage-oriented cryptographic tool, support integrity checking and efficient retrieval of the file. However, due to the lack of a fully credible oversight mechanism or a serious dependence on a trusted third party, most PoRs are incapable of achieving essential and straightforward trust between participants (i.e. the client and server). While blockchain shows promise in solving this trust issue, existing blockchain-based storage systems are scenario-constrained as they require private/permissioned or special-construct blockchains. Consequently, none of these systems provide robust and decentralized trustworthiness. We propose a general Blockchain-based Automatic Audit (BAA) scheme for PoR without limitations based on specific blockchain types. Specifically, we present BAA via stitching together a carefully designed or chosen array of sub-components such as storage proofs and Turing-complete smart contracts. We also integrate BAA with specific PoR models to prove its strong generality and availability. To our best knowledge, our proposal is the first blockchain-based approach that enhances traditional PoR models with both automatic audit and fair payment. The final analysis and implemented prototype on Ethereum demonstrate the utility of BAA.

Abstract After the Ethereum DAO attack in 2016, which resulted in significant economic losses, blockchain governance has become a prominent research area. However, there is a lack of comprehensive and systematic literature review on blockchain governance. To deeply understand the process of blockchain governance and provide guidance for the future design of the blockchain governance model, we provide an in-depth review of blockchain governance. In this paper, first we introduce the consensus algorithms currently used in blockchain and relate them to governance theory. Second, we present the main content of off-chain governance and investigate two well-known off-chain governance projects. Third, we investigate four common on-chain governance voting techniques, then summarize the seven attributes that the on-chain governance voting process should meet, and finally analyze four well-known on-chain governance blockchain projects based on the previous research. We hope this survey will provide an in-depth insight into the potential development direction of blockchain governance and device future research agenda.

Several studies have introduced edge computing and blockchain into the Industrial Internet of Things (IIoT) to satisfy the requirements of delay-sensitive applications and support cross-domain authentication. Although there have been many protocols to ensure the security and privacy of devices in the IIoT, existing protocols still suffer from problems. Updating keys and pseudonyms of devices by a trusted third party (e.g., certificate authority) will cause high communication and computation overhead, especially when the number of devices becomes much larger. Furthermore, an increasing number of transactions also cause high storage overhead on the blockchain. Therefore, we propose a blockchain-based cross-domain authentication protocol. Specifically, we propose a privacy-preserving method based on pseudonyms that offloads the task of generating pseudonyms from a trusted third party to edge servers to ensure the conditional anonymity of the devices. The device is allowed to request pseudonyms in bulk to reduce the number of transactions, thus reducing the storage overhead on the blockchain. Security analysis and experimental results demonstrate that our scheme achieves an efficient tradeoff between security and efficiency.

With the application of blockchain in Internet of Things (IoT), various IoT scenario-oriented blockchains have been proposed, meaning that multichain future within IoT ecosystem is growing. Cross-chain interoperability thus is essential. Sidechains is one of the crucial technologies for cross-chain interoperability, which allows blockchains to interoperate with each other. However, sidechains encounters practicability challenges impeding adoption, such as poor generality and inefficiency. In this article, we propose practical and secure sidechain construction (PSSC)in the form of parent-child chains, a practical and secure sidechains construction for heterogeneous blockchains orienting IoT scenarios. To achieve practicability, we first utilize succinct noninteractive argument of knowledge (SNARK), which is succinct noninteractive proof (arguments) of knowledge, to reproduce the state transition of blockchains, so that PSSC can get rid of the constraints on consensus mechanisms of blockchains; we then design an impawn-punish mechanism based on smart contract, which transfers the work verifying SNARK proof from mainchain to sidechain, preventing fork threat to mainchain. Due to employing SNARK based on recursive proof composition to generate cross-chain proof, our PSSC is more efficient with succinct cross-chain proof, reducing the overhead of storage of nodes. Besides, we formally prove our PSSC satisfies the three fundamental security properties of sidechains: 1) persistence; 2) liveness; and 3) firewall. Finally, we develop a proof-of-concept implementation of PSSC, and the experimental results show that the proof size of PSSC is about 28.8 kB, which is roughly$2094\times $,$9.36\times $,$6.56\times $,$4.23\times $, and$3.27\times $smaller than BTCRelay proof, PoW sidechains proof, PoS sidechains, zkRelay proof, and fast sidechains, respectively.

The emergence of 5G/6G networks has sparked new potentials for Internet of Things (IoT) scenarios, such as vehicle ad hoc networks (VANETs), inspiring numerous scholars to leverage Blockchain-based Internet of Vehicles (BIoV) solutions to address prevailing issues in VANETs. However, the dynamic and decentralized nature of VANETs presents significant challenges in terms of security and privacy, hindering data providers from engaging in the data-sharing process. Furthermore, the reliability of edge nodes and system architecture in the BIoV paradigm faces several challenges, including limited consensus participation, high resource consumption, poor scalability, and centralization. To mitigate these challenges, we propose RTSP, a robust and trusted service protocol for VANETs, based on a distributed ledger technology. RTSP advocates a novel three-tier BIoV architecture suitable for any permissioned BIoV application scenario. To improve the quality of data sharing, we design a decentralized reputation mechanism. This mechanism mitigates the performance bottleneck induced by consensus transactions by measuring the historical behavior of roadside units (RSUs). Empirical evidence from simulation experiments and security performance analyses substantiates RTSP’s capabilities. It can hinder the number of faulty RSUs from increasing while simultaneously improving data-sharing efficiency, simplifying communication complexity, and enhancing system scalability and consensus stability.

Providing high-quality network services for vehicles is a challenge because of the fast-moving character of the vehicles. To address the shortcomings of traditional centralized and distributed mobility management schemes, such as triangular routing and poor scalability, many researchers use software-defined networking (SDN) to build mobility management schemes. However, most schemes rarely consider how to select the optimal base station for high-speed mobile vehicles in a dense network environment. Only using the received signal strength to select the base station tends to cause a ping-pong effect. Moreover, due to the high mobility of vehicles, the routing updates between vehicles and communication nodes will frequently occur, resulting in the significant consumption of network resources. In this article, we propose a mobility management scheme MM-SDVN based on SDN for vehicles. MM-SDVN uses deep Q-network to construct the optimal base station selection model, designs a multipath prefix matching algorithm to reduce the cost of route update, and realizes the seamless handover of vehicles in SDN intradomain and interdomain scenarios. The comprehensive experimental results show that MM-SDVN greatly improves the network service quality and handover performance of the vehicle. Compared to the other schemes, MM-SDVN improved vehicle throughput by 6.14%, 8.85%, and 10.34%, respectively.

Car sharing is gaining increased popularity in urban transportation which allows individuals to conveniently rent vehicles for short periods. Such systems, however, present considerable challenges to security such as unauthorized access and privacy data breaches, as service providers are able to track the precise mobility patterns of all customers. Nevertheless, efforts in solving the security and privacy concerns associated with car-sharing services are relatively few, in particular for a trade-off between privacy preservation and accountability of misbehaviors. In this work, we propose an efficient Privacy-Enhancing and Accountable Car Sharing System (PEACS), introduced to mitigate the aforementioned threats. PEACS primarily employs several key ingredients, including structure-preserving signatures on equivalence classes (J CRYPTOL’s 19), as well as two primitives designed in this paper, namely: signatures of knowledge and identity-based structure-preserving signatures with a tag on equivalence classes. Furthermore, we employ a bivariate polynomial function to establish a revocation mechanism that ensures accountability. We provide thorough security proof to demonstrate the security and privacy of PEACS. Comprehensive performance evaluation and comparison results point out that our proposed scheme is feasible in practical settings.

Range query is commonly used to support ciphertext retrieval on encrypted databases in a cloud-based environment, and order-revealing encryption (ORE) plays an increasingly important role in range query for ciphertext field processing. Specifically, one can utilize ORE to facilitate comparators to determine whether the order of ciphertext(s) corresponds to the associated plaintext(s). Newer ORE designs include those that are resistant to common attacks (e.g., spectral attacks) and those that are capable of supporting both multi-client and single-client settings. However, in the scenario of cross-database range queries, existing multi-client ORE approaches generally pass the data owner’s query key to the searcher during the authorization process. Consequently, this results in agent transfer and permission extension, which can be exploited to facilitate unauthorized access to the database data. To solve these limitations, we propose om-ORE. The latter uses the oblivious pseudorandom function (OPRF) protocol to further enhance the security of token generation mechanism in ORE, and is designed to ensure that neither the data owner nor the authorized client reveals any secret key or expected query range to each other. Using the proposed om-ORE scheme as a building block, we design a secure multi-client ciphertext range query scheme that is resilient to both agent transfer and permission extension attacks. The performance evaluation shows that om-ORE inherits the advantages of state-of-the-art multi-client ORE approaches, in terms of ciphertext size and comparison efficiency, as well as having comparable performance in the token generation process.

In the Industrial Internet of Things (IIoT), data sharing is crucial for promoting the intelligent development of industrial production. To achieve effective data supervision, introducing blockchain into traditional cloud-based data-sharing frameworks has attracted widespread attention. However, existing blockchain-based data-sharing schemes still have issues with security and efficiency. Therefore, we propose a blockchain-enabled data-sharing scheme based on proxy re-encryption. First, the scheme considers both storage and access authentication, guaranteeing data sources’ trustworthiness and preventing data misuse. Second, the scheme uses an on-chain and off-chain cooperative storage mechanism, saving the storage resources of the blockchain. Third, the scheme supports data packing, which effectively improves data storage efficiency. The security analysis shows that our scheme satisfies the security requirements. Finally, we build a blockchain platform using the hyperledger fabric. The performance evaluation shows that our scheme is more advantageous regarding computational overhead than other related schemes.

In vehicular ad-hoc networks (VANETs), existing traffic accident handling schemes are adoptable only in the scenario with roadside unit (RSU) deployment, and the generation of accident reports relies on RSUs and witness vehicles. Without the confirmation from involved vehicles in the accident, it will probably cause disputes afterward, and RSU captured attacks may also affect authentication of vehicles and correctness of accident reports. To address the above issues, we propose a vehicle to vehicle (V2V) and vehicle to RSU (V2R) authentication and traffic accident handling protocol, in which accident vehicles are sufficient to generate accident reports, thereby enhancing autonomy of the vehicular communication system and reducing reliance on external infrastructure. Furthermore, for ensuring integrity and traceability of accident reports, we utilize blockchain to keep registration information and jointly signed reports, which realizes efficient and secure mutual authentications in V2V and V2R protocols. Finally, for preserving privacy of vehicles, we integrate elliptic curve cryptosystem (ECC) and symmetric encryption to design a dynamic pseudo-identity strategy, which still allows the registration center to track malicious vehicles. The formal security proof and comparative analysis validate that our protocol preserves higher security and lower overhead by comparison with related schemes.

There is a growing concern about the complete lifecycle security of data in Internet of Things (IoT). This may cause privacy and trust problems for users regarding data sources, data storage, and access control for data sharing. Blockchain is a valuable solution to the above problems through distributed ledger technology, and it has been widely applied in various fields such as public services, finance, and IoT. However, the data in IoT are characterized by a large quantity, large capacity, and timely response, and existing blockchain systems only partially resolve them for data security and performance. We propose DSChain for IoT data security to address the challenges mentioned above. Our system uses a certificateless signature to ensure a trusted data source and public auditing to ensure the integrity of stored data while using ciphertext-policy attribute-based encryption to control access to shared data. Moreover, we propose a packaging mechanism based on the Merkle Hash Tree that effectively improves system performance. We implement the DSChain and provide a detailed analysis of performance and security. The experimental results indicate that DSChain can achieve approximately 1,035 transactions per second on a single peer and is scalable.

In edge-assisted cross-domain Industrial Internet of Things (IIoT), blockchain-based authentication is an effective way to build cross-domain trust and secure cross-domain data. However, existing authentication schemes still have serious challenges in terms of efficiency and security. In this paper, we propose a blockchain-based lightweight message authentication scheme. First, to address efficiency challenges, we build a blockchain-enabled edge-assisted lightweight authentication framework. This framework uses edge servers to assist smart devices in achieving cross-domain authentication and effectively reduce redundant interactions between entities. Second, to resolve the security challenges, we design a lightweight message authentication algorithm for cross-domain IIoT. The algorithm guarantees message security with low computational overhead and is suitable for multi-receiver cross-domain IIoT. The security proof and analysis demonstrate that the proposed scheme is secure under the random oracle model and can resist various attacks. The performance evaluation shows that our proposed scheme is superior in terms of computation and communication overhead when compared with other related schemes.

With the development of the industrial Internet of Things (IIoT), the amount of data generated by industrial manufacturing equipment will increase. To reduce the cost of data management while achieving secure data sharing, data owners generally upload the resulting ciphertexts to a cloud server after encrypting their data. Attribute-based encryption (ABE) is a valuable technology that implements fine-grained access control over shared information; however, its computational complexity is not suitable for resource-constrained IIoT devices, making it difficult to apply directly to an IIoT environment. To address this problem, we design a fine-grained data sharing scheme based on proxy re-encryption in IIoT. In the proposed scheme, data files are encrypted through an identity-based encryption and a data owner can authorize a semi-trusted proxy server to transform the ciphertext into an ABE ciphertext. This realizes fine-grained access control and decreases a data owner's computational cost in data sharing. In addition, the computational burden is outsourced to a cloud server, and users only need to perform simple computing operations. A formal security proof indicates the proposed scheme's selective chosen-plaintext attack security. Theoretical and experimental analyses illustrate that our construction is more efficient than previous schemes.

Dilithium is a signature scheme that is currently being standardized to the Module-Lattice-Based Digital Signature Standard by NIST. It is believed to be secure even against attacks from large-scale quantum computers based on lattice problems. The implementation efficiency is important for promoting the migration of current cryptography algorithms to post-quantum cryptography algorithms. In this article, we optimize the implementation of Dilithium with several new approaches proposed. Firstly, we improve the efficiency of parallel NTT implementations. The overhead of shuffling operations is reduced in our implementations, and fewer loading instructions are invoked for the precomputations. Then, we optimize the sampling and bit-packing of polynomial coefficients in Dilithium. We can handle double the number of coefficients within one register using a new approach for the sampling of secret key polynomials. The approaches proposed in this article are applicable to implementations under AVX2 and AVX-512 instruction sets. Take Dilithium2 as an illustration, our AVX2 implementation demonstrates improvements of 22.7%, 16.9%, and 13.5% for KeyGen, Sign, and Verify compared with the previous implementation.

With the popularity of the mobile Internet, data is increasingly becoming a new resource. Therefore, the trading of such data resources has become an increasing demand. In this paper, we propose a fair privacy-preserving data trading protocol based on blockchain. Firstly, our data trading protocol achieves fairness by carefully combining the probabilistic approaches and the fully homomorphic encryption techniques. Moreover, our protocol allows online arbitration when misbehavior occurs in the trading process is detected. Note that previous data trading protocols need a Trusted Third Party (TTP) or an offline arbitrator to solve disputes, weakening the trust of those protocols. Secondly, the data validity verification process of our protocol is more flexible. Most Importantly, different from all previous designs which only achieve privacy against communication channel eavesdroppers, our protocol achieves privacy against any eavesdropper and the passive arbitrator. The above-distinguishing properties of our protocol are mainly benefited from the homomorphic encryption and double encryption techniques. In addition, our data trading protocol can be instantiated with post-quantum primitives and thus achieves post-quantum security. To demonstrate the feasibility of the proposed protocol, we conduct a comprehensive evaluation with the instantiated cryptographic primitives based on the Ethereum test network.

Existing multitask outsourcing computations struggle to guarantee the fairness for participants and the correctness of the computation results. Some solutions use blockchain to address the fairness issue in outsourcing computations. However, blockchain suffers from poor data privacy due to its public and transparent nature, as well as the latency because of limited scalability. To effectively confront these problems, we propose the Libras: a fair, secure, verifiable and scalable outsourcing computation scheme based on blockchain. In Libras, tasks are divided into multiple sub-task blocks, coupled with a deposit mechanism that enforces fairness throughout the process. Libras integrates a commitment mechanism with on-chain and off-chain collaboration for security, where the computation results are securely stored off-chain while proofs of these results are immutably recorded on-chain. Moreover, it employs a Directed Acyclic Graph (DAG)-based ledger architecture to significantly expedite transaction confirmations and facilitate elastic scalability. Furthermore, we devise a batch verification algorithm to simultaneously verify the accuracy of all computation results. Theoretical analysis and experiments demonstrate that Libras is fair, secure, verifiable, and scalable. The comparison results indicate that the verification time is 1.2× that of FVP-EOC.

Vehicular Ad-hoc Networks (VANETs) constitute crucial elements within intelligent transportation systems. However, the rapid development of VANETs has brought forth an increasing number of security concerns. Conditional Privacy-Preserving Certificateless Signature (CPP-CLS) has emerged as a promising solution to ensure data security, preserve vehicle anonymity, and establish unlinkability in VANETs. In contrast to traditional public key infrastructure systems that involve cumbersome certificate management, and identity-based frameworks fraught with key escrow issues, CPP-CLS presents a more apt approach for VANETs. Unfortunately, the researches on CPP-CLS present a strange phenomenon in that a scheme proposed is always pointed out to have various security problems, especially public key replacement attacks. Moreover, there is a scarcity of published researches on the generic construction of CPP-CLS. To tackle these challenges, this paper proposes the first generic construction for CPP-CLS based on Type-T (Three-move type) signature, in which the public key reconstruction technique enables any receiver who owns a part of the sender’s public key and the KGC’s public key to reconstruct the complete sender’s public key, which can alleviate the public key replacement attacks. A formal security analysis proves that our scheme effectively guards against existential forgery under adaptively chosen message attacks in the random oracle model, contingent upon the security of the underlying Type-T signature. Furthermore, We provide two specific instantiations of the generic construction to verify feasibility. Among them, the instantiation based on module learning with errors is effective against quantum attacks. Based on extensive experimental results and theoretical analysis, our implementations surpass the majority of existing similar schemes in either performance or security. This substantiates the feasibility of our generic scheme, making it applicable for constructing CPP-CLS schemes.

Securing Internet of Vehicles (IoVs) systems against common threats such as false message injection remains challenging, and one typical approach is to deploy trust management solutions. In this work, we propose a Consensus-Adaptive Trust management (CAT) based on the Group Decision Making (GDM) in IoVs. Specifically, in our approach the consensus levels are calculated to measure the difference of opinions (trust values) among vehicles. To estimate the reliability of consensus levels, the divergence between consensus levels is calculated, namely: consensus level similarity. GDM allows us to dynamically adjust the opinion of vehicles (namely: Consensus Reaching Process, CRP). Then, a credit guarantee mechanism is designed to improve the efficiency of CRP and seek out malicious vehicles quickly. To empower the adaptability of trust management for changing environments in IoVs, CAT dynamically manages opinions of vehicles, self-confidence, and their consensus thresholds according to the feedback of delivered messages. Extensive simulation results show the potential of CAT operating in high-risk scenarios, and outperforming other competing baseline methods in terms of accuracy, precision, recall, and F-score.

In the Industrial Internet of Things (IIoT), blockchain-based data-sharing frameworks can effectively build cross-domain trust and facilitate data sharing. However, secure data-sharing schemes are lacking for the IIoT scenario, in which smart devices cannot communicate across domains and can only access data through edge servers. In this study, we propose a lightweight and secure data-sharing scheme for the blockchain-enabled cross-domain IIoT, in which authorized smart devices can access cross-domain data anonymously. First, smart devices can dynamically generate pseudonyms by themselves and without the online participation of domain authorization centers, effectively reducing the storage overhead of smart devices and the workload of domain authorization centers. Second, the scheme combines broadcast encryption and proxy re-encryption techniques, which realize flexible data sharing across domains while protecting the privacy of smart devices. Detailed security proofs and analyses demonstrate that the proposed scheme is secure and resistant to various attacks. The performance analysis shows that our proposed scheme is efficient and performs better than related schemes.

Payment Channel Networks (PCNs) are innovative second-layer scaling technologies that aim to improve transaction rates, reduce on-chain storage costs, and enable efficient atomic swaps for blockchain-based cryptocurrencies. Despite offering features like relationship anonymity, scriptless script, and cross-chain fairness, current PCNs encounter challenges in achieving identity anonymity and maintaining the fungibility of cryptocurrency units. PayMo, proposed in ESORICS’22, addresses payment anonymity but is limited to Monero, posing difficulties in extending it to a PCN framework. In response, this paper presents a novel Anonymity-Enhancing Multi-Hop Locks (AEMHL) mechanism for Monero-enabled PCNs. The AEMHL mechanism leverages our generic Linkable Ring Adaptor Signature (LRAS) construction and a minimalist PCN framework called anonymous multi-hop locks. This approach effectively combines privacy protection and simplicity while ensuring Monero’s fungibility without the need for specialized scripting support. Security properties, including atomicity, consistency, and anonymity-enhancement, are demonstrated using a universal composability model. Additionally, two optimized LRAS-based schemes are proposed to accommodate multi-hop locks construction in diverse scenarios. Through rigorous security analysis and performance evaluation, we confirm that AEMHL meets essential security objectives and provides efficient and practical solutions for privacy-conscious users within PCNs.

Threshold signatures as a method to realize multi-party cooperation and trust distribution in blockchain have been widely studied in recent years. However, among these researches, few threshold signature schemes achieve all the properties of accountability, privacy, and key protection for the EdDSA-based blockchain systems. To fill this gap, we propose an EdDSA-based accountable threshold signature protocol with privacy and proactive refresh, named TAPS-PR. Meanwhile, we define new security models and give a detailed analysis to prove protocol security. In TAPS-PR, the threshold is variable and hidden with the signing quorum from the public view. However, the signing quorum can be traced when threshold signatures related to fraudulent events are generated. We also enhance the key security of each signer by proactive refresh, which realizes updating the private key while the public key remains unchanged. Apart from that, we present ATS-PR with increased efficiency and reduced communication cost at the cost of weaker security. The theoretical analysis and experimental results indicate that our protocols perform efficiently in terms of communication and computation overhead. Furthermore, we use Tezos, a blockchain project employing EdDSA, as a case study to demonstrate the compatibility of our protocol with real-world blockchain applications.

Asynchronous common subset (ACS) is an essential building block for Byzantine fault-tolerance and multi-party computation. The classic ACS framework is due to Ben-Or, Kemler, and Rabin (BKR), consisting of${n}$reliable broadcast (RBC) instances and${n}$asynchronous binary agreement (ABA) instances (where${n}$is the total number of replicas). Despite recent progresses of practical BKR-ACS, the state-of-the-art designs are still trapped by a validity-latency tradeoff. In this paper, we propose Sweeper, a new ACS protocol that breaks the tradeoff, achieving optimal validity and latency. Moreover, Sweeper maintains other benefits including optimal resilience, signature-free, and information-theoretic settings. Sweeper is built on RBC and composable biased reproposable ABA (CBiased RABA). Different from the conventional RABA, CBiased RABA allows replicas to be more biased towards specific RABA instances. We provide generic strategies to transform existing ABA/RABA protocols and a new RABA protocol that we introduce, to CBiased RABA. Furthermore, Sweeper can achieve up to$2 \times $the throughput of PACE-ACS (CCS 2022), the state-of-the-art ACS protocol that follows the BKR-ACS framework.

The technology for securely sharing data has grown extensively in recent years. Many users are willing to share their lightweight mobile device data via social networks or the cloud. A novel matchmaking encryption primitive was proposed in CRYPTO’19, whose potential for privacy protection and data sharing security was introduced. However, matchmaking encryption technology faces challenges in flexibly realizing critical functions, such as one-to-many non-interactive scenarios, no key escrow problem, stronger security, lightweight computation and low communication overheads for mobile devices, which impede their widespread application. To achieve the above functions, we present a lightweight certificateless multi-user matchmaking encryption (LC-MUME) for mobile devices, which enhances security flexibly and performance based on standard hard assumptions and low-consumption pairing-free technology, while also avoiding one-by-one encryption for each user. The proposed LC-MUME scheme enjoys minor computation and communication overheads in a one-to-many non-interactive certificateless cryptosystem. We prove that our scheme achieves indistinguishability-based chosen-ciphertext attack (IND-CCA) security, the existential unforgeability under a chosen message attack (EU-CMA) security and anonymity-CCA security under the random oracle model. Our LC-MUME scheme outperforms the state-of-the-art schemes regarding efficiency and flexibility, as demonstrated by the performance comparison and analysis, and therefore is a practical solution for resource-constrained mobile devices.

The country’s governmental agencies bear the responsibility for overseeing and executing a wide range of national policies and initiatives, formulating pivotal determinations aimed at safeguarding national security and fostering long-term progress. Most of the decisions are highly confidential, encrypted and transmitted to diverse administrative regions, sectors, and individuals to facilitate execution. Hence, governmental agencies must formulate fine-grained access policies that support secure one-to-many document sharing. However, if the receivers’ keys were exposed, it could result in unauthorized access to document contents, posing a significant threat to national security. When facing keys exposure scenario, addressing the challenge of preventing document content theft while maintaining document archiving for convenient accountability becomes a complex and demanding task. To tackle the above issues, we propose an innovative lattice-based puncturable ciphertext-policy attribute-based encryption scheme. This scheme supports secure one-to-many document sharing, fine-grained access control, and empowers receivers to revoke the decryption capability for specific data according to their own choice after reviewing documents, thereby achieving dual-layer protection for documents. Our scheme has exhibited resilience against quantum attacks, chosen plaintext attacks and collusion attacks.

Generative Pretrained Transformer (GPT) is an advanced natural language processing (NLP) model and is excellent at understanding and generating human language. As GPT is increasingly utilized, more and more cloud inference services for pre-trained generative models are being offered. However, when users upload their data to cloud servers to experience cloud inference services, ensuring the privacy and security of their data becomes a challenge. Thus, in this work, we present SecureGPT, a framework for multi-party privacy-preserving transformer inference in GPT and design a series of building blocks which include M2A (conversion of multiplicative share to additive share), truncation, division, softmax and GELU protocols for our framework. Specifically, we follow the work of SecureNLP and further explore the M2A protocol for non-linear functions such as GELU and softmax. We also design multi-party private protocols for GPT’s transformer sub-layers. Finally we prove the security of our framework in the semi-honest adversary model with all-but-one corruptions. we evaluate the runtime of our framework under different parties settings and our implementation leads to up to$100\times $improvement compared to state-of-the-art works.

Recently, the concept of intelligent cyber-physical transportation systems (ICTS) has entered the vehicle network, providing more efficient, safe, and sustainable services by applying intelligent technology to the transportation system. Because the communication channel between the vehicle and the cloud service provider (CSP) is open and insecure. Therefore, we must construct a secure Vehicle-to-CSP (V2C) communication scheme to ensure the security of vehicle privacy data. Current communication schemes mainly have two limitations. One is that the user’s role in communication is not considered, and the other is that the computational and communication overhead are not sufficiently low to satisfy the low latency requirements. To address the deficiencies, we propose a user-centric V2C communication scheme. The primary key in the signature is concealed, which ensures the confidentiality of the user’s legal real identity. Its main steps, based on the extended Chebyshev chaotic map and hash function, reduce the computational and communication overhead in the process. The security proof and analysis show that our proposed scheme satisfies the security and privacy requirements. The performance analysis shows that our proposed scheme outperforms other related schemes.

Several authentication and key agreement (AKA) schemes have been proposed to ensure secure communication in the Industrial Internet of Things (IIoT). However, most of these schemes face two primary problems. First, they cannot resist various attacks, such as impersonation and device capture attacks. Second, these schemes overlook the resource-constrained IIoT devices, failing to guarantee lightweight overhead for device operations. Therefore, we propose a novel and efficient AKA scheme. Utilizing the chameleon hash function and physical unclonable function, the proposed scheme implements a lightweight overhead for both authentication parties while maintaining the overhead of the gateway within a reasonable range. Furthermore, we implement device anonymity based on lightweight operations such as hash and XOR. In addition, we perform a rigorous security analysis using the widely accepted Real-Or-Random model, BAN logic, and Proverif tool. Finally, through heuristic analysis and experiments, we substantiate that our scheme surpasses the compared schemes in terms of both security attributes and system overhead.

Nonlinear complexity is an important measure for assessing the randomness of sequences. In this paper we investigate how circular shifts affect the nonlinear complexities of finite-length binary sequences and then reveal a more explicit relation between nonlinear complexities of finite-length binary sequences and their corresponding periodic sequences. Based on the relation, we propose two algorithms that can generate all periodic binary sequences with any prescribed nonlinear complexity.

To enable the vehicle control system to provide better service, an increasing number of network nodes are being introduced into the vehicle; this also dramatically expands the attack surface of modern vehicles. In recent years, the security of vehicle communication buses and electronic control units (ECUs) has been extensively studied. However, in actual deployment, there is little concern for the fine management of secure communication schemes with respect to the security level of the ECU on the controller area network (CAN). On this basis, this paper proposes a two-layer ECU group dynamic management scheme based on the Chinese remainder theorem. Dynamic grouping management based on the credibility of ECUs while the vehicle is running can effectively balance efficiency and security. During communication, different groups use different modes to achieve higher efficiency. Security analysis shows that the proposed scheme can satisfy the requirements of security and privacy. Simulation results further demonstrate that the proposed scheme performs well in terms of computing and communication costs.

Advances in machine learning have enabled a broad range of complex applications, such as image recognition, recommendation system and machine translation. Data plays an important role in our increasingly complex and diverse environments, and this also reinforces the importance of data privacy in machine learning-enabled applications. Although there are a number of literature survey articles on machine learning, only a few studies have investigated the cryptographic primitives used in privacy-preserving machine learning (PPML). In other words, there is no, or limited, systematization of knowledge (SoK) that provides a comprehensive introduction to cryptography that have been deployed in PPML. In this paper, we firstly introduce some basic concepts such as machine learning tasks and processes. Then, we review and systematize the cryptographic primitives used in PPML. We analyze these existing privacy-preserving schemes in their learning process, especially training and inference. Finally, we conclude our survey and provide an outlook on future trends and research directions in the field.

Vehicular Ad hoc Networks (VANETs) are vulnerable to various types of attacks. Intrusion Detection System (IDS) based on machine learning can effectively detect malicious network attacks in VANETs. However, machine learning training necessitates ample data which contain significant ample private information, increasing the risk of privacy disclosure. The privacy protection of training data for machine learning used in the IDS of VANETs is rarely investigated. Meanwhile, Differential Privacy (DP) is one of the most secure privacy protection methods based on perturbations. Therefore, we propose a lightweight hybrid IDS (LH-IDS) based on machine learning and DP. It uses algorithms based on unsupervised learning to detect anomalous network behaviour with high performance, especially unknown attacks in VANETs, while protecting data privacy. The DP is used to secure the privacy of the training data. Noise from different privacy budgets is added to datasets to obtain DP datasets. Subsequently, LH-IDS is used to verify the utility of the DP datasets. Extensive experiments confirm LH-IDS can not only detect anomalous and normal traffic with excellent performance but can also protect the private information of the training data. Additionally, the proposed model incurs only minimal CPU and memory overhead, making it a lightweight solution.

Data sharing is one of the essential services of vehicular ad hoc networks (VANETs), which primarily requires data security and access control, and ciphertext-policy attribute-based encryption (CP-ABE) is a promising tool. However, data sharing schemes of distributed CP-ABE have concerns about the single-point performance bottleneck and privacy leakage. The factor for the former is that the authority manages a disjoint attribute set. The latter is because the user's identity and attributes are required to submit to authorities, which targets to bind this information to decryption keys for collusion-resistant. We propose a privacy-preserving distributed data sharing scheme for VANETs. This scheme introduces asymmetric group key agreement to distributed CP-ABE, which realizes that multiple authorities manage an attribute, and the user can obtain the attribute key bound with his identity from any authority in the group. To match up to the requirement of privacy-preserving, a key extract protocol provided user anonymity is proposed, which implements that attribute keys can be obtained without revealing the user's identity and attributes. Moreover, partial policy hiding is satisfied. Finally, we analyze and evaluate the proposed scheme, and the results indicate that our scheme is secure and efficient.

Since the communication channels in vehicular ad-hoc networks (VANETs) are wireless and open, malicious adversaries can monitor or fabricate messages transmitted across them. To secure vehicular communications, an authenticated key agreement (AKA) scheme needs to be designed for VNAETs. Traditional VANETs AKA schemes require the trusted authority (TA) to authenticate the legality of message and corresponding sender. However, the TA in these schemes is vulnerable to suffer from single-point-of-failure issues. Some blockchain-based VANETs AKA schemes have been proposed recently to address the deficiency. However, these schemes rely on the consortium or private blockchain in which TAs are still required for key generation, resulting that the practicality is limited. To solve the issue, we design a smart contract-based VANETs AKA scheme, where the AKA algorithm of our proposed scheme is implemented on smart contract deployed on a public blockchain system and the TA that is responsible for key generation will not be required. The security proof and analysis show that our proposed scheme satisfies the session-key semantic security and essential security and privacy requirements, respectively. The performance analysis demonstrates that our proposed scheme outperforms existing blockchain-based VANETs AKA schemes.

The authentication and key agreement (AKA) scheme for VANETs can produce a series of short-term session keys, which can be used to secure the vehicular communications across open and insecure wireless channels. Traditional VANETs AKA schemes tend to employ the centralized trust architecture as the core authentication backend, which raises concerns about system security and reliability. Recently, several VANETs AKA schemes that are constructed on decentralized trust architecture have been proposed. However, these schemes do not achieve full decentralization and tend to suffer from key exposure issues, insufficient performance, and lack of optimization for on-chain storage costs. To address these shortcomings, we propose a threshold-based full-decentralized VANETs AKA scheme that is powered by consortium blockchain. In our proposed scheme, the threshold-based voting concept is employed to mitigate the key exposure issue inherent to the network infrastructure. Furthermore, we leverage lightweight cryptography in conjunction with the Cuckoo filter to reduce computational, communication, and on-chain operation costs brought by cryptographic operations and smart contracts. The security proof together with the cryptographic protocol validation tool prove the security of our proposed scheme, whereas the simulation experiment demonstrates the efficiency of our proposed scheme.

Vehicular ad hoc networks (VANETs) establish wireless connections among all vehicles, enabling seamless mobile communication. However, existing conditional privacy protection VANETs authentication schemes fail to address the issue of potential key-exposure and do not provide accelerated vehicle authentication. In this paper, we propose a reputation incentive committee-based secure conditional dual authentication scheme for VANETs called RIC-SDA. Our proposed scheme incorporates dual authentication of the consensus committee and vehicle-to-vehicle (V2V) communication. It enables the rapid provision of dynamic vehicle epoch-key from consensus committee authentication for V2V authentication through our designed reputation incentive mechanism. To mitigate the potential key-exposure problem, we introduce a novel concept of secure vehicle epoch communication, which means V2V authentication is valid for only one epoch blockchain unit time. The proposed scheme achieves lightweight computation and incurs minimal communication overheads, with the signature size being just 137 bytes. The RIC-SDA scheme supports fast batch verification. We prove that our proposed scheme is unforgeable security under random oracle and demonstrate its feasibility by implementing it in a test network based on Ethereum Sepolia. The results demonstrate that our RIC-SDA solution outperforms the existing state-of-the-art authentication VANET schemes regarding efficiency and communication costs.

Vehicular ad hoc networks (VANETs) connect all vehicles through wireless channels. They provide extensive real-time traffic information services that improve driving safety and traffic management efficiency. However, VANETs are vulnerable to security attacks because of the open wireless nature of their communication channels. Most security mechanisms for traditional VANETs are centralized and have certain limitations in satisfying security requirements, such as anti-single-point failure, distributed security authentication of messages, and privacy preservation in VANETs. To address these issues, herein, we propose a dual blockchain-assisted conditional privacy-preserving authentication framework and protocol for VANETs. The identity authentication and privacy preservation of vehicles in VANETs can be realized without relying on a centralized trusted third party. The proposed scheme also allows for the conditional tracking of illegal vehicles. The decentralized dynamic revocation of illegal vehicles can be realized through smart contracts, rendering the scheme efficient and scalable. We implement this scheme in an Ethereum test network to demonstrate its feasibility and conduct an in-depth security analysis and comprehensive performance evaluation of the proposed scheme. The results demonstrate that the proposed scheme is an effective solution for the development of a decentralized authentication system for VANETs.

In vehicular networks, caching content on an edge server (ES) is a popular method for quickly responding to massive vehicle service requests, reducing communication delays, and enhancing driver and passenger service experiences. However, after integrating ESs with vehicular networks to provide vehicles access to the cached content in these ESs, significant challenges regarding protecting the privacy of vehicle data and communication security arise. In this study, to address security and privacy-preserving issues, we propose a secure and revocable cache-based distributed data sharing scheme for vehicular networks wherein a token authentication mechanism and multi-authority ciphertext-policy attribute-based encryption are integrated. In this scheme, both authentication and authorization capabilities are delegated to an ES while restricting access to service content to only legal vehicles, achieving proper access control between vehicles and ESs, and effectively preserving the privacy of vehicle data. Moreover, we attributed the revocations of ESs to the associated attribute authorities, eliminating the need for a system-wide update of keying materials. Through rigorous security proofs and detailed security analyses, we demonstrate that the scheme meets the security requirements of vehicular networks and can resist more security attacks. The proposed scheme achieves better balance between computational and communication costs than related schemes.

A verifiable timed signature (VTS) scheme allows a signature to be time-locked to a known message for a predetermined duration denoted as$\mathsf {T}$. Verifiability ensures that anyone can verify that the time-lock contains a valid signature without completing the computation. In this paper, we introduce a novel VTS construction method based on the RSA group, designed to maintain a constant level of size. This approach serves as an improvement over the previous linear level size construction method (CCS 2020). First, we construct it by using a commitment to a valid RSA signature. This commitment can only be opened to a regular RSA signature after a sequential computation period. Our scheme utilizes a trapdoor verifiable delay function, RSA signatures, and a specialized zero-knowledge proof to instantiate the proposed scheme. We also conduct proofs in three aspects: correctness, soundness, and security. Furthermore, we identify potential applications for VTS and present a simple Bitcoin voting protocol based on an open vote protocol by utilizing VTS. Experimental results show that our scheme is more efficient compared to the construction of VTS (CCS 2020), reducing the signature size by at least 90.5% and lowering computational costs by at least 77%.

With the rapid development of 5 G and 6 G technologies, vast amounts of data are being generated. To save costs and ensure data security, these data are typically uploaded to multiple cloud servers. For handling massive data, distributed storage is necessary. Additionally, remote data integrity checking is essential. To achieve this, the PDP paradigm (Provable Data Possession) has been proposed. Unfortunately, existing PDP schemes suffer from inefficiencies. The main cause is that the data must be divided into small blocks with a limited size, such as 160 bits for bilinear pairings-based PDP schemes. This approach incurs significant computation and communication costs.To address this issue, we propose a new model called synchronous blockchain-based DPDP (Distributed Provable Data Possession) with forward-security in multi-cloud storage. This new concept leverages blockchain, which is the foundation of cryptocurrency. The paper formalizes the system model and security model for the new concept. Furthermore, a concrete blockchain-based DPDP scheme is designed using blockchain and RSA. The proposed scheme is provably secure, and its performance is analyzed from both theoretical and implementation perspectives. Our analysis demonstrates that the proposed DPDP scheme is provably secure, synchronous, forward-secure, efficient, and practical.

Matchmaking encryption is a method employed to address the security and privacy concerns of cloud-enabled IoT healthcare. Nevertheless, matchmaking encryption technology encounters challenges in effectively implementing critical functionalities, such as resolving a single-key-exposure problem, achieving secure short-epoch communication, and simultaneously enabling lightweight computation and communication overheads for IoT healthcare. These challenges pose obstacles to the widespread adoption of this technology. To tackle these constraints, we first present aReputation incentive committeeConsensus-based forMatchmakingEncryption in IoT healthcare (RCME), which utilizes consensus nodes to eliminate the single-key-exposure problem and enables fast provision of permission proof based on our design reputation incentive mechanism. The proposed RCME scheme adopts low-consumption pairing-free technology to realize lightweight matchmaking encryption in a multi-party, non-interactive certificateless cryptosystem. Rigorous security analysis shows it achieves chosen ciphertext attack security under the random oracle model. To further reduce consensus communication overhead from$\mathcal {O}(n^{2})$to$\mathcal {O}(n)$, we propose an optimized Practical Byzantine Fault Tolerance (PBFT) consensus, and we adopt reputation incentive mechanism and threshold cryptography technology to achieve unbiased leader election. The comprehensive evaluation corroborates that our solutions outperform the existing state-of-the-art schemes regarding security and performance. Therefore, our RCME scheme is a practical solution for resource-constrained IoT healthcare devices.

Federated Learning (FL), as a distributed machine learning technique, has promise for training models with distributed data in Artificial Intelligence of Things (AIoT). However, FL is vulnerable to Byzantine attacks from diverse participants. While numerous Byzantine-robust FL solutions have been proposed, most of them involve deploying defenses at either the aggregation server or the participant level, significantly impacting the original FL process. Moreover, it will bring extra computational burden to the server or the participant, which is especially unsuitable for the resource-constrained AIoT domain. To resolve the aforementioned concerns, we propose FL-Auditor, a Byzantine-robust FL approach based on public auditing. Its core idea is to use a Third-Party Auditor (TPA) to audit samples from the FL training process, analyzing the trustworthiness of different participants, thereby helping FL obtain a more robust global model. In addition, we also design a lazy update mechanism to reduce the negative impact of sampling audit on the performance of the global model. Extensive experiments have demonstrated the effectiveness of our FL-Auditor in terms of accuracy, robustness against attacks, and flexibility. In particular, compared to the existing method, our FL-Auditor significantly reduces the computation time on the aggregation server by 8×-17×.

Convolutional neural network (CNN) has attracted increasing attention and been widely used in imaging processing, bioinformatics and so on. As the cloud computing and multiparty computing are booming, the training and inference data of convolutional neural network often comes from diverse users. These users tend to jointly perform the computation but reluctantly share original data with others. Multi-key fully homomorphic encryption (MKFHE) supports homomorphic computation on ciphertexts encrypted with different keys, which is especially suitable for this scenario. In this paper, we firstly propose secure convolution, matrix multiplication, comparison and maximum protocols based on MKFHE. Then we design the secure CNN training and inference framework, outsourcing almost all computations to cloud server. To improve the efficiency, we use key switching technique for ciphertext transformation. We prove that the proposed frameworks are secure and feasible. The theoretical and experimental analysis show that our framework achieves the trade-off between security, efficiency and scalability.

The mobile healthcare (mHealth) is a promising and fascinating paradigm, which can dramatically improve the quality of healthcare delivery by providing remote diagnosis and medical record sharing. Now, the mHealth faces serious challenges such as data leakage and unauthorised access currently. Attribute-based encryption (ABE) which has been employed for mHealth is an excellent cryptographic primitive of securing data sharing. However, there are still some security and efficiency issues in the ABE-based data sharing scheme for mHealth. Firstly, the explicit storage of access policy may expose the privacy of users. Secondly, the computation cost is high, especially in the mHealth with IoT devices. Thirdly, the authentication of access rights to shared data is usually performed by the centralised third parties or IoT devices with limited resources. To handle the above issues, this paper presents a privacy-preserving and efficient data sharing scheme. The scheme partially hides access policy to protect user's privacy, and introduces an offline mechanism in key generation and encryption phase to improve efficiency of mHealth. Furthermore, it also provides decentralised and trusted authentication of data access right based on blockchain. The security proofs and the experiment results demonstrate that the presented scheme has better security and efficiency.

The Multi-receiver Encryption (MRE) scheme can meet the secure data transmission requirements in multicast and broadcast scenarios. To meet compliance, critical information infrastructure in China should be protected with Chinese national commercial cryptographic algorithms. Designing an MRE scheme based on Elliptic Curve Cryptography (ECC) is one of the current design methods with better flexibility and performance. However, the research on MRE schemes based on SM2 elliptic curve public-key cryptography is still in a blank state. This paper proposes a Certificateless SM2-based Multi-receiver Encryption (CL-SM2-MRE) scheme. We prove the security of the CL-SM2-MRE scheme under the Random Oracle Model (ROM) and analyze the performance.

Recently, with the rapid improvement of e-health technology, a large amount of precious medical data has been accumulated in different entities, such as hospitals, clinics, and medical institutions, promoting the development of data sharing in e-health services. However, most of them lacks fine-grained functionalities: selective linkability and traceability, which are critical in an e-health environment. Furthermore, we observe that existing schemes mostly rely on centralized storage centers, which will lead to a single point of failure and privacy disclosure. In this article, we first construct a group signature schemeSLTGSsuitable for a data sharing environment. It supports selectively linking two different message-signature pairs to the same signer. Further, it provides an algorithm to trace the signer. Then, based on theSLTGSscheme, we leverage distributed technology (i.e., interplanetary file system (IPFS) and blockchain) and attribute-based encryption to propose a distributed data sharing scheme. We claim that our scheme meets anonymity, accountability, linkability, traceability, fine-grained and efficient access control, and distributed storage. Moreover, the proposed data sharing scheme yields a practical performance making it suitable for e-health applications.

The Internet of Medical Things (IoMT), which integrates medical sensors with the Internet of Things, is helpful for providing remote diagnosis and real-time decision making. Massive data collected by medical and healthcare monitoring sensors in the IoMT involves sensitive patient information. It brings some security challenges to validate the legitimacy of participating entities and protect patient data privacy. A certificateless signcryption (CLSC) scheme combines encryption and signature that can offer authenticity, confidentiality, and unforgeability, providing a viable solution to the data privacy issue of the IoMT. However, existing CLSC schemes fail to meet confidentiality or unforgeability, or require expensive computation overhead to perform pairing operations. This article first presents a new CLSC scheme for secure data transmission and better smart services in IoMT, which replaces the signature part with the Schnorr signature. We then give a thorough security proof under the random oracle model. Besides, we elaborately evaluate the performance and security of some existing solutions with our solution. Finally, the experiment results indicate that our solution can achieve a better balance between security and performance than some existing schemes. Therefore, in terms of feasibility, our scheme is more suitable for the IoMT scenario.

The Industrial Internet of Things (IIoT) incorporates massive physical devices to collect ambient data. Due to the limited types of equipment in IIoT, most of the data has to be saved on a cloud server before it can be processed and analyzed. The ciphertext generated by traditional encryption techniques is difficult to search in subsequent use. Public-key encryption with keyword search (PEKS) can provide data encryption as well as confidential searching, but traditional PEKS schemes are susceptible to internal keyword guessing attacks (IKGAs) caused by the limited space of commonly used keywords. To address this issue, the cryptographic primitive of public-key authenticated encryption with keyword search (PAEKS) was proposed, while most of the existing schemes are not appropriately applied to IIoT for involving time-consuming bilinear pairing operations. In this article, we first propose a user-friendly PAEKS scheme that totally circumvents bilinear pairing operations during generating keyword ciphertext and trapdoor. Then, we prove its multiciphertext indistinguishability (MCI) and trapdoor privacy based on decisional$q$-ABDHE and computational Diffie–Hellman assumptions in the random oracle model together with conducting the theoretical and experimental comparisons. The results show that the computational overhead of our proposal is significantly reduced comparing with most existing classical PAEKS schemes without causing other communication costs or security loss. Due to its better performance and security, our scheme is better suited for lightweight devices in the IIoT.

The Industrial Internet of Things (IIoT) and cloud computing have developed rapidly in recent years. Many enterprises are willing to outsource lightweight devices’ industrial data via the cloud to lower manufacturing costs and enhance production efficiency. The data sharers, however, usually have concerns about the security and privacy of their data stored in cloud outsourcing systems. Traditional certificateless searchable encryption primitives are tough to realize dynamically revocable and high-efficiency decryption. Furthermore, data sharing on untrusted devices may cause a single-key exposure problem. To address these issues, we propose a blockchain-assisted secure data-sharing protocol with a dynamic multiuser keyword search (DMUKS) in IIoT, which utilizes blockchain-assisted techniques to solve a single-key exposure problem and to realize fast certificateless keyword search as well as dynamic user and key management. The proposed DMUKS scheme enjoys minor computation and communication overheads. It maintains a constant ciphertext and trapdoor query size as users increase and supports user addition and revocation. Moreover, it periodically supports key and ciphertext updating and is secure against keyword-guessing attacks under the random oracle model. The performance comparison and analysis demonstrate that it is more efficient and flexible than the existing data sharing with keyword search schemes.

An edge-cloud Industrial Internet of Things (IIoT) can help meet the computing requirements of industrial applications, particularly in time and latency-sensitive services. Ensuring the security and privacy of (sensitive) information collected by IIoT end devices is crucial, and has an important impact on the decision making as well as operational safety. However, these devices are energy constrained and vulnerable to corruption. The authentication schemes suitable for this environment need to be lightweight, efficient, and concise. In this article, we propose a symmetric-key authentication scheme with a perfect forward secrecy (SAPFS), which relies on both authentication and derivation master keys. The SAPFS scheme uses only XOR operation and hash function to achieve mutual authentication, key exchange, and message integrity. On the condition of the irreversible hash function and indistinguishable master keys, we demonstrate that SAPFS is provably secure under the random oracle model. Finally, a comparative summary with three other competing schemes (in terms of communication cost, storage requirement, and computation complexity) demonstrates its utility.

The prosperity of blockchain has pushed various decentralized applications, e.g., cross-regional finance, due to its advantages of openness, immutability, and decentralization. The feature of openness inevitably leads to a serious privacy breach. Recently, various privacy-enhanced works (e.g., Zcash, Monero) were proposed focusing on this problem. However, most existing solutions either aim for the unspent transaction output (UTXO) model, or fail to provide full privacy protection for the account-based model with efficient performance. In this paper, we put forwardLedgerMaze, an efficient privacy-preserving non-interactive zero-knowledge (NIZK) scheme over account-model blockchain. We design a novel scheme calledchequemechanism to cut the link between the sender/receiver relationship. Namely, a sender transfers money to a receiver's cheque, then the receiver can retrieve the cheque among a set of cheques for obfuscation without revealing the original one. We construct several efficient NIZK proofs for initializing the mechanism. Moreover, we further analyze the security properties ofLedgerMaze. Experimental results show thatLedgerMazeachieves comparable performance in communication and computation costs while retaining a full privacy guarantee, compared to previous similar constructions.

In crowdsensing, we can leverage intelligent devices and real-time incentive mechanisms to facilitate the collection of reliable and timely data in Industrial Internet of Things (IIoT) settings. In such a setting, one can use cryptographic primitives to support data privacy preservation and quality-aware reward distribution simultaneously. However, existing approaches might incur expensive computation costs, suffer from overflow problems, or rely on implicit security conditions. In this paper, we propose anEfficient andPrivacy-preservingReal-timeIncentive system forCrowdsEnsing (EPRICE), designed to estimate the reliability of sensing data in a privacy-preserving setting. The theoretical analysis demonstrates that our proposed system achieves a high level of privacy-preserving for real-time reward distribution and supports practical privacy-preserving properties. The experimental findings show that our proposed EPRICE system significantly decreases the computation costs bythree orders of magnitudecompared with other competing schemes.

By introducing collision information into divide-and-conquer distinguishers, the existing collision-optimized side-channel attacks transform the given candidate space into a significantly smaller collision space, thus achieving more efficient key recovery. However, the candidates of the first several subkeys shared by collision chains are still repeatedly detected, which happens very frequently and brings huge computational overhead. To alleviate this, we propose a highly efficient collision-optimized attack named collision tree (CoTree). This collision detection tool exploits tree structure to store the chains created from the same subchain on the same branch, thus significantly reducing the storage requirements. It then benefits from the properties of both tree and collisions and exploits a top-down tree building procedure and traverses each node only once when detecting their collisions with a candidate of the subkey currently under consideration. Finally, unlike the traditional top-down node removal, CoTree launches a bottom-up branch removal procedure to remove the chains unsatisfying the collision conditions from the tree after traversing all the considered candidates of this subkey, thus avoiding the traversal of the branches satisfying the collision condition. These strategies make our CoTree significantly alleviate the repetitive collision detection, and our experiments verify that it significantly outperforms the existing works.

Identity-based encryption with equality test (IBEET) provides a feasible way for cloud server partitioning or searching on ciphertexts in the cloud. In that case, the server can judge if two different ciphertexts encrypt the same plaintexts or not. In response to threats posed by quantum computers, lattice-based IBEET schemes have been proposed to make cloud service post-quantum secure. However, those schemes are inefficient and can hardly meet the needs of resource-constrained devices. In this article, an efficient post-quantum IBEET scheme is introduced, which achieves testability by embedding the hash value of plaintext into testing trapdoor instead of encrypting it directly and doubling the size of ciphertext. We also prove that, with the Learning With Errors (LWE) problem assumption, the new scheme is one-way secure against selective identity and chosen ciphertext attacks (OW-sID-CCA) in quantum secure model. Furthermore, we evaluate the performance of the new construction and demonstrate its efficiency by showing that it only costs about half storage comparing with other lattice-based IBEET schemes. The execution time of encryption and decryption phrases in the new scheme reduce by 50%, while the computational cost in test algorithm keeps the same. Therefore, the new proposed IBEET is much more practical for working in post-quantum cloud computing scenarios.

Vehicular Ad-hoc Networks (VANETs) are with great potentials to facilitate traffic management and improve driver safety. Blockchain-based conditional privacy-preserving authentication (BCPPA) is proposed to achieve an optimal tradeoff among anonymity, traceability and key/certificate management in VANETs. Existing BCPPA protocols mitigate these security and privacy challenges by adding a significant cost on verification and traceability. As a result, current solutions fail to meet high mobility, low latency, and real-time requirements of VANETs. In this paper, we design three new system building blocks namely key derivation (KeyDer), signatures of knowledge (SoK) and smart contract, following by a more efficient BCPPA protocol (named as EBCPA). To show the advantage of EBCPA, we first demonstrate it can satisfy the necessary requirements (e.g. message authentication, conditional privacy protection, resilience to common attacks, and so forth). Moreover, we implement the EBCPA in the on-line Ethereum test network (Rinkeby), Hyperledger test network and VANETs simulation environment (via VanetMobiSim and NS-2). Finally, we evaluate its communication overhead and computational cost via comparing to existing BCPPA protocols that strive to achieve similar properties. From the implementation and comparison results, our proposal can improve efficiency by reducing the time cost of traceability at least 48.95% and verification at least 42.21%.

The rapid development and wide application of blockchain not only highlight the significance of privacy protection (including anonymity and confidentiality) but also the necessity of auditability. While several ingenious schemes such as MiniLedger and traceable Monero supporting both privacy protection and auditability have been proposed, they either provide incomplete privacy protection (only achieving anonymity within a small set or only providing confidentiality but not anonymity), or involve additional auditing conditions such as reaching threshold transaction volume or requiring permissioned nodes to serve as the manager, or restrict to specific blockchain types such as Monero. To mitigate these issues, this article proposes a generic anonymous, confidential, and auditable transaction system (named ACA), which is compatible with both UTXO-based permissionless and permissioned blockchains. Core technologies of ACA include designed traceable anonymous key generation and publicly verifiable authorization mechanisms from existing cryptographic tools (i.e., public key encryption, partially homomorphic encryption, and accumulator) as well as the meticulous designed signatures of knowledge and smart contract. To demonstrate the entity of our proposal, we first prove its security including authenticity, anonymity, confidentiality and soundness, and then provide an instantiation to evaluate its performance. The final implementation and benchmarks show that our proposal can still gain performance advantage even adding more functionalities.

Smart-card based password authentication has been the most widely used two-factor authentication (2FA) mechanism for security-critical applications (e.g., e-Health, smart grid and e-Commerce) in the past decades, and it is likely to hold its status in the foreseeable future. Hundreds of this type of 2FA schemes have been proposed, yet to our knowledge, most of them are built on the intractability of conventional hard problems (e.g., discrete logarithm problems and integer factoring problems) which are no longer hard in the quantum era. With the recent advancements in quantum computing, the design of secure and efficient smart-card based password authentication schemes against quantum attacks is becoming increasingly urgent. However, it is not as simple as it seems,how to design such a quantum-resistant 2FA scheme is challenging due to the demanding security requirements and the resource-constrained nature of mobile devices. In this work, we take the first step towards this issue by proposing Quantum2FA, a practical quantum-resistant smart-card-based password authentication scheme that employs Alkimet al.’s lattice-based key exchange and Wang-Wang’s “fuzzy-verifier + honeywords” technique (IEEE TDSC’18). Particularly, Quantum2FA can thwart the newly revealed key-reuse attack (ACISP’18, CT-RSA’19) against lattice-based key exchange schemes in two aspects: signal leakage attacks and key mismatch attacks. Specifically, it restricts the necessary conditions (i.e., the attacker must be the initiator of the key exchange) for an adversary to analyze the signal; It introduces honeywords to detect the key mismatches between the smart card and the server, and thus smart card loss attack can be thwarted. We formally prove the security of Quantum2FA under the random oracle model and demonstrate its efficiency through experiments on a 32 MHz 8-bit AVR Embedded Processor. Comparison results show that Quantum2FA is not only more secure but also offers better computation efficiency than the state-of-the-art conventional 2FA schemes.

In response to the threat posed by quantum computers, Pilaram and Eghlidos proposed the first lattice-based multi-stage secret sharing scheme which is the only post-quantum multi-stage secret sharing scheme. In this paper, we introduce an efficient attack on it and show that any adversary can easily reconstruct unrecovered secrets as long as it collects enough pseudo-secret shares. For the sake of complete, we further list two countermeasures to protect the scheme from such attack.

Identity-based cryptography is proposed to solve the complicated certificate management of traditional public-key cryptography. The pairing computation and high-level tower extension field arithmetic turn out to be the performance bottleneck of pairing-based signature schemes. Graphics processing units have been increasingly popular for general-purpose computing in recent years. They have shown a lot of promise in speeding up cryptographic schemes such as AES, RSA, and ECDSA. However, to our knowledge, the research on parallel implementation of pairings and identity-based cryptographic schemes on graphics processing units is somewhat outdated. Therefore, in this article, we implement the identity-based signature scheme in the IEEE P1363 Standard on a modern NVIDIA RTX 3060 card. We convert the pairing computation in signature verification into a product of pairings with fixed arguments and therefore avoid the scalar multiplication in 𝔾 2 . Then we employ the precomputation technique to improve the elliptic curve scalar multiplication, exponentiation in \(\mathbb {F}_{p^{12}}\) and the pairing computation. We also apply PTX ISA to multiple-precision arithmetic. Experiments demonstrate that our implementation can perform 43,856/46,753/39,798 pairings/sec for the Optimal Ate pairing, the pairing with a fixed argument, and two pairings with fixed arguments, respectively. Peak throughputs of signature generation and verification can achieve 322.6 and 40.6 kops/sec over the BN254 curve.

With the development of quantum computing, the existing cryptography schemes based on classical cryptographic primitives will no longer be secure. Hence, cryptographers are designing post-quantum cryptographic (PQC) schemes, and ideal lattice-based cryptography has emerged as a prime candidate. Today, as ideal lattice-based cryptography becomes more mature, its performance becomes an important optimization goal. In ideal lattice-based cryptography, polynomial arithmetic and polynomial sampling are the most time-consuming operations and therefore need to be accelerated. In this article, taking advantage of the parallelism of new 512-bit advanced vector instructions (AVX512), we present parallel implementations of polynomial arithmetic and polynomial sampling, thus comprehensively improving their performance. We conduct experiments with the Dilithium scheme(one scheme of NIST PQC Standardization Process Round-4). Our implementation gets a nice performance boost compared to its pure C language and 256-bit advanced vector instructions (AVX2) implementation.

Cloud-assisted electronic health records (EHRs) provide convenient medical services for patients by storing and analyzing medical data records in the cloud, but searching for sensitive data (e.g., identity, medical history) in the cloud conflicts with privacy protection requirements. Searchable encryption (SE) is a good cryptographic primitive for solving this conflict, which allows the user to store their encrypted data in the cloud and search them later in encrypted domain. However, the direct applications of most existing SE schemes in cloud-assisted EHRs may result in challenges, for example in terms of functionality, security and efficiency. In this paper, we propose BPVSE, a new verifiable and dynamic SE scheme for cloud-assisted EHR. BPVSE has the following advantages over existing approaches. First, leveraging blockchain and hash-proof chain, BPVSE allows the user to publicly verify the search result returned by the cloud without a trusted authority. Second, BPVSE supports dynamic datasets with forward and backward security, using our newly designed new hidden data structure. Third, BPVSE enables the user to launch parallel search with efficient encryption. We formally prove the security of the proposed BPVSE, and also conduct theoretical comparison and experimental evaluation to show its superiority of functionality, security, and efficiency.

The security of secret keys for blockchain-based applications is increasingly important, partly because the theft of secret keys will render a significant financial loss. To guarantee the security of secret keys, many multi-party signature protocols have been proposed. However, few of them are designed for EdDSA-based blockchain that is developing in growth. The folklore and the NIST document for standardizing threshold schemes believe that a distributed hash evaluation is required to design multi-party EdDSA protocols, which leads to a relatively large overhead. In this paper, we present two practical multi-party EdDSA protocols for semi-honest and malicious settings. Our protocols eliminate the distributed hashing by securely maintaining a global state, which is feasible for EdDSA-based blockchain. Furthermore, we extend the malicious protocol to resist DoS attacks by identifying corrupted parties in case of execution aborts. We implemented our EdDSA protocols for different parties using Alibaba cloud servers with all instances of type ecs.t5-c1m2.large. Our protocol in the malicious setting takes 1.51-15.3 ms between 2 parties and 5 parties, and are two orders of magnitude faster than the recent threshold EdDSA protocol. These properties (efficient, identifiable abort, high compatibility) make the two protocols ideal for threshold wallets for EdDSA-based cryptocurrency.

Aggregate signatures enable the sensor nodes of Industrial Internet of Things to send their signatures to the aggregator to realize signature compression. Before being stored in the data center, sensitive data and non-sensitive data should adopt different data processing methods in the process of sensor data fusion. In the high security analysis scenario of Industrial Internet of Things, only the verifier with a specified high security level can verify the resulting aggregate signature. So far, no one has explored how to ensure sensitive data privacy in the designated-verifier aggregate signatures. Motivated by it, this paper proposes a designated-verifier aggregate signature scheme (named DVAS) based on permissioned blockchain to achieve sensitive data privacy. In this scheme, the aggregator can be used not only to aggregate signatures, but also to sanitize data. Through smart contracts, the aggregator can sanitize the sensitive data according to the contract, and convert the original signature of the sensitive data into a valid signature. Therefore, DVAS can achieve elastic sensitive data privacy, not limited to encryption operations. The security attributes of DVAS include conditional anonymity, unforgeability, immutability and protecting data privacy. At the same time, DVAS realizes accountability through signature verification. Finally, the formal security proof, performance evaluation and experiments indicate that DVAS is secure, effective and practical for Industrial Internet of Things.

The anonymous credential has broad-ranging applications, for example for the pay-as-you-go strategy in the electronic subscription. However, the ‘plain vanilla’ pay-as-you-go strategy may not be suitable for non-regular users since the latter group is likely to require a tighter identity supervision mechanism. We also note that a key building block in the construction of an anonymous credential system is identity supervision. Since identity supervision is more than revocation, the approach to regulating user behavior needs to be both reasonable and practical. In a situation where the user is allowed to control their own identities, the latter approach could be more flexible compared to the revocation. There are existing works about the limitation on the k-times or epochs. However, due to the weaknesses of these single limitations, the combination of the customized k-times and epochs is necessary and remains to be done. In this paper, we present a permissioned redactable credentials scheme, which allows fine-grained supervision, user control, and user redaction. In our approach, we choose times and epochs as the regulation dimensions, which limits users invoke the credential show method for customized times in each epoch determined by the certificate authority. The users could also redact their credentials to realize selective disclosure. We then evaluate the proposed scheme’s performance and present a comparative summary to demonstrate potential utility.

Group signatures are active cryptographic topics where group members are granted right to sign messages anonymously on behalf of their group. However, in practical applications, such rights are not permanent in most cases and are usually limited to some time periods. This means that the signing right of each group member needs to be associated with time periods such that it can be automatically changed with the latter. Among the known approaches, verifier local revocation (VLR) seems to be the feasible one to implement the above functionality, but it will cause an inefficient verification process when the group size is large. In this paper, we describe a group signature scheme with time-bound keys, based on the hardness of lattice assumption, which implements the limitation of the signing right to any time period by constructing a lattice-based redactable signature scheme. Our scheme still adds VLR mechanism for some members who need to revoke prematurely, but the time-bound keys function ensures such members are only a small fraction that do not incur excessive cost for revocation check. We give implementation for our scheme under 93-bit and 207-bit security respectively to demonstrate the practicability – all costs are independent of the group size and achieve a relatively efficient level.

Data management services provided by the public cloud can economize the enterprise’s local storage costs, and meanwhile, realize data sharing among the enterprise. Corporate users, however, usually have concerns about the security and privacy of their data stored in the public cloud. Searchable encryption has been used as a secure method for enterprise users in the public cloud to share data via keyword search for many years. Nevertheless, conventional search and encryption primitives are challenging to realize several critical functions flexibly, such as key update, user revocation, lightweight computation, and low communication overhead for users, which will impede their widespread application. Besides, it may cause single-key-exposure security concerns by using untrusted devices. To address these issues, we present a dynamic consensus committee-based for secure data sharing with authorized multi-receiver searchable encryption (called DCC-SE), which exploits the blockchain dynamic committee to eliminate a single-key-exposure problem and enables fast keyword search without pairing and dynamic user management. The proposed DCC-SE scheme enjoys minor computation and communication overheads. It maintains a constant ciphertext size as the receiver increases. Furthermore, it periodically supports secure key and ciphertext updating and has been proven secure against chosen plaintext attacks and the chosen keyword guessing attacks under the random oracle model. The performance evaluation results show that DCC-SE has more feasibility and higher efficiency than the previous public key with keyword search(PEKS) schemes through theoretical analysis and simulation studies.

Data sharing is an integral part of vehicular ad hoc networks (VANETs), which provide drivers with safe and comfortable driving environments. However, when data are shared among multiple vehicles, they must be encrypted multiple times. Some solutions have used identity-based broadcast encryption to solve this problem. However, these schemes have two major limitations. First, the decryption cost is linearly related to the number of data receivers, where the identity of other receivers must be known. Second, only the data sender can forward the data. To address these important deficiencies, we propose an identity-based broadcast proxy re-encryption scheme to realize flexible and efficient data-sharing in VANETs. The data sender generates a fixed ciphertext that can be obtained by newly added vehicles through authorized vehicles. Data receivers can decrypt ciphertext directly without knowing the identities of other receivers, where the decryption overhead is constant. In addition, our scheme can achieve complete anonymous data sharing to protect vehicle privacy. A security proof shows that our scheme has sufficient security, and a performance analysis shows that our scheme performs well. Our proposed scheme is thus suitable for securing VANETs.

Owing to the open Industrial Internet of Things (IIoT) environment, information interacting between devices and servers is transmitted over the public channel, which may lead to privacy breach of the device identity. Furthermore, communication entities are not fully trusted, and they may maliciously disclose the device identity information. Therefore, the anonymity of devices must be guaranteed. In addition, IIoT is resource-constrained, and complex algorithms are unsuitable for the IIoT system. Several researchers have attempted to design anonymous authentication schemes. The one-authentication-multiple-access approach allows devices to access server resources multiple times after a single authentication, and its authentication overhead is independent of the number of accesses. This can reduce the computational burden for devices that need to access the server frequently. However, existing anonymous authentication schemes do not support multiple accesses after one authentication, and still suffer from privacy issues and low efficiency for devices that need frequent access to the server. To address these issues, we propose a new anonymous authentication scheme that uses group signature technology to ensure device anonymity and uses Merkle hash tree technology to achieve multiple accesses after one authentication, thereby greatly reducing the authentication overhead of IIoT devices. Then, we validate the security of the scheme using the random oracle model and the BAN logic. Finally, compared with other related schemes, the experimental results show that our proposed scheme is more efficient and practical for resource-constrained IIoTs than other schemes.

Edge computing is an emerging distributed computing concept that allows edge servers to provide authorized consumers with various on-demand services. Due to highly dynamic and untrustworthy network environments, various potential security concerns (e.g., unauthorized access, data manipulation, and privacy leakage) have been the critical factors restricting the development of edge computing. A recent heterogeneous framework proposed by Dougherty et al. (CCS’21), named APECS, deploys token-based authorization and multiple attribute-based encryption (MABE) to guarantee access control and data confidentiality. While APECS achieves a secure asynchronous access control without the “always-on” cloud, it suffers from privacy leakage (caused by the public identity information) and fake data spreading issues (due to the data confidentiality). In this paper, we propose an Anonymous and Auditable Distributed Access Control Framework for Edge Computing (AADEC) to relieve these issues. AADEC is based on two building blocks that we designed, namely a conditional anonymous authentication and an auditable MABE with optimized performance. We also define the formal security models and present security proofs for our proposal. The final qualitative comparison and performance benchmark demonstrate that AADEC can achieve a trade-off among anonymity, confidentiality, auditability and efficiency.

Despite the myriad benefits offered by blockchain technology, most of them still face several interrelated issues, such as limited transaction throughput, exorbitant transaction fees, and protracted confirmation times. Payment channel networks have emerged as a promising scalability solution, allowing two mutually distrustful users to engage in multiple off-chain transactions. However, existing schemes based on Hash Time Lock Contract or Anonymous Multi-hop Lock generally cannot ensure strong unlinkability of payments, due to the fact that the time-lock information still remains on the blockchain. To enhance on-chain privacy, a versatile tool was recently proposed by Thyagarajan et al. (CCS’20), namedVerifiable Timed Signatures, but it suffers from the dual insufficiencies of linear-increasing performance and time unverifiability (i.e., performance is linear to the number of signature shares, and signatures cannot be ensured recoverable after the specified time). In this paper, we first propose an approach to reduce computational overhead of VTS, which can be applied to enhance other established schemes, such as VTD (S&P’22) and VTLRS (ESORICS’22). To further reduce the computational complexity fromO(n)toO(1), we introduce a new cryptographic primitive calledVerifiable Timed Adaptor Signatures. Moreover, we extend the VTAS to VTAS+which provides the security property of verifiable recovery. We demonstrate the practicality of our proposal via presenting a concrete instantiation and constructing a privacy-enhanced payment channel network. Finally, the comprehensive evaluation reveals that our solutions exhibit superior performance than the state-of-the-art schemes.

Industrial Internet of Things (IIoT) is revolutionizing plenty of industrial applications by utilizing large-scale smart devices in manufacturing and industrial processes. However, IIoT is facing the disclosure of identity privacy. The identity information is precious and critical, thereby inspiring a line of follow-up privacy-preserving studies, i.e., anonymous credential protocols, or privacy-preserving identity management schemes. However, they are either too anonymous to be used in the IIoT environment, or the system is highly centralized, which implies the risk of a single point of failure. In this article, we proposePBidm, a privacy-preserving blockchain-based identity management scheme for IIoT. Specifically, by leveraging blockchain and diversified cryptographic tools,PBidmcan fully support the desirable properties, i.e., unforgeability, blindness, unlikability, traceability, revocability, and public verifiability. Then, we provide security analysis to ensure reasonable security assurance. Finally, we present a performance evaluation of the proposed scheme to demonstrate the practicability in IIoT applications.

This article focuses on the so-called locally-APN power functions introduced by Blondeau, Canteaut and Charpin, which generalize the well-known notion of APN functions and possibly more suitable candidates against differential attacks. Specifically, given two coprime positive integers$m$and$k$such that$\gcd (2^{m}+1,2^{k}+1)=1$, we investigate the locally-APN-ness property of the Niho type power function$F(x)=x^{s(2^{m}-1)+1}$over the finite field$\mathbb {F}_{2^{2m}}$for$s=(2^{k}+1)^{-1}$, where$(2^{k}+1)^{-1}$denotes the multiplicative inverse modulo$2^{m}+1$. By employing finer studies of the number of solutions of certain equations over finite fields, we prove that$F(x)$is locally-APN and determine its differential spectrum. We emphasize that computer experiments show that this class of locally-APN power functions covers all Niho type locally-APN power functions for$2\leq m\leq 10$. In addition, we also determine the boomerang spectrum of$F(x)$by using its differential spectrum, which particularly generalizes a recent result by Yan, Zhang and Li.

With the application of wireless sensor network (WSN) in healthcare field, online sharing of medical data has attracted more and more attention. However, wearable sensor nodes are limited in energy, storage space and data processing capacity, which largely restricts their deployment in resource demand application scenarios. Fortunately, cloud storage services can enrich the capabilities of wearable sensors and provide an effective method for people to share data within a group. However, as medical data directly relates to patients' health and privacy information, ensuring the integrity and privacy of medical records stored in cloud servers becomes a key issue to be urgently solved. Many public data auditing schemes have been put forward to address the above issues. Unfortunately, most of them have security vulnerabilities or poor functionality and performance. In this paper, we come up with a secure and efficient certificateless public auditing scheme for cloud-assisted medical WSNs, which not only supports dynamic data sharingand privacy protection, but also achieves efficient group user revocation. Security analysis and performance evaluation demonstrate that our scheme significantly reduce the total computation cost while achieving a higher security level. Compared with other related schemes, our new proposal is more suitable for group user data sharing in cloud-assisted medical WSNs.

Traffic route management is essential for reducing traffic jams and enhancing driving safety because of the growing number of vehicles and frequent occurrence of traffic accidents. However, in vehicular ad-hoc networks (VANETs), real-time messages are transmitted via wireless channels, which can result in security and privacy concerns. Existing proposals for traffic route management exist security vulnerabilities, as well as high calculation and communication costs. Encouraged by this fact, we design a lightweight traffic route management scheme for fog-based VANETs. In this scheme, vehicles utilize homomorphic encryption to encrypt their driving routes and then send the encrypted information to a fog node. The traffic management center (TMC) decrypts the received ciphertexts that are aggregated by the fog node and performs traffic management according to the decrypted data, without knowing individual route of each vehicle. Furthermore, blockchain is used in the scheme to conduct public keys management of vehicles. Our detailed security proof and analysis indicate that our proposal can meet the security objectives of VANETs. Further, to demonstrate the feasibility of the scheme, we also implement it in the Ethereum test network (i.e., Rinkeby). Significantly, the performance analysis demonstrates that our proposal achieves a better performance than other relevant representative schemes.

With the continuous innovations and development in communication technology and intelligent transportation systems, a new generation of vehicular ad hoc networks (VANETs) has become increasingly popular, making VANET communication security increasingly important. An intrusion detection system (IDS) is an important tool for detecting network attacks and is an effective means of improving network security. However, existing IDSs encounter several problems involving inaccurate detections, low detection efficiencies, and incomplete detections owing to extensive changes in vehicle locations in VANETs. This study explores federated learning in software-defined VANETs and designs an efficient and accurate collaborative intrusion detection system (CIDS) model. The model utilizes the collaboration among local software-defined networks (SDNs) to jointly train the CIDS model without directly exchanging local network data flows to improve the expansibility and globality of IDSs. To reduce the model difference between different SDN clients and improve the detection accuracy, this study regards the prediction loss for each SDN client as an objective from the perspective of constrained multi-objective optimization. By optimizing a surrogate maximum function containing all the objectives, the method adopts two-stage gradient optimization to achieve Pareto optimality for SDN clients with the worst fairness constraint maximization performance. In addition, this study evaluates the training model using two open-source datasets and compares it with the latest methods. Experimental results reveal that the proposed model ensures local data privacy and demonstrates high accuracy and efficiency in detecting attacks and is thus superior to the current schemes.

As the disruptor of cloud storage, decentralized storage could lead to a major shift in how organizations store data in the future. To ensure data availability, users generally encrypt the data and distribute it to multiple storage service providers. It is necessary to study data integrity verification in decentralized storage. Although some recent studies have proposed the using blockchain technology to assist auditing work in decentralized storage networks, the on-chain overhead still increases linearly with an increase in audit requests. Blockchain networks will inevitably be overloaded. In this study, we propose an efficient data integrity auditing scheme for multiple copies in decentralized storage. Particularly, using different polynomial commitment schemes, we first propose a basic scheme for verifying multiple copies of a single file, and then we propose an efficient batch auditing scheme for multiple copies of multiple files. Our scheme can significantly reduce the computation overhead of storage service providers while keeping the on-chain storage overhead constant. Security analysis and performance analysis show that our scheme is efficient and practical.

Ethereum leverages ECDSA as the digital signature scheme to validate transactions. From the provable security standpoint, ECDSA built on an 80-bit security Elliptic Curve group can achieve at most 50-bit concrete security, rather than 80-bit security, due to its reduction loss for$2^{30}$signature queries in security analysis. The state-of-the-art ECDSA scheme comes with no de facto formal security guarantee. Although there have been many signatures with higher concrete security, their structures are quite different from ECDSA and a total replacement of the signature field in Ethereum will incur high deployment cost. In this work, we present EthereumX without compromising the signature structure in Ethereum while achieves better security. The security gain is built on top of a new technique named randomness preprocessing module (RPM), which can securely pre-generate and verify randomness with the help of Ethereum. Calling RPM allows to pre-select randomness, which will be used for the subsequent signature, and to verify the randomness, assuring that it is previously generated. We give an instantiation with formal security guarantee and prove that it can be improved to 80-bit concrete security under the same discrete logarithm assumption as ECDSA. From this instantiated scheme, we implement EthereumX via a deployment into a locally simulated network. Experiment results show that EthereumX costs 5 seconds for a block generation which is equal to Ethereum, and generates/verifies at least$17017/10623$transactions per second that is practical enough in application, even if they are slightly slower than Ethereum which generates/verifies at least$17908/11257$transactions per second. We also mention that RMP can be applied to other DL-based signatures for the security improvement.

Electronic Medical Records (EMRs) sharing enhances healthcare and biomedical discoveries but faces challenges: data provider centralization and limited interoperability. Blockchain can address these issues, but existing systems struggle with malicious EMR propagation due to challenges concerning the authenticity, non-repudiation, and integrity of the digital signatures they employ. Universal Designated Verifier Signature Proof (UDVSP) may be an intuitive solution, but existing UDVSP schemes are inefficient due to time-consuming bilinear pairing operations. In this article, we first adopt the Elliptic Curve Digital Signature Algorithm (ECDSA) to propose a more efficient and blockchain-friendly UDVSP scheme, following by a blockchain-based EMR sharing system (EMRChain). To our best knowledge, our proposed UDVSP scheme is the first bilinear pairing-free solution, and EMRChain is the first blockchain-based EMR sharing system to possess the anti-malicious propagation. Furthermore, we proceed to provide a thorough security analysis and performance evaluation of both our UDVSP scheme and EMRChain. Our UDVSP scheme is provably secure within the security model and offers significant computational cost savings (at least 86.76%) and reduced communication overhead (at least 59.37%) compared to existing UDVSP schemes. These results, along with the EMRChain prototype, effectively showcase the utility and effectiveness of EMRChain, which is built upon our UDVSP scheme.

Nowadays, data privacy is one of the most critical concerns in cloud computing, and many privacy-preserving distributed computing systems based on the trusted execution environment (e.g., Intel SGX) have been proposed to protect the user's privacy during cloud-outsourced computation. However, these SGX-based solutions are vulnerable to some traffic analyses, and loading all tasks into the enclave introduces much overhead for frequent EPC-paging. In this paper, we propose a T-SGX framework, which keeps the confidentiality of a distributed job and guarantees the system efficiency by allowing dynamically loading an enclave shared object for the task under processing. In T-SGX, all these objects are secretly shared and stored in a verifiably distributed share management system (SMS) outside the TCB. To mitigate the exposure of sensitive information, we present an efficient oblivious transfer (OT) protocol under the Decisional Diffie-Hellman (DDH) assumption for obliviously transmitting desired shares. Detailed security analysis demonstrates that the proposed T-SGX achieves the goal of secure distributed computing without privacy leakage to unauthorized parties. Finally, we benchmark the framework in six real-world applications, and the experimental results show that T-SGX significantly outperforms a state-of-the-art solution, with 11.9%-29.7% less overhead performing an SGX-based application.

Solving the system of linear algebraic equations (LAE) is the most well known and probably the most important of all numerical computations involving real numbers. Researchers have been committed to developing distributed algorithms to solve such systems for a long time. However, traditional distributed algorithms have serious security risks when the coefficients and the solution are of great value. To address the privacy issue, we propose a new secure distributed outsourcing protocol for solving large-scale LAE systems. Specifically, we give an algorithm for generating a generic repeatedly jointly strongly connected sequence, for the first time as far as we know. Then we embed the matrix masking technique in our distributed system requiring multiple rounds of iteration while keeping the correctness of convergence. In addition, for the first time, we give a method for discriminating by the agents under masking whether the plaintext approximate solution corresponding to the current masked solution satisfies a predetermined constraint. Finally, we give the experimental result to show the practicality of our new protocol.

Abstract SM9 is a Chinese cryptography standard, which includes a set of identity-based cryptographic schemes over pairings. SM9 identity-based signature scheme (SM9-IBS) was standardized by ISO/IEC and has been widely used in many real-world applications such as blockchain. Nevertheless, the signing algorithm of SM9-IBS suffers from several heavy calculations (e.g. pairings, scalar multiplications in groups), which might be a bottleneck for lightweight devices such as sensors. In this paper, we modify the SM9-IBS scheme slightly to support fast signing. In order to achieve this, we make the use of online/offline methodology and propose a new online/offline IBS scheme based on SM9. The proposed scheme is proved to be EUF-sID-CMA secure and is about 99% faster than SM9-IBS in terms of signature generation. Precisely, the time cost of online signing is <1 ms. Our scheme is appropriate for the Internet of Things. The theoretical analysis and demonstration show that the proposed scheme is comparable to existing efficient online/offline IBS schemes.

Ensuring the security and privacy of users and data in a mobile-edge computing (MEC) deployment, without affecting performance, latency and user quality of experience remain challenging. For example, in this article, we revisit an identity-based anonymous authentication scheme designed for MEC deployment. Then, we reveal that the scheme is vulnerable to impersonation, replay, and Denial-of-Service (DoS) attacks, contrary to their claims. It also does not achieve user untraceability, and the registration center must be online during authentication. We also observe that it is unclear from their scheme description, what encryption algorithm should be used in the authentication process. Therefore, we redesign the scheme in order to mitigate the weaknesses pointed out. Our redesigned protocol uses password and biometrics for authentication, which broadens the scope for real-world implementation. We also provide both formal security proof and heuristic security analysis to demonstrate that the proposed scheme achieves the desired security goals. A performance comparison shows that our scheme outperforms four other competing schemes in terms of computation and communication costs.

Benefiting from the progress of Internet of Things (IoT) technology, medical devices, wearables, sensors, and users can be connected with each other to form an Internet of Medical Things (IoMT) ecosystem. IoMT improves efficiency, increases accuracy, and reduces the costs of the traditional healthcare system. However, since IoMT involves different entities and heterogeneous networks and carries a large amount of private information, it is a challenging task to ensure data security and protect privacy in the IoMT ecosystem. In this article, we focus on the issue of privacy-aware authentication between entities. We first propose a blockchain-assisted authentication framework for IoMT applications in the fog computing paradigm. Furthermore, we present two privacy-preserving authentication protocols based on elliptic curve cryptography (ECC) and physically unclonable functions (PUFs), respectively, in terms of the capacity of involved entities. Security analysis and performance evaluation demonstrate that compared with several previous protocols, the proposed protocols have competitive computation and communication costs while achieving expected security requirements.

The Internet of Things (IoT) devices possessed by individuals produce massive amounts of data. The private data onto specific IoT devices can be combined with intelligent platform to provide help for future research and prediction. As an important digital asset, individuals can sell private data to get rewards. Problems, such as privacy, security, and access control prevent individuals from sharing their private data. The blockchain technology is widely used to build an anonymous trading system. In this article, we construct a blockchain-based privacy-preserving and rewarding private data-sharing scheme (BPRPDS) for IoT. A privacy issue worth considering is that the malicious cloud server may establish a behavior profile database of data users (DUs). In the case of anonymity, the transactions of private data sharing are easy to cause disputes. When anonymous DUs are framed, it is hard to protect their rights. With the help of the deniable ring signature and Monero, we realize the behavior profile building prevention and nonframeability of BPRPDS. At the same time, we utilize the licensing technology executed by smart contracts to ensure flexible access control of multisharing. The proposed BPRPDS is provably secure. Performance analysis and experimental results show that BPRPDS is efficient and practical.

In wireless sensor networks (WSNs), data aggregation (DA) has become one of the most practical techniques to reduce processing delay and improve energy efficiency. To support intelligent applications, sensor nodes need to report heterogeneous and diverse data, which induce the demand for multidimensional DA and multifunctional data analysis. To solve the current security problems and functional requirements, we propose a multifunctional and multidimensional secure DA scheme to strike the balance between data availability and privacy. First, we design a Chinese remainder theorem conversion method with the counter to encode multidimensional data into large integers, which can be operated by linear homomorphic encryption schemes. Then, we introduce a multifunctional data analysis method supporting diversified aggregation functions, including linear, polynomial, and continuous functions. Moreover, we demonstrate that the proposed scheme can achieve confidentiality, integrity, authentication, and resistance against false data injection attacks. The experimental results show that the supported max dimension of one ciphertext in our scheme is at least twice that of existing schemes. Thus, in scenarios with high dimensions, our scheme is superior to the existing schemes in terms of computation and communication costs.

Internet of Things (IoT) enables terminal devices connecting with the Internet and provides various intelligent applications by analyzing devices data. As a typical IoT technique, edge computing provides a three-tier architecture to reduce communications and improve efficiency. Specifically, edge nodes are responsible for collecting and aggregating device data, and then send processed results to the cloud for subsequent analysis. However, the data aggregation function will compromise the privacy of device data. In this article, we proposed an efficient privacy-preserving multidimensional data aggregation scheme for IoT, called PMDA. The scheme uses the Chinese remainder theorem to design a homomorphic encryption method that encryptes a multiple-dimensional small integer vector into one ciphertext and keeps linear homomorphic properties per dimension. Combining with the signature mechanism and the batch verification method, the scheme guarantees nonrepudiation of device data and enhance verification efficiency at edge nodes. Through theoretical analysis, we demonstrate that the proposed scheme can achieve correctness, privacy, authentication, and integrity. After performance evaluation, we demonstrate that our scheme is superior to other schemes in terms of computation and communication costs. In particular, as the message dimension increases, our scheme computation costs almost a tenth of others at the 80-bits security level.

Internet of Vehicles (IoV) being a subdivided application of the Internet of Things, is considered as one of the most prominent and emerging technologies for model transportation systems. However, security and privacy remain two key requirements for IoV networks, as communications between vehicles and other Internet-connected things are generally carried out over public channels. Some of the most typical attack issues for the IoV networks include hardware tampering, unauthorized data access, message modification, tracking vehicle locations, etc. Although there have been a number of solutions (e.g., mutual authentication and key agreement protocols) proposed to ensure the secure communication for IoV, most of them still suffer from some vulnerabilities, such as linkability, server spoofing, and replay attacks, in violation of the security requirements of IoV. Hence, it remains challenging to design secure and efficient solutions. In this article, we first take a recently proposed authentication protocol as an example and analyze the weaknesses of it with simple mathematical analysis. We then propose an improved multiserver-based authentication and key agreement protocol for IoV (called SeMAV), which applies the password and smart card to hide the private keys. We also present both formal and informal security proofs to confirm the robustness against those commonly known attacks. The theoretical comparative summary and simulation results also show that SeMAV can achieve a good performance when compared with some other related protocols in the literature.

Over the past decade, the Internet of Things (IoT) is widely adopted in various domains, including education, commerce, government, and healthcare. There are also many IoT-based applications drawn significant attentions in recent years. With the increasing numbers of the connected devices in the IoT system, one of the challenging tasks is to ensure devices’ authenticity, which allows users to have a high confidence in the decision. In addition, due to the heterogeneity of the IoT system and the resource-constrained devices, how to efficiently manage such system and guarantee the security and privacy for devices is concerned. In this article, we proposed a new blockchain-based authentication scheme to meet the challenges. Our proposed framework combines the blockchain technique and the modular square root algorithm to achieve an effective authentication process. Besides, we demonstrate the security and utility of the proposed scheme by providing the security analysis and the detailed experiment.

In cloud storage, how to search sensitive data efficiently and securely is a challenging problem. The searchable encryption technique provides a secure storage method without loss of data confidentiality and usability. As an important branch of searchable encryption, public-key encryption with keyword search (PEKS) is widely studied by scholars. However, most of the traditional PEKS schemes are vulnerable to the inside keyword guessing attack (IKGA). Resisting the inside keyword guessing attack is likely to become an essential property of all new PEKS schemes. For a long time, mitigating IKGA has been inefficient and difficult, and most existing PEKS schemes fail in achieving their security goals. To address the above problems, we define the notion ofDual-serverPublic-keyAuthenticatedEncryption withKeywordSearch (DPAEKS), which protects against IKGA by leveraging two servers that do not cooperate, and supports the authentication property. Then, we provide a construction of DPAEKS without bilinear pairings. Experimental results obtained using a real-world dataset show that our scheme is highly efficient and provides strong security, making it suitable for deployment in practical applications.

In the digital twin environment, the fusion data onto physical entities in the physical space are mapped to multiple virtual spaces for digital modeling and intelligent simulation in different dimensions. In real intelligent manufacturing scenarios, heterogeneous multi-source fusion data are collected at the same time period. So they are consistent in time state. For the autonomous digital twin system, time states verification and integrity checking are basic security factors. Provable data possession technology can check the integrity of data onto virtual spaces. The blockchain can provide the synchronization interface to make distributed entities to obtain the trusted time state value. Considering the privacy, the blockchain can also provide anonymous services for entities. Therefore, we propose the blockchain-based synchronized provable data possession scheme (named BSPDP) for digital twin. In our scheme, the selection of verifier is flexible. Since virtual spaces may be maliciously framed to pay compensation, we use tag verification to prevent honest virtual spaces from being framed. Under the assumption of RSA, the proposed BSPDP is provably secure. Finally, the performance analysis demonstrates that BSPDP is practical. The experimental results show that BSPDP is effective and attractive for digital twin.

Security in the Industrial Internet of Things (IIoT) is vital as there are some cases where IIoT devices collect sensory information for crucial social production and life. Thus, designing secure and efficient communication channels is always a research hotspot. However, end devices have memory, computation, and power-supplying capacities limitations. Moreover, perfect forward secrecy (PFS), which means that long-term key exposure still discloses previous session keys, is a critical security property for authentication and key exchange (AKE). This article proposes an AKE protocol named SAKE* for the IIoT environment, where two types of keys (i.e., a master key and an evolution key) guarantee PFS. In addition, the SAKE* protocol merely uses concatenation, XOR, and hash-function operations to achieve lightweight authentication, key exchange, and message integrity. We also compare the SAKE* protocol with seven current and IoT-related authentication protocols regarding security properties and performance. Comparison results indicate that the SAKE* protocol consumes the least computation resource and third-least communication cost among eight AKE protocols while equipping 12 security properties.

Federated learning, as a typical distributed learning paradigm, shows great potential in Industrial Internet of Things, Smart Home, Smart City, etc. It enables collaborative learning without data leaving local users. Despite the huge benefits, it still faces the risk of privacy breaches and a single point of failure for aggregation server. Adversaries can use intermediate models to infer user privacy, or even return incorrect global model by manipulating the aggregation server. To address these issues, several federated learning solutions focusing on privacy-preserving and security have been proposed. However, theses solutions still faces challenges in resource-limited scenarios. In this paper, we propose G-VCFL, a grouped verifiable chained privacy-preserving federated learning scheme. Specifically, we first use the grouped chain learning mechanism to guarantee the privacy of users, and then propose a verifiable secure aggregation protocol to guarantee the verifiability of the global model. G-VCFL does not require any complex cryptographic primitives and does not introduce noise, but enables verifiable privacy-preserving federated learning by utilizing lightweight pseudorandom generators. We conduct extensive experiments on real-world datasets by comparing G-VCFL with other state-of-the-art approaches. The experimental results and functional evaluation indicate that G-VCFL is efficient in the six experimental cases and satisfies all the intended design goals.

Dispatching and Control Cloud (DCC) is a cloud platform constructed by State Grid Corporation with the technology of cloud computing. DCC has improved the overall operation and monitoring capabilities, the smart level and many other advantages of power grid. However, the development of DCC has been hampered by security and privacy issues. Secure unified identity authentication, access control and authorisation management are significant topics in DCC. To find out a solution for the topics above, we have employed some encryption schemes using the attribute-based encryption(ABE), as ABE can preserve users' privacy and achieve access control with fine grain over the encrypted information. SM9 is a kind of Chinese official standard in the field of cryptography, which contains the SM9 encryption algorithm (SM9-IBE). In this paper, an ABE scheme based on SM9-IBE is proposed, making SM9 support fine-grained access control which would be better applied in DCC. Our proposed scheme (SM9-ABE) has been proven to be of great security in the selective CPA model under DBDH assumption. Furthermore, we implement SM9-ABE and evaluate its practical performance. The implementation indicates our scheme performs well in the matter of security and functionality, at an additional time cost which is acceptable.

The Internet of Things (IoT) is gradually stepping out of its infancy into maturity. Its widespread applications cover from tiny wearable devices to large industrial systems. Although many security solutions have been introduced to address data security and privacy problems caused by the unique characteristics of IoT, how to simultaneously achieve data confidentiality, protect the privacy of access control policy, and provide reasonable data source identification has been a challenging problem. Moreover, lacking one of the above properties may result in serious issues (e.g., leakage information and forging identity), and the situation grows steadily worse with the expansion of “things” scale. To address the above issues, we propose a new cryptographic primitive named certificateless matchmaking encryption (CL-ME), which inherits the security properties of certificateless cryptosystem and matchmaking encryption. Meanwhile, we also present two effective concrete constructions with formal security proofs based on the standard hard assumptions. The basic construction is the first instance of CL-ME based on bilinear pairing, and the enhanced construction is a pairing-free lightweight solution. Finally, we implement our proposed schemes using popular cryptography library and compare their performance with existing works. Theoretical analysis and experimental evaluations demonstrate that our proposed schemes are more suitable for IoT environment.

For large-scale data transmission of the Industrial Internet of Things (IIoT), aggregate signature is an effective approach. It can compress the signatures of different senders to save bandwidth. In order to maintain the autonomous management of IIoT, massive sensing data are sent to the data center for intelligent analysis. The reliability of data is an important guarantee of the autonomous management of IIoT. Tracing abnormal senders is a challenge when hiding their real identity. Therefore, we design the first permissioned blockchain-based anonymous and traceable aggregate signature (PBATAS) scheme for IIoT. Smart contracts are used to authenticate anonymous sources and share cryptographic materials among entities, providing reliable regulatory support for IIoT. The regulator can quickly trace the abnormal data sources recorded on the blockchain, which is practical for the anonymous IIoT environment. Through the formal security proof of conditional anonymity, unforgeability, traceability, and resistance to coalition attacks, the proposed PBATAS is provably secure. Performance analysis demonstrates that PBATAS is effective.

Wireless body area networks (WBANs) have become more commonplace, including in healthcare settings. For example, in a healthcare WBAN deployment, body sensor units (BSUs) are used to sense and collect health-related and medical-related information prior to sending relevant information to the server for analysis that can subsequently inform treatment plan. Given the sensitivity of both data-at-rest and data-in-transit, data authentication is fundamental to the success of such systems. However, BSUs are generally resource constrained and, hence, conventional cryptographic algorithms are not practical. Therefore, in this article, we propose an efficient certificateless online/offline signature scheme and design a lightweight data authentication protocol for WBANs. We then evaluate the security and performance of our proposed scheme, where the security analysis demonstrates that the proposed scheme satisfies existential unforgeability under the random oracle model. Findings from the performance evaluation also demonstrate that our scheme incurs very low computational cost during the signing operations. In comparison to several other competing approaches, our proposed scheme achieves a significant reduction in computational cost (up to 89%) for the offline signer and supports batch verification to reduce the verifier's execution time. In addition, we also show that the signature size of our proposed scheme is similar to those of the conventional signature schemes.

As the use of machine learning in the Internet-of-Medical Things (IoMT) settings increases, so do the data privacy concerns. Therefore, in this article, we propose an efficient privacy-preserving outsourced support vector machine scheme (EPoSVM), designed for IoMT deployment. To securely train the support vector machine (SVM), we design eight secure computation protocols to allow the cloud server to efficiently execute basic integer and floating-point computations. The proposed scheme protects training data privacy and guarantees the security of the trained SVM model. The security analysis proves that our proposed protocols and EPoSVM satisfy both security and privacy protection requirements. Findings from the performance evaluation using two real-world disease data sets also demonstrate the efficiency and effectiveness of EPoSVM in achieving the same classification accuracy as a general SVM.

The rapid development of the Internet of Things (IoT) has led to the emergence of more and more novel applications in recent years. One of them is the e-health system, which can provide people with high-quality and convenient health care. Meanwhile, it is a key issue and challenge to protect the privacy and security of the user's personal health record. Some cryptographic methods have been proposed such as encrypt user's data before sharing it. However, it is complicated to share the data with multiple parties (doctors, health departments, etc.), due to the fact that data should be encrypted under each recipient's keys. Although several (t, n) threshold secret sharing schemes can share the data only need one encryption operation, there is a limitation that the decryption private key has to be reconstructed by one party. To offset this shortcoming, in this paper, we propose an efficient identity-based distributed decryption scheme for personal health record sharing system. It is convenient to share their data with multiple parties and does not require to reconstruct the decryption private key. We prove that our scheme is secure under chosen-ciphertext attack (CCA). Moreover, we implement our scheme by using the Java pairing-based cryptography (JPBC) library on a laptop and an Android phone. The experimental results show that our system is practical and effective in the electronic personal health record system.

There has been increased interest in applying artificial intelligence (AI) in various settings to inform decision-making and facilitate predictive analytics. In recent times, there have also been attempts to utilize blockchain (a peer-to-peer distributed system) to facilitate AI applications, for example, in secure data sharing (for model training), preserving data privacy, and supporting trusted AI decision and decentralized AI. Hence, in this paper, we perform a comprehensive review of how blockchain can benefit AI from these four aspects. Our analysis of 27 English-language articles published between 2018 and 2021 identifies a number of research challenges and opportunities.

As an important security property of cloud storage, data integrity has not been sufficiently studied under the multi-writer model, where a group of users work on shared files collaboratively and any group member can update the data by modification, insertion, and deletion operations. Existing works under such multi-writer model would bring large storage cost to the third-party verifiers. Furthermore, to the best of our knowledge, none of the existing works for shared files supports fully dynamic operations, which implies that users cannot freely perform the update operations. In this paper, we propose the first public auditing scheme for shared data that supports fully dynamic operations and achieves constant storage cost for the verifiers. Our scheme, named PRAYS, is boosted by a new paradigm for remote data integrity checking. To implement the new paradigm, we proposed a specially designed authenticated structure, called blockless Merkle tree, and a novel cryptographic primitive, called permission-based signature. Extensive evaluation demonstrates that PRAYS is as efficient as the existing less-functional solutions. We believe that PRAYS is an important step towards designing practical multi-writer cloud storage systems.

We introduce the abstract framework of decentralized smart contracts system with balance and transaction amount hiding property over account-model blockchain. To build a concrete system with such properties, we utilize a homomorphic public-key encryption scheme and construct a highly efficient non-interactive zero knowledge (NIZK) argument based upon the encryption scheme to ensure the validity of the transactions. Our NIZK scheme is perfect zero knowledge in the common reference string model, while its soundness holds in the random oracle model. Compared to previous similar constructions, our proposed NIZK argument dramatically improves the time efficiency in generating a proof, at the cost of relatively longer proof size.

Remote data secure storage is of crucial importance in cloud computing. In order to check remote data integrity, an important paradigm PDP (i.e., provable data possession) is proposed. All the existing PDP schemes make use of RSA or bilinear pairings. One large file has to be divided into a great many of blocks. For example, 1T (Terabit) file has to be divided into$1.0737 \times 10^9$blocks (RSA where the length of the index is 1024 bits) or$6.8719 \times 10^9$blocks (bilinear pairings where the order of the elliptic curve is 160 bits). The huge computation cost and communication cost incurs the inefficient PDP implementation. In other words, they are not practical. In order to solve the problem, we propose a new PDP model: blockchain-based private PDP. The new concept makes use of blockchain which is the core of cryptocurrency. For the new concept, the paper formalizes its system model and security model. Then, a concrete blockchain-based private PDP scheme is designed by making use of blockchain and RSA. The proposed blockchain-based private PDP scheme is provably secure. At the same time, we also analyze its performance from two parts: theory analysis and implementation prototype. Our analysis shows that the proposed PDP scheme is secure, efficient and practical.

Outsourcing computations have been widely used to meet the growing computing demands, although achieving trust in an untrusted (or a zero-trust) environment can be challenging in practice. Fair payment, a candidate solution, can potentially facilitate fair trading among outsourcing computation participants such as users and workers. However, most existing solutions including traditional e-cash-based or blockchain-based, may potentially compromise the worker’s fairness (i.e., does not achieve robust fairness, since trusted third parties are required during the trading process), or involve heavy zero-knowledge proofs (ZKPs, with significant computation costs). To mitigate these limitations, we propose a system model of an optimized blockchain-based fair payment (OBFP) for outsourcing computations. Then, we construct a ZKP-free solution based on blockchain by combining any secure commitment, accumulator, and symmetric encryption schemes, as well as a hash function. To demonstrate the utility of our proposed OBFP system, we provide security analysis, performance evaluation and a comparison with existing popular solutions. Specifically, the cryptographic tools are instantiated as commitment (Perdesen commitment), accumulator (RSA-based accumulator), and symmetric encryption (a concrete scheme with the indistinguishability under chosen-plaintext attack (IND-CPA) security), and a hash function (Keccak-256). The prototype is implemented in COSBench and Remix to analyze cloud scalability and concurrency, as well as gas cost.

Cognitive computing over big data brings more development opportunities for enterprises and organizations in industrial informatics, and can make better decisions for them when they face data security challenges. To satisfy the requirement of real-time data storage in industrial Internet of Things (IoT), the remote unconstrained storage cloud is usually used to store the generated big data. However, the characteristic of semitrust of the cloud service provider determines that the data owners will worry about whether the data stored in cloud computing has been corrupted. In this article, a secure storage auditing is proposed, which supports efficient key updates and can be well used in cognitive industrial IoT environment. Moreover, the proposed basic auditing can be extended to support batch auditing that is suitable for multiple end devices to audit their data blocks simultaneously in practice. In addition, a hybrid data dynamics method is proposed, which employs a hash table to store the data blocks and uses a linked list to locate the operated data block. Compared with previous methods, the data block location time in the proposed data dynamics can be reduced by 40%. The security analysis results demonstrate that the proposed scheme can be proved to be correct, and is secure under computational differ-hellman (CDH) and discrete logarithm (DL) assumptions.

While Vehicular Ad-hoc Networks (VANETs) can potentially improve driver safety and traffic mangement efficiency (e.g. through timely sharing of traffic status among vehicles), security and privacy are two ongoing issues that need to be addressed. Hence, security solutions such as conditional privacy-preserving authentication (CPPA) protocols have been proposed. However, CPPA protocols are generally far from being ready for deployment in VANETs, for example due key/certificate management limitations in PKI-based protocols or intractable private key updating in ID-based protocols. Although serveral blockchain-based CPPA (BCPPA) protocols have been proposed to mitigiate these challenges, there still exist some intractabilities such as revoking private key, or frequent interactions, or requiring an idea hardware. Thus, in this paper, we are motivated to propose a novel BCPPA protocol without these existing issues. Specifically, we present a PKI-based solution (using a typical digital signature protocol, such as ECDSA) based on Ethereum (a public blockchain), which is designed to facilitate secure communication in VANETs. In other words, we combine the blockchain technology and a key derivation algorithm to realize an effective certificate management. This reduces the need for participating vehicles to store a large number of private keys. To reduce the verification time cost, our BCPPA suppotrs replacing ECDSA with modified ECDSA for batch verification or directly adopting other PKI-based signatures with batch verification. In addition to introducing the concrete design, we also present the security requirements that our BCPPA protocol can satisfy. We then implement BCPPA in the Ethereum test network (i.e.Rinkeby) and provide simulations using VanetMobiSim and NS-2 to show its feasibility (i.e. milliseconds).

The Internet of connected Vehicles (IOV) can collect, process, compute and release the information of intelligent transportation systems. IOV is an integrated service system that can support the applications for automatic driving, intelligent transport and information services. As the number of incidents on IOV has been on the rise in the past few years, IOV security is becoming increasingly important in the IOV architecture. One of the most notable risks of IOV faces is intelligent terminal security. The vehicle's intelligent terminal can be used to launch for further attacks on the on-board operating system to penetrate into the internal network of connected vehicle, and consequently threaten the safety of the vehicle. Thus, it is of paramount importance that we protect the security of the intelligent terminal. We propose two intelligent terminal based privacy-preserving multi-modal implicit authentication protocols to protect the security of the intelligent terminal in IOV. The proposed protocols use the password and the vehicle owner's behavior features as the authentication factors to protect the security of the intelligent terminal. Since the vehicle owner's behavior features are sensitive and the privacy information of the user must be protected, we also consider the privacy protection of the behavior features. Our protocols do not reveal any information about the vehicle owner's behavior features to the authentication server and the adversary except the ciphertext size of the feature vector. We analyze the security of our proposed protocol and compare them with other related protocols in terms of computation and communications costs. Our results demonstrate that our proposed protocols yield better security and efficiency.

The sensing-as-a-service (SaaS) model has been explored to address the challenge of intractability of managing a large number of sensors faced by future smart cities. However, how to effectively share sensor data without compromising confidentiality, privacy protection, and fair trading without third parties is one of critical issues that must be solved in the SaaS in smart cities. While blockchain shows promise in solving these issues, the existing blockchain-based data sharing (BBDS) systems are difficult to apply to SaaS in smart cities because of many unresolved issues such as requiring a customized blockchain, huge storage, communication and computation costs, and dependence on a third party to achieve fair trading. We propose a BBDS system model with its security requirements before we present a concrete construction by combining -protocol, Paillier encryption scheme, and any secure symmetrical encryption and signature schemes. To demonstrate the utility of our proposed BBDS system, we present a security analysis and compare our system with other solutions. We implement the prototype in Remix to analyze the gas cost, and we conduct experiments to evaluate the communication and computation costs of the BBDS system using symmetric encryption (advanced encryption standard (AES)) and a signature scheme (elliptic curve digital signature algorithm (ECDSA)).

With the evolvement of the Internet of things (IoT), privacy and security have become the primary indicators for users to deploy IoT applications. In the gateway-based IoT architecture, gateways aggregate data collected by perception-layer devices and upload message packets to platforms, while platforms automatically push different categories of data to different applications. However, security in processes of data transmission via gateways, storage in platforms, access by applications is the major challenge for user privacy protection. To tackle this challenge, this article presents a secure IoT scheme based on a fine-grained multi-receive signcryption scheme to realize end-to-end secure transmission and data access control. To enhance the security of online application decryption keys, we design a distributed threshold decryption scheme based on secret-sharing. Moreover, from the provable security perspective, we demonstrate that the scheme can achieve the expected IND-CCA security and EUF-CMA security. After the performance analysis, evaluation results show that the computational performance is efficient and linearly subject to the number of messages and the number of receivers.

As one of the essential applications of health information technology, the eHealth system plays a significant role in enabling various internet medicine service scenes, most of which primarily rely on service recommendation or an evaluation mechanism. To avoid privacy leakage, some privacy-preserving mechanisms must be adopted to protect raters’ privacy and make evaluation trust reliable. To tackle this challenge, this article proposes an efficient service recommendation and evaluation scheme, called EPRT , which is based on a similarity calculation and trust discovery method. This scheme uses homomorphic encryption technology to encrypt the sensitive data and combines the threshold mechanism and double-trap mechanism to realize the secure computing on the encrypted data, so as to ensure that the plaintexts of the final calculation results (e.g., recommendation value and evaluation truth) are only obtained by the authorized subject. In addition, a detailed security analysis shows that the proposed EPRT scheme can achieve the expected security. In addition, performance comparison results are carried out, demonstrating its effectiveness and accuracy.

Internet of Things (IoT)-enabled smart grids can achieve more reliable and high-frequency data collection and transmission compared with existing grids. However, this frequent data processing may consume a lot of bandwidth, and even put the user’s privacy at risk. Although many privacy-preserving data aggregation schemes have been proposed to solve the problem, they still suffer from some security weaknesses or performance deficiency, such as lack of satisfactory data confidentiality and resistance to malicious data mining attack. To address these issues, we propose a novel privacy-preserving data aggregation scheme (called PDAM) for IoT-enabled smart grids, which can support efficient data source authentication and integrity checking, secure dynamic user join and exit. Unlike existing schemes, the PDAM is resilient to the malicious data mining attack launched by internal or external attackers and can achieve perfect data confidentiality against not only a malicious aggregator but also a curious control center for an authorized user. The detailed security and performance analysis show that our proposed PDAM can satisfy several well-known security properties and desirable efficiency for a smart grid system. Moreover, the comparative studies and experiments demonstrate that the PDAM is superior to other recently proposed works in terms of both security and performance.

As quantum computers become more affordable and commonplace, existing security systems that are based on classical cryptographic primitives, such as RSA and Elliptic Curve Cryptography ( ECC ), will no longer be secure. Hence, there has been interest in designing post-quantum cryptographic ( PQC ) schemes, such as those based on lattice-based cryptography ( LBC ). The potential of LBC schemes is evidenced by the number of such schemes passing the selection of NIST PQC Standardization Process Round-3. One such scheme is the Crystals-Dilithium signature scheme, which is based on the hard module-lattice problem. However, there is no efficient implementation of the Crystals-Dilithium signature scheme. Hence, in this article, we present a compact hardware architecture containing elaborate modular multiplication units using the Karatsuba algorithm along with smart generators of address sequence and twiddle factors for NTT, which can complete polynomial addition/multiplication with the parameter setting of Dilithium in a short clock period. Also, we propose a fast software/hardware co-design implementation on Field Programmable Gate Array ( FPGA ) for the Dilithium scheme with a tradeoff between speed and resource utilization. Our co-design implementation outperforms a pure C implementation on a Nios-II processor of the platform Altera DE2-115, in the sense that our implementation is 11.2 and 7.4 times faster for signature and verification, respectively. In addition, we also achieve approximately 51% and 31% speed improvement for signature and verification, in comparison to the pure C implementation on processor ARM Cortex-A9 of ZYNQ-7020 platform.

With the rapid development of cloud computing, more and more enterprises would like to upload and store their data in the public cloud. When the parts of the business of an enterprise are purchased by another enterprise, the corresponding data will be transferred to the acquiring enterprise. For the usual case, how to outsource the computation cost of data transfer to the cloud? How to ensure the remote purchased data integrity? Thus, it is important to study provable data possession with outsourced data transfer (DT-PDP). In this paper, for the first time, we propose the novel concept: DT-PDP. By taking use of DT-PDP, the following three security requirements can be satisfied: (1) the other un-purchased data security of acquired enterprise can be ensured; (2) the purchased data integrity and privacy can be ensured; (3) the data transferability’s computation can be outsourced to the public cloud servers. For the security concept of DT-PDP, we give its motivation, system model and security model. Then, we design a concrete DT-PDP scheme based on the bilinear pairings. At last, we analyze the security, efficiency and flexibility of the concrete DT-PDP scheme. It shows that our scheme is provably secure and efficient.

Smart grid achieves reliable, efficient and flexible grid data processing by integrating traditional power grid with information and communication technology. The control center can evaluate the supply and demand of the power grid through aggregated data of users, and then dynamically adjust the power supply, price of the power, etc. However, since the grid data collected from users may disclose the user's electricity using habits and daily activities, the privacy concern has become a critical issue. Most of the existing privacy-preserving data collection schemes for smart grid adopt homomorphic encryption or randomization techniques which are either impractical because of the high computation overhead or unrealistic for requiring the trusted third party. In this paper, we propose a privacy-preserving smart grid data aggregation scheme satisfying local differential privacy (LDP) based on randomized response. Our scheme can achieve efficient and practical estimation of the statistics of power supply and demand while preserving any individual participant's privacy. The performance analysis shows that our scheme is efficient in terms of computation and communication overhead.

In cryptocurrency and blockchain-based distributed ledgers, transfer of money (digital coins) can be presented as a transaction. Due to the irreversibility nature of blockchain transactions, a single fraudulent use of private key (used to sign transactions) could have significant consequences (e.g. financial loss). Key protection alone is not adequate in protecting cryptocurrencies, and threshold signature is a viable method to avoid fraudulent key usage or key theft. In this paper, we focus on the Edwards-curve digital security algorithm (EdDSA), which has been applied in several cryptocurrencies (e.g. Cardano, Zcash, and Decred) and design the first efficient two-party EdDSA signing protocol. Unlike standard secret sharing, a valid signature is generated using an interactive protocol without the original key ever being exposed. We mathematically prove the security of our proposed protocol. Findings from the performance evalation of the protocol show that it achieves good performance for curve Ed25519, with a single signing operation in the malicious setting taking approximately 3.32 ms between two devices.

The identity‐based signature (IBS) scheme is one of the most promising secure and widely used cryptographic primitives for electronic commerce applications. For example, ID‐based signing in a multi‐party setting, without ever revealing any private and secret information , has received considerable interest in distributed applications such as a global manufacturer. However, there is no practical solution for such a group setting (e.g. more than two parties). Therefore, in this study, the authors present the first distributed identity‐based signing protocol for the global electronic commerce system. Specifically, the authors’ designed protocol allows a group of parties to generate the signature in a decentralised and fair manner. They also prove that their proposed protocol is secure against a malicious adversary under the discrete logarithm and decisional Diffie–Hellman assumptions. Moreover, they implement the protocol using the MIRACL libraries on physical computing devices. Findings from the evaluations demonstrate the practical utility of their proposed protocol, in terms of achieving high level of security within a reasonable time framework (e.g. signing time (including communication latency and waiting delay) takes 311.86 ms for three parties, 558.2 ms for five parties, and 707.21 ms for seven parties, under a single‐thread implementation).

Identity‐based cryptography (IBC) is considered as a promising mechanism in the Internet of Things and ad‐hoc networks, providing lightweight authentication and powerful access control. However, it suffers from two inherent problems, i.e. key escrow and the requirement of a secure channel, which are not always good properties in many realistic scenarios. Thus, an efficient key issuing protocol in a distributed setting without the assumption of the secure channel is needed. In this study, the authors give special attention to the IBC standardised in IEEE P1363 and design a multi‐party setup and key issuing protocol for it. Their protocol is proven to be malicious secure by simulation under weaker assumptions. Contrast to prior works that rely on a trusted party for key distribution or the strong assumption of a secure channel, they provide the first practical solution for the distributed architectures.

Increasingly, governments around the world, particularly in technologically advanced countries, are exploring or implementing smart homes, or the related smart facilities for the benefits of the society. The capability to remotely access and control Internet of Things (IoT) devices (e.g., capturing of images, audios, and other information) is convenient but risky, as vulnerable devices can be exploited to conduct surveillance or perform other nefarious activities on the users and organizations. This highlights the necessity of designing a secure and efficient remote user authentication solution. Most of the existing solutions for this problem are generally based on a single-server architecture, which has limitations in terms of privacy and anonymity (leading to users' daily activities being predicted), and integrity and confidentiality (resulting in an unreliable behavior auditing). While blockchain-based solutions may mitigate these issues, they still face some critical challenges (e.g., providing regulation of behaviors and privacy protection of access policy). Motivated by these facts, in this article, we construct a novel secure mutual authentication system, which can be applied in smart homes and other applications. Specifically, the proposed approach integrates blockchain, group signature, and message authentication code to provide reliable auditing of users' access history, anonymously authenticate group members, and efficiently authenticate home gateway, respectively. We also prove the security and privacy requirements, including anonymity, traceability, and confidentiality, that the proposed system satisfies, with an implementation and evaluation to demonstrate its practicality.

With the popularity of edge computing, edge nodes are connected with the Internet of Things (IoT) devices to process and analyze IoT-created data, and feedback corresponding results to users, devices, or data centers. In the edge computing environment, multicast is a typical communication pattern to support data transmitting between edges and devices. It allows the sender to send messages to multiple receivers in one broadcast message. To construct a secure multicast channel, the primary issue is to ensure the privacy and credibility of the transmitted message in the open wireless communication. Then, another essential issue for multicast channels is receiver anonymity, i.e., only the sender knows the receivers' identities. Also, efficiency and provable security are critical in scheme design. In this article, we design a certificateless multimessage and multireceiver signcryption (CLMMSC) scheme by using the elliptic curve cryptography. To facilitate lightweight deployment, we adapt the certificateless mechanism to reduce the system operation and maintenance costs. Then, through security proofs, we demonstrate that the proposed scheme can achieve the expected security properties. The performance analysis shows that the proposed scheme has lower communication costs than previous CLMMSC schemes.

Certificateless public key cryptosystem solves both the complex certificate management problem in the public key cryptosystem based on the PKI and the key escrow issue in the public key cryptosystem based on identity. The aggregator can compress n different signatures with respect to n messages from n signers into an aggregate signature, which can help communication equipments to save a lot of bandwidth and computing resources. Therefore, the certificateless aggregate signature (CLAS) scheme is particularly well suited to address secure routing authentication issues in resource-constrained vehicular ad hoc networks. Unfortunately, most of the existing CLAS schemes have problems with security vulnerabilities or high computation and communication overheads. To avoid the above issues and better solve the secure routing authentication problem in vehicular ad hoc networks, we present a new CLAS scheme and give the formal security proof of our scheme under the CDH assumption in the random oracle model. We then evaluate the performance of our proposed CLAS scheme, and the results demonstrate that our proposal is more practical in resource-constrained vehicular ad hoc networks.

Mobile device and application (app) security are increasingly important, partly due to the constant and fast-paced cyberthreat evolution. To ensure the security of communication (e.g., data-in-transit), a number of identity-based signature schemes have been designed to facilitate authorization identification and validation of messages. However, in many of these schemes, a user's private key may leak when a new signature is generated since the private keys are stored on the device. Seeking to improve the security of the private key, we propose the first two-party distributed signing protocol for the identity-based signature scheme in the IEEE P1363 standard. This protocol requires that two devices separately store one part of the user's private key, and allows these two devices to generate a valid signature without revealing the entire private key of the user. We formally prove that the security of the protocol in the random oracle model. Then, we implement the protocol using the MIRACL library and evaluate the protocol on two mobile devices. Compared with the protocol of Lindell (CRYPTO'17) that uses the zero-knowledge proof for its security, our protocol is more suitable for deployment in the mobile environment.

Natural language processing (NLP) allows a computer program to understand human language as it is spoken, and has been increasingly deployed in a growing number of applications, such as machine translation, sentiment analysis, and electronic voice assistant. While information obtained from different sources can enhance the accuracy of NLP models, there are also privacy implications in the collection of such massive data. Thus, in this paper, we design a privacy-preserving system SecureNLP, focusing on the instance of recurrent neural network (RNN)based sequence-to-sequence with attention model for neural machine translation. Specifically, for non-linear functions such as sigmoid and tanh, we design two efficient distributed protocols using secure multi-party computation (MPC), which are used to carry out the respective tasks in the SecureNLP. We also prove the security of these two protocols (i.e., privacy-preserving long short-term memory network PrivLSTM, and privacy-preserving sequence to sequence transformation PrivSEQ2SEQ) in the semi-honest adversary model, in the sense that any honest-butcurious adversary cannot learn anything else from the messages they receive from other parties. The proposed system is implemented in C++ and Python, and the findings from the evaluation demonstrate the utility of the protocols in cross-domain NLP.

We point out that the key agreement and key protection scheme (published in IEEE Transactions on Information Forensics and Security, doi: 10.1109/TIFS.2018.2850299) fails to achieve the two-factor security. We demonstrate that in the scheme, if an adversary can control the master device of a target user, he can impersonate the user to pass the server's authentication.

Blockchain, a distributed ledger technology, can potentially be deployed in a wide range of applications. Among these applications, decentralized payment systems (e.g. Bitcoin) have been one of the most mature blockchain applications with widespread adoption. While the early designs (e.g. Bitcoin) are often the currency of choice by cybercriminals (e.g., in ransomware incidents), they only provide pseudo-anonymity, in the sense that anyone can deanonymize Bitcoin transactions by using information in the blockchain. To strengthen the privacy protection of decentralized payment systems, a number of solutions such as Monero and Zerocash have been proposed. However, completely Decentralized Anonymous Payment (DAP) systems can be criminally exploited, for example in online extortion and money laundering activities. Recognizing the importance of regulation, we present a novel definition of Decentralized Conditional Anonymous Payment (DCAP) and describe the corresponding security requirements. In order to construct a concrete DCAP system, we first design a Condition Anonymous Payment (CAP) scheme (based on our proposed signature of knowledge), whose security can be demonstrated under the defined formal semantic and security models. To demonstrate utility, we compare the performance of our proposal with that of Zerocash under the same parameters and testing environment.

If all vehicles are connected together through a wireless communication channel, vehicular ad hoc networks (VANETs) can support a wide range of real-time traffic information services, such as intelligent routing, weather monitoring, emergency call, etc. However, the accuracy and credibility of the transmitted messages among the VANETs are of paramount importance as life may depend on it. In this article we introduce a novel framework called blockchain-assisted privacy-preserving authentication system (BPAS) that provides authentication automatically in VANETs and preserves vehicle privacy at the same time. This design is highly efficient and scalable. It does not require any online registration centre (except for system initialization and vehicle registration), and allows conditional tracing and dynamic revocation of misbehaving vehicles. In this article, we conduct an in-depth security analysis and a comprehensive performance evaluation (which is based on the Hyperledger Fabric platform) for our proposed framework. The results demonstrate that our framework is an efficient solution for the development of a decentralized authentication system in VANETs.

Achieving low latency and providing real-time services are two of several key challenges in conventional cloud-based smart grid systems, and hence, there has been an increasing trend of moving to edge computing. While there have been a number of cryptographic protocols designed to facilitate secure communications in smart grid systems, existing protocols generally do not support conditional anonymity and flexible key management. Thus, in this article, we introduce a blockchain-based mutual authentication and key agreement protocol for edge-computing-based smart grid systems. Specifically, leveraging blockchain, the protocol can support efficient conditional anonymity and key management, without the need for other complex cryptographic primitives. The security analysis shows that the protocol achieves reasonable security assurance, and the comparative summary for security and efficiency also suggests the potential of the proposed protocol in a smart grid deployment.

Remote data access control is of crucial importance in public cloud. Based on its own inclinations, the data owner predefines the access policy. When the user satisfies the data owner's access policy, it has the right to access the data owner's remote data. In order to improve flexibility and efficiency of remote data access control, attribute-based encryption (for short, ABE) is used to realize the remote data fine-grained access control. For the low-capacity terminals, verifiable outsourced decryption is a very attractive technique. In the real application scenarios, the user's attributes are usually managed by many authorities. When some authorized users access some sensitive remote data, they hope to preserve their identity privacy. From the two points, we propose an anonymous distributed fine-grained access control protocol with verifiable outsourced decryption in public cloud (for short, VOD-ADAC). VOD-ADAC is a novel concept which is proposed for the first time in the paper. By adopting the pseudonym technique, the user's high anonymity can be achieved by frequently changing the independent pseudonyms at some highly social spots. This paper formalizes the system model and security model of VOD-ADAC protocol. Then, by using hybrid encryption technique of distributed ABE and symmetric encryption, a concrete VOD-ADAC protocol is designed from the bilinear pairings. Through security analysis and performance analysis, our proposed VOD-ADAC protocol is provably secure and efficient.

With the rapid development of cloud services, the resources-constrained enterprises and individuals can outsource the huge sensitive data into the Cloud Service Providers (CSPs) who fully control the data physically. Since CSPs are not fully trusted, it is essential to protect the integrity and confidentiality of users' data. Plenty of researchers have devoted considerable attention to solve this issue in the last decade such as various PDP and POR schemes. In this paper, we propose an algebraic signature-based data integrity auditing scheme that ensures the cloud data integrity and confidentiality with batch auditing. Moreover, one advantage of the scheme is that it can also support data dynamics by using only one cloud server. The security analysis shows that our construction can achieve the desired security properties. We also provide the simulation results of the dynamic operations on different numbers of data blocks and sub-blocks, which show that our scheme is efficient for real-world applications.

The maturity of cloud computing, the Internet of Things technology, and intelligent transportation system has promoted the rapid development of vehicular ad-hoc networks (VANETs). To keep pace with real-world demands (mobility, low latency, etc.) in a practical VANETs deployment, there have been attempts to integrate fog computing with VANETs. To facilitate secure interaction in fog-based VANETs, we design a new authenticated key agreement protocol without bilinear pairing. This protocol achieves mutual authentication, generates a securely agreed session key for secret communication, and supports privacy protection. We also give a strict formal security proof and demonstrate how the proposed protocol meets the security requirements in the fog-based VANETs. We then evaluate the efficiency of the proposed protocol, and it shows the practicality of the protocol.

In vehicle-to-grid (V2G) networks, battery-powered vehicle (BV) provides service to the power grid. In order to encourage more BVs to provide the service for power grid, it is necessary to reward the BVs from the power grid. To extensively deploy V2G networks, some security and privacy problems must be solved. In this paper, for the first time, we propose the novel concept of blockchain-based anonymous rewarding scheme (BBARS) for V2G networks. The novel concept comes from the application requirement which has not been solved by now. We give the formal system model and security model of BBARS. Then, we design the concrete BBARS scheme by making use of two different public key cryptosystem. Through security analysis and performance analysis, the designed scheme is provably secure and efficient. The analysis results also show the designed BBARS scheme is practical for secure V2G networks in smart grid.

As an important part of smart cities, vehicle ad hoc networks (VANETs) have attracted much attention from both industry and academia. In a VANET, generating a secure session key to facilitate subsequent data-in-transit transfer between two or more vehicles is crucial, which can be achieved by using an authenticated key agreement protocol. However, most of the existing identity-based two-party authenticated key agreement protocols have significant computational requirements or are known to be insecure. Thus, in this paper, a secure and efficient identity-based two-party authenticated key agreement protocol is presented by us. This protocol does not involve complex bilinear pairing computations and can generate a valid session key in two rounds. The security of the proposed protocol is proved in the eCK model which has better capability to describe a protocol’s security than the famous CK model, and it has been widely used in the security proof of ID-based key agreement protocols currently. Additionally, we also evaluate its performance for potential utility in a VANET.

Smart grid has emerged as the next-generation electricity grid with power flow optimization and high power quality. Smart grid technologies have attracted the attention of industry and academia in the last few years. However, the tradeoff between security and efficiency remains a challenge in the practical deployment of the smart grid. Most recently, Li et al. proposed a lightweight message authentication scheme with user anonymity and claimed that their scheme is provably secure. But we found that their scheme fails to achieve mutual authentication and mitigate some typical attacks (e.g., impersonation attack, denial of service attack) in the smart grid environment. To address these drawbacks, we present a new message authentication scheme with reasonable efficiency. Security and performance analysis results show that the proposed scheme can satisfy the security and lightweight requirements of practical implementations and deployments of the smart grid.

Data sharing in cloud computing enables multiple participants to freely share the group data, which improves the efficiency of work in cooperative environments and has widespread potential applications. However, how to ensure the security of data sharing within a group and how to efficiently share the outsourced data in a group manner are formidable challenges. Note that key agreement protocols have played a very important role in secure and efficient group data sharing in cloud computing. In this paper, by taking advantage of the symmetric balanced incomplete block design (SBIBD), we present a novel block design-based key agreement protocol that supports multiple participants, which can flexibly extend the number of participants in a cloud environment according to the structure of the block design. Based on the proposed group data sharing model, we present general formulas for generating the common conference key IC for multiple participants. Note that by benefiting from the (v, k + 1, 1)-block design, the computational complexity of the proposed protocol linearly increases with the number of participants and the communication complexity is greatly reduced. In addition, the fault tolerance property of our protocol enables the group data sharing in cloud computing to withstand different key attacks, which is similar to Yi's protocol.

As mobile devices ownership becomes more prevalent (e.g., a user owns multiple mobile devices), the capability to offer secure and user friendly authentication becomes increasingly important. A large number of identity-based user authentication mechanisms for the wireless mobile environment have been proposed. However, they are not generally designed for situations where a user's private key and some other sensitive data can be exposed if his/her mobile device is remotely or physically controlled by an attacker. Threshold secret sharing is one of the solutions to this problem, but it is limited in the requirement that there should exist an honest third-party to hold the complete key after the secret reconstruction process. Therefore, in this paper, we consider the special case that only two devices (i.e., no honest party) at the user's side jointly perform user authentication with a server, and neither device can successfully complete the authentication process alone. Moreover, the key reconstruction is not needed during authentication so that neither device can hold a complete key. We then analyze the security of the proposed protocol and show that it satisfies all known security requirements in practical applications, particularly the key exposure attack resistance. The performance analysis of the proposed protocol is also presented to demonstrate its practicality.

When the data is stored in public clouds, provable data possession (for short, PDP) is of crucial importance in cloud storage. PDP can make the users verify whether their outsourced data is kept intact without downloading the whole data. In some application scenarios, anonymity is very important in order to protect the user identity privacy. In order to encourage users to disclose bad event, the government or organization or individual may pay for the user who provides the precious data. Thus, incentive and unconditionally anonymous identity-based public PDP (for short, IAID-PDP) is a very important security concept. From the above requirements, for the first time, we propose the concept of IAID-PDP. We formalize its system model and security model. Based on the bilinear pairings, a concrete IAID-PDP protocol is presented. Based on the standard hard problems, the proposed IAID-PDP protocol is provably secure. IAID-PDP protocol eliminates the complex certificate management since it is designed in the identity-based public key cryptography. Through the performance analysis and security analysis, our IAID-PDP protocol satisfies the following properties: certification elimination, incentive, unconditional anonymity and remote data integrity checking.

Rapid advances in wireless communications, hardware/software, and Internet technologies have contributed to an exponential growth in the number of users accessing the Internet using mobile, wearable or other Internet of Things devices. Identity-based signature schemes have been widely applied to enforce user authorization and validate user messages in mobile wireless networks. However, the user’s private key used to generate signatures is prone to leakage because the key is being stored on the mobile device. Several (t, n) threshold secret sharing schemes have been proposed to address the issue. One limitation is that the private keys in most of those schemes have to be recovered on a single device when generating signatures, so that the user who holds the device can sign any message without the participation of other users. To address the recovery limitation, we propose an efficient and secure two-party distributed signing protocol for the identity-based signature scheme in the IEEE P1363 Standard, where two users can generate a valid signature without recovering the whole private key. We formally prove its security under a nonstandard assumption. We also implemented our proposed protocol using the MIRACL Cryptographic software development kit. The experimental results obtained show that the time it takes for two general Android devices to generate a signature is about 709.53 ms.

Electronic prescription is increasingly popular in our society, particularly in technologically advanced countries. Due to strict legal requirements and privacy regulations, authorization and data confidentiality are two important features in electronic prescription system. By combining signature and encryption functions, signcryption is an efficient cryptographic primitive that can be used to provide these two features. While signcryption is a fairly established research area, most signcryption schemes proposed recently have several limitations (e.g., high communication costs, limited bandwidth, and insecurity), and designing secure and practical signcryption schemes remains challenging. In this paper, we propose an improved certificateless proxy signcryption (CLPSC) scheme, based on elliptic curve cryptography (ECC). We also demonstrate that the proposed CLPSC scheme is secure in the random oracle model and evaluate its performance with related schemes. The security and performance evaluations show that the proposed CLPSC scheme can potentially be implemented on resource-constrained low-computing mobile devices in an electronic prescription system.

With the application of sensor technology in the field of healthcare, online data sharing in healthcare industry attracts more and more attention since it has many advantages, such as high efficiency, low latency, breaking the geographical location, and time constraints. However, due to the direct involvement of patient health information, the privacy and integrity of medical data have become a matter of much concern to the healthcare industry. To retain data privacy and integrity, a number of digital signature schemes have been introduced in recent years. Unfortunately, most of them suffer serious security attacks and do not perform well in terms of computation overhead and communication overhead. Very recently, Pankaj Kumar et al. proposed a certificateless aggregate signature scheme for healthcare wireless sensor network. They claimed that their signature scheme was able to withstand a variety of attacks. However, in this paper, we find that their scheme fails to achieve its purpose since it is vulnerable to signature forgery attack and give the detailed attack process. Then, we propose a new certificateless aggregate signature scheme to fix the security flaws and formally prove that our proposed scheme is secure under the computationally hard Diffie-Hellman assumption. Security analysis and performance evaluation demonstrate that the security of our proposal is improved while reducing the computation cost. Compared with Pankaj Kumar et al.'s scheme, our proposed scheme is more efficient and suitable for the healthcare wireless sensor networks (HWSNs) to maintain security at various levels.

In a typical single-server architecture, when a user wishes to access multiple servers to obtain different services, the user needs to register with every single server. This results in multiple identities and password pairs. To eliminate the limitation of the user having to possess and remember multiple identities and password pairs, a number of multiserver authentication protocols have been proposed where a user only needs to register once. However, most existing protocols are subsequently found to be insecure and this topic remains one of the ongoing research interests. Thus, in this paper, we present a multiserver authentication key agreement protocol. We then demonstrate the security of the protocol under the random oracle model, as well as the practicality of the protocol in terms of low computation and communication costs, minimal storage requirements, and operation costs.

With rapid developments of sensor, wireless and mobile communication technologies, Mobile Healthcare Social Networks (MHSNs) have emerged as a popular means of communication in healthcare services. Within MHSNs, patients can use their mobile devices to securely share their experiences, broaden their understanding of the illness or symptoms, form a supportive network, and transmit information (e.g., state of health and new symptoms) between users and other stake holders (e.g., medical center). Despite the benefits afforded by MHSNs, there are underlying security and privacy issues (e.g., due to the transmission of messages via a wireless channel). The handshake scheme is an important cryptographic mechanism, which can provide secure communication in MHSNs (e.g., anonymity and mutual authentication between users, such as patients). In this paper, we present a new framework for the handshake scheme in MHSNs, which is based on hierarchical identity-based cryptography. We then construct an efficient Cross-Domain HandShake (CDHS) scheme that allows symptoms-matching within MHSNs. For example, using the proposed CDHS scheme, two patients registered with different healthcare centers can achieve mutual authentication and generate a session key for future secure communications. We then prove the security of the scheme, and a comparative summary demonstrates that the proposed CDHS scheme requires fewer computation and lower communication costs. We also implement the proposed CDHS scheme and three related schemes in a proof of concept Android app to demonstrate utility of the scheme. Findings from the evaluations demonstrate that the proposed CDHS scheme achieves a reduction of 18.14 and 5.41 percent in computation cost and communication cost, in comparison to three other related handshake schemes.

The smart grid is considered to be the next-generation power system because of its reliability, efficiency, and cost-effectiveness. In recent years, the smart grid technology has attracted a lot of attention from both academia and industry. Advances in smart grid technologies are enabling more data to be collected and analyzed in real-time for many kinds of smart grid applications. As the amount of data increases, the traditional smart grid data management system cannot provide sufficient storage and processing capacities. To address these challenges, cloud computing is being introduced into the power system and the cloud-based smart grid data management system has been proposed to better support smart grid applications. In this cloud-based system, the data are stored and analyzed by the remote cloud server according to the requirements of smart grid applications. However, the loss of physical control over the smart grid data makes it a significant challenge in ensuring the integrity of the data. Many provable data possession schemes have been proposed in the past few years. However, most of them suffer from serious security weaknesses or poor performance. We propose an efficient certificateless provable data possession (CL-PDP) scheme for cloud-based smart grid applications. Security analysis shows that the proposed scheme is provably secure in a robust security model and can satisfy several security requirements. Performance analysis demonstrates that the proposed scheme results in lower computation costs as compared to two recently proposed CL-PDP schemes.

Industrial Internet of Things (IIoT) integrates various types of intelligent terminals, mobile devices, and communication technologies to enable the upgrade of traditional industries to intelligent industries. IIoT relies on the powerful data processing capabilities of cloud computing to reduce the cost of various on-demand services as per the requirements of users. However, the privacy and confidentiality of the outsourced data should be protected in this environment because the data are typically “handled” by a third-party service provider. An encryption technique can guarantee the confidentiality of the data but it limits data retrieval due to its innate “all-or-nothing” decryption feature. To apply encryption to privacy-preserving data retrieval, many public key encryption techniques with keyword search systems have been proposed in the literature. However, most of the existing schemes are vulnerable to inside keyword guessing attack (IKGA), which is caused by a small keyword space. To address this problem, we propose a certificateless public key authenticated encryption with keyword search scheme, which is provably secure against IKGA. A performance analysis of the proposed scheme demonstrates that it is more secure and effective compared with other certificateless public key encryption with keyword search schemes.

With the widespread adoption of Internet of Things and cloud computing in different industry sectors, an increasing number of individuals or organizations are outsourcing their Industrial Internet of Things (IIoT) data in the cloud server to achieve cost saving and collaboration (e.g., data sharing). However, in this environment, preserving the privacy of data remains a key challenge and inhibiting factor to an even wider adoption of IIoT in the cloud environment. To mitigate these issues, in this paper, we design a new secure channel-free certificateless searchable public key encryption with multiple keywords scheme for IIoT deployment. We then demonstrate the security of the scheme in the random oracle model against two types of adversaries, where one adversary is given the power to choose a random public key instead of any user's public key and another adversary is allowed to learn the system master key. In the presence of these types of adversaries, we evaluate the performance of the proposed scheme and demonstrate that it achieves (computational) efficiency with low communication cost.

To support a sustainable development of smart city, smart grid is an indispensable part. Sensor technology in smart gird enables interactive real-time data transmission between cloud and the edge of the network. There are a number of research challenges in the design of smart grids. One of these research challenges is balancing customer privacy and the cloud-based power system's function optimization. Identity-based encryption with equality test (IBEET) scheme has recently been identified as a viable solution, in which customers can delegate a trapdoor to the power system control server and the server then searches on the encrypted data to determine whether two different ciphertexts are encryptions of the same plaintext. Unfortunately, existing schemes are inefficient and the trapdoor could be used to perform equality test on any message; thus, leakage of privacy. In this paper, we propose an efficient IBEET scheme with bilinear pairing, which reduces the need for time-consuming HashToPoint function and each trapdoor could only be used to perform the equality test on a particular keyword. We then prove the security of our scheme for one-way chosen-ciphertext security against a chosen identity (OW-ID-CCA) attack in the random oracle model (ROM). The performance evaluation of our scheme demonstrates that in comparison to the scheme of Ma (2016), our scheme achieves a reduction of 36.7 and 39.24 percent in computation costs during the encryption phase and test phase, respectively.

Internet of Things (IoT) and cloud computing are increasingly integrated, in the sense that data collected from IoT devices (generally with limited computational and storage resources) are being sent to the cloud for processing, etc., in order to inform decision making and facilitate other operational and business activities. However, the cloud may not be a fully trusted entity, like leaking user data or compromising user privacy. Thus, we propose a privacy‐preserving and user‐controlled data sharing architecture with fine‐grained access control, based on the blockchain model and attribute‐based cryptosystem. Also, the consensus algorithm in our system is the Byzantine fault tolerance mechanism, rather than Proof of Work.

Sensitive data stored in laptops or other mobile devices can easily be lost, stolen, misplaced or corrupted, the remote backup storage technique is used to address these issues; however, the backup server could not be fully trusted, the data should be encrypted in advance. Although the key is more easily protected due to the smaller size compared with the backup data, it is still impossible for ordinary human to remember. A user‐centred design data backup scheme is proposed using multi‐factor authentication. The user firstly selects a symmetrical key and divides it into three shares, then destroys the key. The key can easily be reconstructed by combining the shares stored in the user's smart card and the laptop. Even if the smart card or laptop is lost, the key can still be recovered with the password and biometrics. The proposed scheme not only achieves the required security goals but also is more robust and practical.

Along with the development of information technology, the traditional electrical grid is moving to smart grid technology. By using the smart grid, the users and utility providers can more efficiently manage and generate power. Along with the advantages, the smart grid is also faced with new security concerns. In the smart grid, the user's citizen identity information should be preserved and the offensive user should be traced. For some low‐capacity devices, it is indispensable to perform complicated computation by using outsourcing computation. The authors provide the outsourcing computation through public cloud. Anonymity and traceability are two important security properties in the smart grid. They are the unity of opposites. On the basis of the security requirements, they propose the balanced anonymity and traceability for outsourcing small‐scale data linear aggregation (BAT‐LA) in the smart grid. The formal definition, system model and security model are presented. Then, a concrete BAT‐LA protocol is designed by using the elliptic curve cryptography and proxy re‐encryption. Through security analysis and performance analysis, the designed BAT‐LA protocol is provably secure and efficient.

Public verification of data integrity is crucial for promoting the serviceability of cloud storage systems. Recently, Tan and Jia (2014) proposed an identity-based public verification (NaEPASC) protocol for cloud data to simplify key management and alleviate the burden of check tasks. They claimed that NaEPASC enables a third-party auditor (TPA) to verify the integrity of outsourced data with high efficiency and security in a cloud computing environment. However, in this paper, we pinpoint that NaEPASC is vulnerable to the signature forgery attack in the setup phase; i.e., a malicious cloud server can forge a valid signature for an arbitrary data block by using two correct signatures. Moreover, we demonstrate that NaEPASC is subject to data privacy threats in the challenge phase; i.e., an external attacker acting as a TPA can reveal the content of outsourced data. The analysis shows that NaEPASC is not secure in the data verification process. Therefore, our work is helpful for cryptographers and engineers to design and implement more secure and efficient identity-based public auditing schemes for cloud storage.

The automatic-dependent surveillance-broad-cast (ADS-B) is generally regarded as the most important module in air traffic surveillance technology. To obtain better airline security, ADS-B system will be deployed in most airspace by 2020, where aircraft will be equipped with an ADS-B device that periodically broadcasts messages to other aircraft and ground station controllers. Due to the open communication environment, the ADS-B system is subject to a broad range of attacks. To simultaneously implement both integrity and authenticity of messages transmitted in the ADS-B system, Yang et al. proposed a new authentication frame based on the three-level hierarchical identity-based signature (TLHIBS) scheme with batch verification, as well as constructing two schemes for the ADS-B system. However, neither TLHIBS schemes are sufficiently lightweight for practical deployment due to the need for complex hash-to-point operation or expensive certification management. In this paper, we construct an efficient TLHIBS scheme with batch verification for the ADS-B system. Our scheme does not require hash-to-point operation or (expensive) certification management. We then prove the TLHIBS scheme secure in the random oracle model. We also demonstrate the practicality of the scheme using experiments, whose findings indicate that the TLHIBS scheme supports attributes required by the ADS-B system without the computation cost in Chow et al.'s scheme and Yang et al.'s TLHIBS schemes.

Recent advances of Internet and microelectronics technologies have led to the concept of smart grid which has been a widespread concern for industry, governments, and academia. The openness of communications in the smart grid environment makes the system vulnerable to different types of attacks. The implementation of secure communication and the protection of consumers’ privacy have become challenging issues. The data aggregation scheme is an important technique for preserving consumers’ privacy because it can stop the leakage of a specific consumer’s data. To satisfy the security requirements of practical applications, a lot of data aggregation schemes were presented over the last several years. However, most of them suffer from security weaknesses or have poor performances. To reduce computation cost and achieve better security, we construct a lightweight data aggregation scheme against internal attackers in the smart grid environment using Elliptic Curve Cryptography (ECC). Security analysis of our proposed approach shows that it is provably secure and can provide confidentiality, authentication, and integrity. Performance analysis of the proposed scheme demonstrates that both computation and communication costs of the proposed scheme are much lower than the three previous schemes. As a result of these aforementioned benefits, the proposed lightweight data aggregation scheme is more practical for deployment in the smart grid environment.

To provide timely feedbacks to users, nearly every respectable Internet service now imposes a password strength meter (PSM) upon user registration or password change. It is a rare bit of good news in password research that well-designed PSMs do help improve the strength of user-chosen passwords. However, leading PSMs in the industrial world (e.g., Zxcvbn, KeePSM and NIST PSM) are mainly composed of simple heuristic rules and found to be highly inaccurate, while state-of-the-art PSMs from academia (e.g., probabilistic context-free grammar based ones and Markov-based ones) are still far from satisfactory, especially incompetent at gauging weak passwords. As preventing weak passwords is the primary goal of any PSM, this means that existing PSMs largely fail to serve their purpose. To fill this gap, in this paper we propose a novel PSM that is grounded on real user behavior. Our user survey reveals that when choosing passwords for a new web service, most users (77.38%) simply retrieve one of their existing passwords from memory and then reuse (or slightly modify) it. This is in vast contrast to the seemingly intuitive yet unrealistic assumption (often implicitly) made in most of the existing PSMs that, when user registers, a whole new password is constructed by mixing segments of letter, digit and/or symbol or by combining n-grams. To model users' realistic behaviors, we use passwords leaked from a less sensitiveservice as our base dictionary and another list of relatively strong passwords leaked from a sensitive service as our training dictionary, and determine how mangling rules are employed by users to construct passwords for new services. This process automatically creates a fuzzy probabilistic context-free grammar (PCFG) and gives rise to our fuzzy-PCFG-based meter, fuzzyPSM. It can react dynamically to changes in how users choose passwords and is evaluated by comparisons with five representative PSMs. Extensive experiments on 11 real-world password lists show that fuzzyPSM, in general, outperforms all its counterparts, especially accurate in telling apart weak passwords and suitable for services where online guessing attacks prevail.

Due to efficiency, security and reliability, the smart grid attracts more and more attentions from both industry and researchers. To implement secure communication in the smart grid, how to distribute secret keys among participants become an important issue. Several key distribution schemes for the smart grid have been proposed to guarantee secure communication. However, most of them cannot provide smart meter anonymity or have unsatisfactory performance. Based on the identity‐based cryptography, this study proposes an anonymous key distribution (AKD) scheme for the smart grid using the elliptic curve cryptography. The proposed AKD scheme can provide the smart meter anonymity and mutual authentication between two participants without any help of the trusted anchor. Due to the fact that no bilinear paring operation is involved in the execution, the proposed AKD scheme has much better performance than the latest AKD scheme proposed by Tsai and Lo. Detailed performance analysis shows that the computation and the communication costs of the authors’ AKD scheme is about 82.39 and 52.33% less than that of Tsai and Lo's AKD scheme. Besides, security analysis shows that the proposed AKD scheme is provably secure in the random oracle model.

Abstract Recently, Chen et al. proposed a certificateless aggregate signature scheme with efficient verification. They claimed that their scheme could resist attacks of Type I adversary and Type II adversary. Unfortunately, we present a universal attack to demonstrate that their scheme cannot provide unforgeability. The adversary in the proposed attack can forge a legal signature on any message without any users' secret information. Copyright © 2016 John Wiley & Sons, Ltd.

Covert channel is a major threat to the information system security and commonly found in operating systems, especially in cloud computing environment. Owing to the characteristics in cloud computing environment such as resources sharing and logic boundaries, covert channels become more varied and difficult to find. Focusing on those problems, this paper presents a universal method for detecting covert channel automatically. To achieve a global detection, we leveraged a virtual machine event record mechanism in hypervisor to gather necessary metadata. Combining the shared resources matrix methodology with events association mechanism, we proposed a distinctive algorithm that can accurately locate and analyze malicious covert channels from the respect of behaviors. Compared with the popular statistical test methods focusing on the single covert channel, our method is capable of recognizing and detecting more covert channels in real time. Experimental results show that this method is not only able to detect multilevel and multiform covert channels in cloud environment effectively but also facilitates the implementation and deployment in practical scenarios without modifying the existing system. Copyright © 2016 John Wiley & Sons, Ltd.

With the dramatic development of cloud computing, more and more challenges emerge for storing massive amounts of data. Data repairing is a main technique to provide data availability in the distributed storage system, such as cloud platform, once storage corruption occurs. In cloud storage, the redundant data are commonly stored in different places for better capability of disaster recovery and are transferred through the open channel, such as Internet. Because the data are of great importance for organizations, it is essential to systematically preserve the confidentiality, integrity, and authenticity of the data, which counters threats such as wiretapping, tampering, and pollution attacks. To address these challenges, we put forward a new data repairing paradigm, referred to as efficient and secure data repairing ESDR paradigm. In ESDR, the components of the redundant data are distributed to other storage units after being preprocessed and can be collected and reassembled onto the corrupted unit. Following this paradigm, we propose an ESDR scheme by using regenerating code and certificateless signcryption technique. Furthermore, the proposed enc2-mac - signcrypt preprocessing promotes security and efficiency notably. Both theoretical analysis and experimental evaluation confirm that this scheme is practical and efficient to secure data repairing in cloud storage. Copyright © 2016 John Wiley & Sons, Ltd.

Rapid advances in wireless communication technologies have paved the way for a wide range of mobile devices to become increasingly ubiquitous and popular. Mobile devices enable anytime, anywhere access to the Internet. The fast growth of many types of mobile services used by various users has made the traditional single-server architecture inefficient in terms of its functional requirements. To ensure the availability of various mobile services, there is a need to deploy multi-server architectures. To ensure the security of various mobile service applications, the anonymous mobile user authentication (AMUA) protocol without online registration using the self-certified public key cryptography (SCPKC) for multi-server architectures was proposed in the past. However, most of the past AMUA solutions suffer from malicious attacks or have unacceptable computation and communication costs. To address these drawbacks, we propose a new AMUA protocol that uses the SCPKC for multi-server architectures. In contrast to the existing AMUA protocols, our proposed AMUA protocol incurs lower computation and communication costs. By comparing with two of the latest AMUA protocols, the computation and the communication costs of our protocol are at least 74.93% and 37.43% lower than them, respectively. Moreover, the security analysis of our AMUA protocol demonstrates that it satisfies the security requirements in practical applications and is provably secure in the novel security model. By maintaining security at various levels, our AMUA protocol is more practical for various mobile applications.

More and more clients would like to store their data to public cloud servers (PCSs) along with the rapid development of cloud computing. New security problems have to be solved in order to help more clients process their data in public cloud. When the client is restricted to access PCS, he will delegate its proxy to process his data and upload them. On the other hand, remote data integrity checking is also an important security problem in public cloud storage. It makes the clients check whether their outsourced data are kept intact without downloading the whole data. From the security problems, we propose a novel proxy-oriented data uploading and remote data integrity checking model in identity-based public key cryptography: identity-based proxy-oriented data uploading and remote data integrity checking in public cloud (ID-PUIC). We give the formal definition, system model, and security model. Then, a concrete ID-PUIC protocol is designed using the bilinear pairings. The proposed ID-PUIC protocol is provably secure based on the hardness of computational Diffie-Hellman problem. Our ID-PUIC protocol is also efficient and flexible. Based on the original client's authorization, the proposed ID-PUIC protocol can realize private remote data integrity checking, delegated remote data integrity checking, and public remote data integrity checking.

Recently, Gu et al. proposed an efficient identity-based proxy signature scheme and demonstrated their scheme was provably secure in the standard model. In this paper, we show their scheme is not secure against the malicious user through proposing three concrete attacks.

Advances in information and communication technologies have led to the emergence of Internet of Things (IoT). In the healthcare environment, the use of IoT technologies brings convenience to physicians and patients as they can be applied to various medical areas (such as constant real-time monitoring, patient information management, medical emergency management, blood information management, and health management). The radio-frequency identification (RFID) technology is one of the core technologies of IoT deployments in the healthcare environment. To satisfy the various security requirements of RFID technology in IoT, many RFID authentication schemes have been proposed in the past decade. Recently, elliptic curve cryptography (ECC)-based RFID authentication schemes have attracted a lot of attention and have been used in the healthcare environment. In this paper, we discuss the security requirements of RFID authentication schemes, and in particular, we present a review of ECC-based RFID authentication schemes in terms of performance and security. Although most of them cannot satisfy all security requirements and have satisfactory performance, we found that there are three recently proposed ECC-based authentication schemes suitable for the healthcare environment in terms of their performance and security.

Despite two decades of intensive research, it remains a challenge to design a practical anonymous two-factor authentication scheme, for the designers are confronted with an impressive list of security requirements (e.g., resistance to smart card loss attack) and desirable attributes (e.g., local password update). Numerous solutions have been proposed, yet most of them are shortly found either unable to satisfy some critical security requirements or short of a few important features. To overcome this unsatisfactory situation, researchers often work around it in hopes of a new proposal (but no one has succeeded so far), while paying little attention to the fundamental question: whether or not there are inherent limitations that prevent us from designing an “ideal” scheme that satisfies all the desirable goals? In this work, we aim to provide a definite answer to this question. We first revisit two foremost proposals, i.e. Tsai et al.'s scheme and Li's scheme, revealing some subtleties and challenges in designing such schemes. Then, we systematically explore the inherent conflicts and unavoidable trade-offs among the design criteria. Our results indicate that, under the current widely accepted adversarial model, certain goals are beyond attainment. This also suggests a negative answer to the open problem left by Huang et al. in 2014. To the best of knowledge, the present study makes the first step towards understanding the underlying evaluation metric for anonymous two-factor authentication, which we believe will facilitate better design of anonymous two-factor protocols that offer acceptable trade-offs among usability, security and privacy.

By broadcasting messages about traffic status to vehicles wirelessly, a vehicular ad hoc network (VANET) can improve traffic safety and efficiency. To guarantee secure communication in VANETs, security and privacy issues must be addressed before their deployment. The conditional privacy-preserving authentication (CPPA) scheme is suitable for solving security and privacy-preserving problems in VANETs, because it supports both mutual authentication and privacy protection simultaneously. Many identity-based CPPA schemes for VANETs using bilinear pairings have been proposed over the last few years to enhance security or to improve performance. However, it is well known that the bilinear pairing operation is one of the most complex operations in modern cryptography. To achieve better performance and reduce computational complexity of information processing in VANET, the design of a CPPA scheme for the VANET environment that does not use bilinear paring becomes a challenge. To address this challenge, we propose a CPPA scheme for VANETs that does not use bilinear paring and we demonstrate that it could supports both the mutual authentication and the privacy protection simultaneously. Our proposed CPPA scheme retains most of the benefits obtained with the previously proposed CPPA schemes. Moreover, the proposed CPPA scheme yields a better performance in terms of computation cost and communication cost making it be suitable for use by the VANET safety-related applications.

The certificateless public key cryptography has attracted wide attention since it could solve the certificate management problem in the traditional public key cryptography and the key escrow problem in the identity‐based public key cryptography. Recently, several certificateless short signature schemes, which could satisfy the requirement of low‐bandwidth communication environments, have been proposed. However, most of them are not secure against either the Type I adversary or the Type II adversary. In this study, the authors propose a new efficient certificateless short signature scheme. The analysis shows the authors' scheme has better performance than the related schemes and is secure against both of the super Type I and the super Type II adversaries.

ABSTRACT The session initiation protocol (SIP) is one of the most important protocols supporting multimedia services. With the wide spread of the internet, the security of SIP is becoming more and more important. In 2009, Tsai proposed an efficient authentication scheme as an enhancement to SIP. However, Arshad et al. demonstrated that Tsai's scheme was vulnerable to the off‐line password‐guessing attack and the stolen‐verifier attack. They also pointed out that Tsai's scheme did not provide known‐key secrecy and perfect forward secrecy. To overcome the weaknesses, Arshad et al. also proposed an improved authentication scheme based on the elliptic curve discrete logarithm problem for SIP and claimed that their scheme can withstand various attacks. In this paper, we do a cryptanalysis of the scheme by Arshad et al., and we show that their scheme is vulnerable to the off‐line password‐guessing attack. We also propose an improved authentication scheme based on the elliptic curve cryptography for SIP which is immune to the presented attacks. Copyright © 2012 John Wiley & Sons, Ltd.

ABSTRACT With the popularity of Internet and wireless networks, more and more network architectures are used in multi‐server environment, in which users remotely access servers through open networks. For the reliability of accessing these remote services, user must pass a verification procedure to obtain the authorization for legal resource acquisition and data exchange. Recently, several dynamic identity‐based authentication protocols for multi‐server environment have been proposed, but all of these protocols have been cryptanalyzed by other scholars. In this paper, we propose a new dynamic identity‐based authentication protocol for multi‐server environment using elliptic curve cryptography. The analysis shows that our protocol could overcome security weaknesses in the previously published protocols. Hence, our protocol is more suitable for practical applications. Copyright © 2012 John Wiley & Sons, Ltd.