ABSTRACT Transitive signatures are a special type of homomorphic signature proposed by Turing Award winners Micali and Rivest, which are highly suitable for authenticating dynamically growing graph‐based data systems. In such a signature scheme, anyone with the signer's public key is allowed to generate a signature for a composed edge , from two signatures on adjacent edges and . To prevent the problem of malicious dissemination of signatures by verifiers leading to data privacy leakage, researchers have proposed a series of universal designated verifier transitive signature (UDVTS) schemes. However, existing work requires that the designated verifier create its own secret‐public key pair using the public key parameters provided by the signer. Besides, these schemes suffer from significant performance defects due to expensive pairing or exponentiation operations. In this work, we design a pairing‐free and exponentiation‐free UDVTS proof scheme based on the SM2 digital signature algorithm and a zero‐knowledge proof scheme. We prove the security of our construction based on rigorous cryptographic assumptions. The performance comparison with related work shows that our UDVTS proof scheme has an optimal computational cost and desirable communication cost. For example, compared to the state‐of‐the‐art work, we reduce the signing cost by and the designated verification cost by .

The sharing of electronic medical records (EMRs) significantly enhances disease research and healthcare system efficiency. However, outsourcing EMRs to cloud servers introduces risks such as tampering and malicious propagation by recipients. Existing solutions combining blockchain and universal designated verifier signature proofs (UDVSPs) mitigate these risks but rely on secure channels for key sharing, adding communication and computation costs that hinder deployment. In this article, we introduce the first secure channel-free universal designated verifier signature proofs (SCF-UDVSPs) scheme, leveraging simplified cryptographic techniques like the$\Sigma $-protocol and public key encryption. Integrating SCF-UDVSP with blockchain, we develop an optimized EMR sharing system that effectively prevents these attacks, including tampering and malicious propagation. Security proofs and performance analysis validate the feasibility and effectiveness of our proposed system. Compared to existing UDVSP solutions, our approach reduces computational costs by approximately 59.3% without increasing communication overhead, while also eliminating the need for establishing a secure channel.

Zero Trust networks provide an innovative cybersecurity architecture that effectively incorporates “never trust, always verify" principles to address traditional network security threats. Universal Designated Verifier Signature (UDVS) can protect the clients’ privacy in Zero Trust networks, preventing malicious gateways from leaking clients access information to third parties. However, existing UDVS schemes suffer from computational overhead due to their reliance on bilinear pairing operations. This paper primarily focuses on the general transformation method from Identity-Based Key Encapsulation Mechanism (ID-KEM) to UDVS proposed by Steinfeld et al. We first propose ID-KEM based on the SM2 algorithm and prove that it satisfies the EK and Separable properties required by the transformation. Then, we obtain the first UDVS scheme without bilinear pairing through transformation. In terms of performance analysis, the computational overhead of our scheme is 144.36 milliseconds, which is at least 74.39% lower than the previous UDVS schemes. The communication cost is 96 bytes, which is at least 88.89% lower than other schemes, including the first UDVSP scheme without bilinear pairing. To show the utility of our UDVS scheme, we finally apply it into a Zero Trust-based Software Defined Perimeter (SDP) environment, which reaps privacy-preserving authentication for single packet authorization.

An attribute-based credential (ABC) system allows a user, obtaining a credential on a set of attributes from an issuer, to anonymously prove a subset of attributes to a service provider. Nowadays, delegation is an important requirement of ABC, which allows a user to delegate his credentials to other users. However, traditional delegatable ABC systems only support delegating a credential with all attributes. In many scenarios, an appropriate delegation is a user can delegate his credential on parts of attributes to others. Another requirement is revocation of credentials in case of unexpected events. In this article, we propose a delegatable and revocable attribute-based credential, which simultaneously achieves: (1) a user can delegate a credential on parts of attributes to other entities (devices/users); (2) a user can efficiently revoke his credentials or those delegated by him; (3) a user can selectively disclose some attributes and also can prove that the non-disclosed attributes satisfy some relations. To achieve our delegatable and revocable attribute-based credential, we introduce a new primitive, called purgeable signature (PS). We formally define the security model of PS. We then give an efficient construction with a constant-size signature and present the security proofs of PS. Finally, the experimental results show the efficiency of our system.

Conditional privacy-preserving authentication (CPPA) has been widely studied to ensure authentication, anonymity, and traceability in vehicle ad hoc networks (VANETs). Among CPPA schemes, certificateless CPPA (CL-CPPA) offers natural advantages for VANETs by avoiding the complex certificate management of PKI-based solutions and the key escrow problem of identity-based systems. However, many existing CL-CPPA schemes overlook secure message communication. When confidentiality is required, they often rely on additional encryption, which adds communication overhead comparable to that of certificate transmission in PKI-based solutions. Anamorphic signatures (proposed at CRYPTO'23) can be adopted to address this issue by embedding sensitive messages within signatures, which eliminates the need for separate encryption. However, existing anamorphic signature schemes are symmetric, requiring extensive key agreements between two entities, which is impractical for the dynamic nature of VANETs. In this paper, we introduce a new cryptographic primitive, asymmetric anamorphic signatures (AAS), which enables secure message sharing in a public-key setting, thus eliminating the need for complex key agreements. We also provide a concrete construction of AAS based on a variant of the Hohenberger-Waters signature scheme. By integrating AAS with CL-CPPA, we proposeSphinx, a scheme that ensures authentication, anonymity, traceability, and confidentiality without the overhead of additional secure transmissions or complex key agreements. Our security proofs and performance evaluations demonstrate the practicality and efficiency ofSphinx, particularly its advantage in reducing communication overhead.

Privacy concerns have been persistently afflicting individuals within online social networks (OSNs), rendering privacy-preserving communications over the Internet with authentication especially important. Unfortunately, the guarantees of privacy and authenticity are not always provided in OSNs. Individuals are still facing the challenges of being deceived or exploited. To mitigate these issues, anonymous social networks (ASNs) have emerged as a remedy for OSNs, facilitating individuals to connect with others anonymously and authentically. Despite the existence of numerous and remarkable cryptographic primitives, there are no formal solutions for ASNs except for matchmaking encryption (ME), since ME can simultaneously provide various key functionalities, i.e. bilateral access control, identity anonymity, and message authentication, to address the requirements of ASNs. In this paper, we design a system for ASNs by adopting fuzzy identity-based matchmaking encryption (fuzzy IB-ME), and the proposed scheme in this work is highly efficient. The scheme also realizes adaptive security in generic group model (GGM), which is generally adopted in pairing-based cryptography. The proposed ASNs system offers various advantages compared to the previous solutions, including 1) bilateral access control, 2) enhanced security, 3) high scalability, and 4) high efficiency. In addition to theoretical evaluations, we conduct extensive experiments to evaluate our scheme’s computational and storage efficiency. These evaluations indicate that our solution outperforms previous solutions and as well as preserves many desired functionalities.

While real-time electricity consumption data of users in smart grids can enable value-added services, such as Big Data analytics, each individual user's privacy needs to be protected. How to balance data utility and privacy protection is a significant issue, of which privacy-preserving data aggregation (PPDA) is a viable solution. Prior to this, researchers have proposed a number of PPDA schemes to address the above challenge. Unluckily, most of them suffer from security and privacy drawbacks, while others are inappropriate for resource-limited smart meters due to high cost of cryptographic operations. To tackle this issue, in this article, we propose a pairing-free and exponentiation-free certificateless PPDA scheme named CL-PPDA for smart grids. We prove the security of our design and analyze its performance. Comparative analyses with state-of-the-art work in theory and experiment show that our design not only has better security properties, but also has competitive computation overhead, especially on the resource-constrained smart meter side. Besides, we present an extension of our CL-PPDA scheme to support multidimensional data aggregation, which further enriches the functionality of our design.

In this paper, we initiate the study of the Rank Decoding (RD) problem and Low Rank Parity Check (LRPC) codes with blockwise structure in rank-based cryptosystems. First, we introduce the blockwise errors ($\ell $-errors) where each error consists of$\ell $blocks of coordinates with direct-sum supports, and define the blockwise RD ($\ell $-RD) problem as a natural generalization of the RD problem whose solutions are$\ell $-errors (note that the RD problem is actually a special$\ell $-RD problem with$\ell =1$). We adapt the typical attacks on the RD problem to the$\ell $-RD problem, and find that the blockwise structure does not ease the problem too much: the$\ell $-RD problem is still exponentially hard for appropriate choices of$\ell \gt 1$. Second, we introduce the blockwise LRPC ($\ell $-LRPC) codes as generalizations of the LPRC codes whose parity-check matrices can be divided into$\ell $sub-matrices with direct-sum supports, i.e., the intersection of two subspaces generated by the entries of any two sub-matrices is a null space, and investigate the decoding algorithms for$\ell $-errors. We find that the gain of using$\ell $-errors in decoding capacity outweighs the complexity loss in solving the$\ell $-RD problem, which makes it possible to design more efficient rank-based cryptosystems with flexible choices of parameters. As an application, we show that the two rank-based cryptosystems submitted to the NIST PQC competition, namely, RQC and ROLLO, can be greatly improved by using the ideal variants of the$\ell $-RD problem and$\ell $-LRPC codes. Concretely, for 128-bit security, our RQC has total public key and ciphertext sizes of 2.5 KB, which is not only about 50% more compact than the original RQC, but also smaller than the NIST Round 4 code-based submissions HQC, BIKE, and Classic McEliece.

As a promising technology, key-aggregation searchable encryption with constant computation overhead is especially suitable for sensor nodes with limited computation resources in wireless sensor networks. However, in most of the existing key-aggregation searchable encryption schemes, the authorized aggregation key is generated in a deterministic way. As a result, these schemes suffer from “Key Forge Attack” and “Trapdoor Forge Attack” that we proposed and hence fail to support the security property as they claimed (which is an important goal to be achieved in key-aggregation searchable encryption schemes). To fix these flaws, in this paper, we identify the security challenges related to key-aggregation searchable encryption and propose a lightweight key-aggregation authorized searchable encryption scheme based on attribute-based encryption, called KA$^{2}$SE. It enables a data owner to share encrypted data with an authorized query user by issuing only a single authorized aggregation key, and the authorized query user only needs to submit a single trapdoor to the cloud server to perform keyword search. We formulate the security definitions for KA$^{2}$SE and prove its security. Finally, empirical evaluations demonstrate that KA$^{2}$SE is computationally efficient in comparison with existing schemes.

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 The MinRank problem is an NP-complete problem that is prevalent in multivariate cryptography and its goal is to find a non-zero linear combination of given a series of matrices over a ring such that the obtained matrix has a small rank. At Asiacrypt 2001, two Zero-Knowledge Proofs of Knowledge (ZKPoK) for the MinRank problem are proposed, and we call them MRZK and MRZK$^{\dagger }$, respectively. The latter is an improved version of the proof size of the former. However, the efficiency of MRZK$^{\dagger }$ has been open and not analyzed. While the MRZK protocol is secure, it must be repeated many times due to the soundness error $2/3$, which leads to the large proof size. For 128-bit security, the MRZK protocol is executed at least 219 iterations and the proof size is about 32 KB. In this paper, we first show that the efficiency of MRZK$^{\dagger }$ is impractical due to unreasonable parameter size. However, when the parameter size is tuned and the efficiency is improved, an imposter can be efficiently constructed. Then, to alleviate the large proof size of MRZK, inspired by the technique designing ZKPoK (Eurocrypt 2020), we propose a sigma protocol with helper to prove the solution to the MinRank problem. Finally, we transform the sigma protocol with helper into a standard ZKPoK (MRZK$^{\sharp }$) by removing the helper. The MRZK$^{\sharp }$ protocol can achieve any small soundness error and enjoy the proof size of about 15 KB (53% improvement over MRZK).

Reputation systems are widely used to provide a trustworthy environment and improve the sustainability of online discussions. They help users understand and evaluate the quality of information by collecting and counting feedback from different users. However, a common issue in most reputation systems is how to maintain users’ reputation and protect their anonymity simultaneously. In this paper, we introduce a new practical anonymous reputation system based on SGX. The establishment of an anonymous reputation system has a positive effect on sustainable trust in reputation-based online applications. Our system achieves the combination of reputation and anonymity by utilizing Intel SGX and the Bloom filter. The Path ORAM algorithm is also implemented to resist side-channel attacks. The experiments demonstrate that our system achieves high performance in terms of computation and storage costs. When compared to two state-of-the-art anonymous reputation systems, our system has better computation performance with at least three orders of magnitude.

Abstract Redactable signatures allow the signature holder to remove admissible data blocks in the signed data while generating valid signatures about different redacted data without communicating with the primary signer. Now, this sort of signature has attracted widespread attention due to its many application scenarios such as electronic medical records, smart grids and XML files. However, there are rarely redactable signature schemes that can resist quantum attacks so far. In the wake of quantum calculation era, it is essential to blossom more quantum-resistant redactable signatures for different data structures. Moreover, it is popular to use accumulators to design redactable signature schemes. Unfortunately, the existing accumulators do not support tree data structures. Therefore, this paper first gives the definition of accumulator schemes for trees, and designs a lattice-based accumulator scheme for trees. Our accumulator scheme features shorter accumulator values and a faster witness generation algorithm than existing lattice trapdoor accumulators. Second, this paper resorts to approximate trapdoors and the preimage sampleable technique, and presents a lattice-based redactable signature scheme for trees using our accumulator scheme. Meanwhile, this scheme fulfills unforgeability, transparency and privacy under adaptive chosen-message attacks. Furthermore, the experiment results show that the redactable signature scheme meets actual revision requirements well.

Incentive-based applications enable users to obtain rewards after they complete a task, but how to balance the privacy and accountability is one of the most serious concerns currently. Publicly accountable anonymous authentication provides an excellent way verifying a user’s identity in a privacy-preserving way while ensuring public accountability in case of dispute. Although different kinds of these schemes have been proposed, they all assume that there is a single centralized certificate authority issuing a certificate to users, and are not suitable for an actual scenario which always involves multiple authorities. Therefore, a new primitive called multi-authority linkable and traceable anonymous authentication is proposed to address this issue, enabling privacy protection while holding public accountability under a multi-authority setting. We formally define a security model for this new notion and simultaneously design a generic construction while giving the security proof. Additionally, we implement the proposed scheme to show its efficiency.

Recent advancements in the Internet of Things (IoT) and cloud computing technologies have accelerated the development of various practical applications, including healthcare systems. Adequately revealing the collected healthcare data in a cloud-assisted healthcare IoT system brings a huge potential for improving the safety, quality, and efficiency of healthcare services. However, often the data collected in a healthcare IoT system is vital and sensitive. The dissemination of such data is also vulnerable to malicious attacks such as tampering, eavesdropping, and forgery. Thus, disseminated data's integrity, authenticity, and privacy are elementary security demands to end-users and owners. Also, the resource-constrained nature of healthcare IoT devices invalidates the existing solutions. To address the above challenges, we propose a lightweight and secure redactable signature scheme with coarse-grained additional redaction control (CRS) for secure dissemination of healthcare data in a cloud-assisted healthcare IoT system. The security analysis indicates our CRS is secure against signature forgery, additional redaction attacks, and redacted version linkability. Compared to other existing solutions, our scheme can achieve some level of security but less computational complexity and communication overhead.

Mobile devices have become near-ubiquitous tools in our daily lives. Following this trend, mobile commence is developed rapidly which in turns stimulates interests in mobile payment. Some prominent examples include Google’s Wallet, WeChat Pay, and Apple Pay. Most of these technologies, however, are designed for users to be able to pay conveniently to the business. In other words, they are designed with the business to user model in mind. Besides, an active network connection with an external payment server is required either from payer or payee during transaction. Our work intends to supplement existing solutions, which allows payment to be made in an off-line and dual-anonymous manner. In doing so, a dual-anonymous off-line electronic cash scheme is proposed by utilizing BBS+ signature. The feature of our scheme is dual-anonymous payment, which means that both the payer and the payee in any transaction cannot be identified even all other users and the payment server collude. Through security proof and performance analysis, we also demonstrate that the security of the proposed scheme can be reduced to standard assumptions and it is suitable for applications in mobile commerce.

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.

A privacy-preserving data analytics system enables a cloud user to perform the distributed job in a secure manner such that the data privacy can be guaranteed during the cloud-outsourced computation. However, many SGX-based solutions are vulnerable to some side-channel attacks, including the access pattern leakage from both network and memory. Several data-oblivious algorithms with full obliviousness have been proposed in the literature, but they are impractical to be used in the cloud due to the expensive computational overhead. In this article, we propose a DPSpark system with the security defined in a notion of$(\epsilon,\delta)$-differentially private obliviousness ($(\epsilon,\delta)$-DPO), which relaxes full obliviousness to enable an efficiency improvement. Based on this definition, we present a perturbation-shuffle-analysis (PSA) computing architecture and design several typical differentially oblivious operators. In further, we optimize the system efficiency by reducing the number of oblivious shuffles and choosing an appropriate privacy budget. Finally, we benchmark the system in different parameters. The experimental results show that DPSpark significantly outperforms two state-of-the-art solutions, only with 10.1-85.4 percent additional overhead performing an SGX-based data analysis application.

Abstract Image authentication is the process of verifying image origin, integrity and authenticity. In many situations, image authentication should allow reasonable image editing, which does not introduce any wrong information against the original one. While it has been studied both extensively and intensively with considerable efforts, there is no satisfactory method supporting region extraction. This paper presents a solution to address the issue of privacy protection in authenticated images. Our scheme allows anyone to extract sub-image blocks from an original image (authenticated by the image producer) and generate a proof tag to prove the credibility of the extracted image blocks. The process of proof tag generation does not require any interaction with the image producer. In addition, the image producer is able to define must-be-preserved image blocks (e.g. producer logo) during the extraction. We define the security property for the authenticated sub-images and give a generic design with two core primitives: an ordinary digital signature scheme and a cryptographic accumulator. The security of our design can be reduced to the underlying cryptographic primitives and its practical performance is demonstrated by a bunch of evaluations. We believe the proposed design, together with other image authentication methods, will further facilitate image relevant services and applications.

Abstract In a digital society, the rapid development of computer science and the Internet has greatly facilitated image applications. However, one of the public network also brings risks to both image tampering and privacy exposure. Image authentication is the most important approaches to verify image integrity and authenticity. However, it has been challenging for image authentication to address both issues of tampering detection and privacy protection. One aspect, image authentication requires image contents not be changed to detect tampering. The other, privacy protection needs to remove sensitive information from images, and as a result, the contents should be changed. In this paper, we propose a practical image authentication scheme constructed from chameleon hashes combined with ordinary digital signatures to make tradeoff between tampering detection and privacy protection. Our scheme allows legitimate users to modify contents of authenticated images with a privacy-aware purpose (for example, cover some sensitive areas with mosaics) according to specific rules and verify the authenticity without interaction with the original authenticator. The security of our scheme is guaranteed by the security of the underlying cryptographic primitives. Experiment results show that our scheme is efficient and practical. We believe that our work will facilitate image applications where both authentication and privacy protection are desirable.

With the increasing development of cloud computing, a number of users choose to outsource their data to a remote database service provider and enjoy flexible data sharing with multiple parties. However, the integrity and confidentiality of outsourced data in a remote cloud server are the main threats users are concerned about. The tree structure is one of the most widely used data organization structures. It is crucial to guarantee the integrity and privacy not only for the content but also for the structure if sensitive information is organized in this structure. At present, despite some solutions have been put forward, none of these considers the additional redaction attack on tree-structured data from attackers while sharing data with others. In this article, we provide a construction of secure redactable signature scheme for tree-structured data which features a multi-party control on the redaction of vertexes in a tree while the authenticity and privacy are assured. Then, we prove that our scheme is unforgeable, private, and transparent. Furthermore, extensive theoretical and experimental analyses are conducted to assess the efficiency of our scheme. The results demonstrate our scheme achieves multi-party redaction control without sacrificing sensible resources especially when a tree has a larger number of vertexes and siblings per vertex.

Electronic healthcare (eHealth) systems have replaced traditional paper-based medical systems due to attractive features such as universal accessibility, high accuracy, and low cost. As a major constituent part of eHealth systems, mobile healthcare (mHealth) applies Mobile Internet Devices (MIDs) and Embedded Devices (EDs), such as tablets, smartphones, and other devices embedded in the bodies of individuals, to improve the quality of life and provide more convenient healthcare services for patients. Unfortunately, MIDs and EDs have only limited computational capacity, storage space, and power supply. By taking this into account, we present a new design to guarantee the integrity of eHealth records and the anonymity of the data owner in a more efficient and flexible way. The essence of our design is a general method which can convert any secure Attribute-Based Signature (ABS) scheme into a highly efficient and secure Online/Offline Attribute-Based Signature (OOABS) scheme. We prove the security and analyze the efficiency improvement of the new design. Additionally, we illustrate the proposed generic construction by applying it to a specific ABS scheme.

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.

Summary With the popularity of mobile smart devices and functional diversification, the infection ways of mobile smartphones worm also become diverse. In mobile networks, mobile devices are suffering from the threat of worms all the time. Once the worm outbreaks, it will bring huge losses to mobile phone users and mobile network operators. Researches on mobile worm propagation model allow us to control and detect potential worm threat, according to the characteristics of worm's outbreak. In the paper, we put forward a worm propagation model based on the mobile network environment. After analyzing the model, we then give the simulation for controlling factors affecting worm propagation. This model allows us to have a certain understanding for the spread on the size and speed of the mobile worm and provide effective methods to control the spread of the mobile worm. Copyright © 2015 John Wiley & Sons, Ltd.

Smartphone is broadly applicable to the human activity recognition HAR mobile devices. However, energy consumption becomes a big obstacle to such mobile devices of real-time monitoring. In order to solve this problem, this paper presents a method of activity recognition based on energy-efficient schemes. In terms of data acquisition and processing, energy-efficient schemes adopt the best sample rate and extract the most effective feature combinations in accordance with the different activities, so as not to increase energy consumption; while in terms of recognition algorithm, we adopt the improved structure of multi-class support vector machine, combine it with the probability of activity occurrence, so as to reduce the time complexity of recognition. This method can minimize energy consumption greatly under the premise of maintaining higher recognition accuracy. Moreover, this paper adopts mobile cloud security technology to reduce potential risk of the smartphone's data transmission and processing. We present our work with an experimental study, and our experiments show that the accuracy of activity recognition based on energy-efficient schemes we proposed is up to 90.6%. In addition, this method will save 51.0% energy than that when sample rate and extracted features are, respectively, fixed at 100Hz and combined features. 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.

Electric Vehicle (EV) infrastructure is relatively new in many countries. Due to the recency of an EV infrastructure, it is important to carry out a series of testing programs. Furthermore, authenticity for collection of data is necessary for testing programs in order to provide accurate results. At the same time, user privacy should not cease since tracing one's daily logistic movements or behaviour from the EV testing programs means breaching one's privacy. In this paper, we propose a novel solution PEVTS for enabling both data authenticity and user privacy concurrently. Our proposed system provides great flexibility to the authority to choose any arbitrary set of authenticated users for testing in every time period. At the same time, it provides anonymity for all participating users. Yet it can trace any vehicle within a time period for statistical purpose. We give a detailed description of our system. We also implement the prototype of our system to show its practicality.

SUMMARY This paper presents two routing games, a unicast and a multicast routing game, for wireless sensor networks. We analyze the actions of nodes inside/outside lowest cost path (LCP) and draw their payoff functions. Our simulation shows that this evolutionary game theory scheme has several advantages over a widely used collusion–resistant routing scheme. All nodes, either out of LCP or in LCP, will ultimately choose the strategy ‘transmit’. To improve the payoff, nodes in LCP should either minimize their actual forwarding cost or maximize their claimed cost as long as it remains in the LCP, whereas minimizing the actual claimed cost is not an optimal option for nodes out of LCP. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT A cognitive wireless mesh (CogMesh) network can provide network access for users (mesh clients) while holding the open spectrum‐sharing feature. It combines the advantages of both cognitive radio networks and wireless mesh networks: high utilization of the scarce radio spectrum, ease of deployment, maintenance, and low cost. However, the unstable radio environment incurs more handoffs in CogMesh than other wireless networks. Therefore, seamless handoff and a lightweight re‐authentication process are required to achieve a high quality of real‐time applications and low network load caused by re‐authentication. In this paper, we introduce a local joint fast handoff scheme based on proxy signature, which is suitable for CogMesh scenarios. After the mutual authentication between a mesh client and a mesh router, a session tunnel key is derived and shared between them to protect their sessions. Because the proxy signature is used, the IEEE 802.1x authentication architecture remains the same, and there is no need for the authentication server to be involved in the handoff procedure, the re‐authentication delay has been reduced, and the load of CogMesh and the authentication server are lower. Copyright © 2013 John Wiley & Sons, Ltd.

We present a study of security in certificateless signatures. We divide potential adversaries according to their attack power, and for the first time, three new kinds of adversaries are introduced into certificateless signatures. They are Normal Adversary, Strong Adversary and Super Adversary (ordered by their attack power). Combined with the known Type I Adversary and Type II Adversary in certificateless cryptography, we then define the security of certificateless signatures in different attack scenarios. Our new security models, together with others in the literature, provide a clear definition of the security in certificateless signatures. Two concrete schemes with different security levels are also proposed in this paper. The first scheme, which is proven secure (in the random oracle model) against Normal Type I and Super Type II adversaries, has the shortest signature length among all known certificateless signature schemes. The second scheme is secure (in the random oracle model) against Super Type I and Type II adversaries. Compared with another scheme that has a similar security level, our second scheme requires less operational cost but a little longer signature length. Two server-aided verification protocols are also proposed to reduce the verification cost on the verifier.

Certificate-based encryption (CBE) and certificateless encryption (CLE) are proposed to lessen the certificate management problem in a traditional public-key encryption setting. Although they are two different notions, CBE and CLE are closely related and possess several common features. The encryption in CBE and CLE does not require authenticity verification of the recipient public key. The decryption in both notions requires two secrets that are generated by the third party and the public key owner, respectively. Recently a generic conversion from CLE to CBE was given, but unfortunately its security proof is flawed. This paper provides an elaborate security model of CBE, based on which a provably secure generic construction of CBE from CLE is proposed. A concrete instantiation is also presented to demonstrate the application of our generic construction.

Optimistic fair exchange (OFE) allows two parties to exchange their digital items in a fair way. As one of the fundamental problems in secure electronic business and digital rights management, OFE has been studied intensively since its introduction. This paper introduces and defines a new property for OFE: Strong Resolution-Ambiguity. We show that many existing OFE protocols have the new property, but its formal investigation has been missing in those protocols. We prove that in the certified-key model, an OFE protocol is secure in the multi-user setting if it is secure in the single-user setting and has the property of strong resolution-ambiguity. Our result not only simplifies the security analysis of OFE protocols in the multi-user setting but also provides a new approach for the design of multi-user secure OFE protocols. Following this approach, a new OFE protocol with strong resolution-ambiguity is proposed. Our analysis shows that the protocol is setup-free, stand-alone and multi-user secure without random oracles.

Optimistic fair exchange (OFE) protocols are useful tools for two participants to fairly exchange items with the aid of a third party who is only involved if needed. A widely accepted requirement is that the third party's involvement in the exchange must be transparent, to protect privacy and avoid bad publicity. At the same time, a dishonest third party would compromise the fairness of the exchange and the third party thus must be responsible for its behaviors. This is achieved in OFE protocols with another property called accountability. It is unfortunate that the accountability has never been formally studied in OFE since its introduction ten years ago. In this paper, we fill these gaps by giving the first complete definition of accountability in OFE where one of the exchanged items is a digital signature and a generic (also the first) design of OFE where transparency and accountability coexist.