The digital transformation of healthcare necessitates advanced mechanisms for secure, privacy-preserving data sharing. Traditional methods struggle with the complexities of modern application scenarios such as cross-domain collaboration. We propose a privacy-preserving medical healthcare intelligent system built upon a novel Distributed Dynamic Threshold Attribute-based Encryption (DDTABE) scheme. Our DDTABE scheme is proven to achieve IND-CPA security under the aMSE-DDH hardness assumption in the random oracle model. The resulting system facilitates secure cross-domain medical data sharing and allows medical personnel to join dynamically for flexible collaboration. A key feature is its robustness as it resists unauthorized attributes through a verifiable mechanism. Performance analysis and experimental comparisons demonstrate the efficiency of our approach. Specifically, our scheme exhibits significant advantages in the running times of the Setup, Encrypt, and Decrypt algorithms compared to existing work, as the sizes of attribute sets in keys and policies grow, while maintaining constant ciphertext complexity.

Cloud-assisted Internet of Vehicles (IoV) enables real-time data collection and processing through vehicle–cloud collaboration, thereby improving traffic scheduling efficiency and safety. However, ensuring data privacy and verifying data authenticity remain major challenges in such systems. Although existing primitives such as matchmaking encryption (ME) provide partial protection, they still lack quantum resistance and forward security for historical data. To address this limitation, we propose a lattice-based puncturable identity-based match-making encryption (PIB-ME) scheme, and design a revocable data sharing system with bilateral access control (RDSS-BAC) tailored for cloud-assisted IoV. We formalize the definition and security model of PIB-ME and prove its security under the RLWE assumption. The proposed PIB-ME enables bilateral access control between communicating vehicles, supports key puncturing for flexible revocation, and achieves post-quantum security. Security analysis demonstrates that, in addition to privacy and authenticity, the scheme resists tampering, collusion, and quantum attacks. Finally, theoretical complexity analysis and experimental evaluation confirm the efficiency and practicality of our scheme in cloud-assisted IoV scenarios.

Cloud-assisted Internet of Things (IoT) is a new paradigm to compensate for the disadvantage of limited resources in IoT and extend the functional boundary of IoT. How to preserve the data privacy while identifying the data source in cloud-assisted IoT is a huge challenge and many cryptographic primitives such as matchmaking encryption (ME) are hence introduced to reach this goal. However, we observe that these tools fail to deal with some rigorous cases in which the data owner does not want anyone to disclose the entire data and even authorized users can only obtain a specified part. In this paper, to address such issue, we design a privacy-preserving data computing system with bilateral access control (PDCS-BAC) for cloud-assisted IoT based on a new primitive called identity-based matchmaking functional encryption (IB-MFE). We give the formal definition and security model of IB-MFE, then present two concrete IB-MFE schemes for inner-product function. Thus, PDCS-BAC manages to simultaneously provide flexible privacy computation with enhanced data privacy, bilateral access control, and data authenticity. Finally, we conduct comprehensive performance evaluations to demonstrate the practicability of our schemes for cloud-assisted IoT.

Proof of Retrievability (POR) is an important cryptographic primitive that has attracted considerable attention in the research community for its ability to enable users to audit the integrity of outsourced files on cloud servers without retrieving them. A POR scheme with public verifiability further enhances usability by allowing users to delegate the auditing task to a third party, making it highly desirable for a wide range of applications. However, most existing publicly verifiable POR schemes derive their security from the computational hardness of discrete logarithm or factoring, making them vulnerable to quantum attacks. Although it is possible to construct quantum-resistant POR schemes with public verifiability upon hash trees or general lattices, the resulting schemes often exhibit performance limitations when compared to existing constructions, thereby limiting their deployment in real-world applications. In this work, we address this gap by constructing a publicly verifiable POR scheme on structured lattices. We show that our scheme is provably secure in the random oracle model under the Ring-LWE and Ring-SIS assumptions. We provide an implementation of our scheme and the experimental results show that its performance is comparable to certain well-known constructions based on traditional assumptions.

Data sharing technology plays an important role in sharing information on mobile devices, ensuring that users can preserve their privacy while guaranteeing secure data transmission. Matchmaking encryption is a novel cryptographic primitive that provides bilateral access control to maintain user trust and data integrity. However, this primitive faces a challenge in terms of achieving secure multi-receiver construction. In a multi-user environment, users need to encrypt the data many times, resulting in inefficiencies under this approach. To address this challenge, we focus on the underlying construction of identity-based broadcast matchmaking encryption (IBBME). This paper presents a new IBBME construction with DBDH andq-SDH assumptions under the standard model. Specifically, we propose a new approach that abandons the generalized transformations that already existed previously in multiple receivers. Specifically, we adopt the “two-level” method to guarantee privacy and authenticity, where the identity-based broadcast encryption (IBBE) level guarantees privacy, while the signature level guarantees authenticity. In addition, we present a strict security proof, which shows that our construction satisfies privacy and authenticity exactly. Moreover, we compare the existing ME constructions with our construction through theoretical and performance analysis. The analysis shows that the ciphertext size in our construction can be reduced to be independent of the number of receivers, which is more efficient.

Abstract Dynamic searchable symmetric encryption (DSSE) with forward and backward privacy makes it possible to perform search on the outsourced encrypted database efficiently while still allowing updates under acceptable leakage. Current forward and backward private DSSE (FB-DSSE) scheme proposed by Zuo et al. cannot support conjunctive keyword query and the cloud server needs to be honest-but-curious. Recent FB-DSSE scheme supporting conjunctive keyword query proposed by Patranabis et al. cannot verify search results. On the other hand, searchable symmetric encryption scheme proposed by Wang et al. that supports conjunctive keyword query and the verification of search results cannot achieve forward and backward privacy. The problem of constructing a verifiable conjunctive FB-DSSE scheme is still open. In this paper, we propose a verifiable conjunctive dynamic searchable symmetric encryption scheme (VCDSSE). VCDSSE is a FB-DSSE scheme that additionally supports the verification of search results and conjunctive keyword query. We revisit homomorphic MAC to enable efficient verification of search results, adopt the technique of oblivious cross-tags to achieve conjunctive keyword query and utilize state chain to ensure forward and backward privacy. The formal security analysis and performance evaluation demonstrate that VCDSSE is secure and practical as compared with Mitra scheme in terms of search time.

We present an inner‐product matchmaking encryption (IP‐ME) scheme achieving weak privacy and authenticity in prime‐order groups under symmetric external Diffie–Hellman (SXDH) assumption in the standard model. We further present an IP‐ME with Monotone Span Program Authenticity (IP‐ME with MSP Auth) scheme, where the chosen sender policy is upgraded to MSP, and the scheme also achieves weak privacy and authenticity in prime‐order groups under SXDH assumption in the standard model. Both of the schemes have more expressive functionalities than identity‐based matchmaking encryption (IB‐ME) scheme, and are simpler than Ateniese et al.’s modular ME scheme (Crypto’ 19). But our schemes only achieve a very limited flavor of security, which is reflected in the privacy.

Abstract Identity‐based Matchmaking Encryption (IB‐ME) is an extension notion of matchmaking encryption (CRYPTO 2019), where a sender and a receiver can specify an access policy for the other party. In IB‐ME, data encryption is performed by not only a receiver identity but also a sender's encryption key. Nevertheless, previous IB‐ME schemes have not considered the problem of efficient revocation . Hence, the authors introduce a new notion of revocable IB‐ME (RIB‐ME) and formalise the syntax and security model of RIB‐ME. In particular, the authors give an effective and simple construction of RIB‐ME in the standard model, whose security is reduced to the hardness of decisional bilinear Diffie—Hellman problem and computational Diffie—Hellman problem. In addition, the authors show two extensions of our RIB‐ME scheme to consider chosen‐ciphertext security and forward privacy.

As cloud computing is widely used in a variety of different applications, how to continuously improve the efficiency of processing data while protecting data privacy and security is still a problem worth investigating. Existing searchable encryption schemes mainly focus on the exact matching patterns, which are insufficient to meet and cope with the increasing demands for fuzzy search. In particular, there has been a lack of attention to the research on practical and privacy-preserving fully wildcard searchable encryption. In this article, we propose a new wildcard searchable encryption system, which is built based on a novel inner product encryption scheme that can address the above challenges simultaneously. A two-dimensional inner product relation is introduced to remove all restrictions on wildcards, allowing our system to support fully wildcard search. To resist active attacks from malicious adversaries and prevent information leakage, we enhance the security to adaptive simulation-based security under the SXDH assumption. The corresponding security proof of our construction is implicitly established on a hash proof system. Our elaborately constructed system removes redundant parameters and extra complex computations, ensuring its practicality and efficiency. Finally, our system shows better performance in more than 86% of cases in the conducted experiments.

Abstract Binary tree encryption is an intriguing primitive that enables many practical applications to achieve an increasing important security feature, forward security. However, the public key size of existing constructions grows linearly with the depth of the underlying binary tree in the standard model. To support more secret keys associated with nodes, it is often expected that the tree has a sufficiently large depth. This places a burden on employing it implicitly or explicitly in real world. In this work, we show how to compress linear-size public key down to constant-size public key and give our construction featuring constant-size public key in the standard model. We prove that our construction achieves an improved security, adaptive security, under the matrix decision Diffie–Hellman assumption, which is a generalization of standard $k$-Lin assumption. Moreover, our key-generation, key-derivation and encryption algorithms have lower time complexity than that of the prior construction, leading to further efficiency improvements. To illustrate these improvements in practice, we give an implementation of our construction and the prior one and then evaluate the performance in the tree depth.

Cloud storage has become a primary industry in remote data management service but also attracts security concerns, where the best available approach for preventing data disclosure is encryption. Among them the public key encryption with keyword search (PKSE) is considered to be a promising technique, since clients can efficiently search over encrypted data files. That is, a client first generates a search token when to query data files, the cloud server uses the search token to proceed the query over encrypted data files. However, a serious attack is raised when PKSE meets cloud. Formally speaking, the cloud server can learn the information of a newly added encrypted data file containing the keyword that previously queried by using the search tokens it has received, and can further discover the privacy information. To address this issue, we propose a forward secure public key searchable encryption scheme, in which a cloud server cannot learn any information about a newly added encrypted data file containing the keyword that previously queried. To better understand the design principle, we introduce a framework for constructing forward secure public key searchable encryption schemes based on attribute-based searchable encryption. Finally, the experiments show our scheme is efficient.

Group signature with verifier-local revocation (VLR-GS) is a special variant of revocable group signature that not only allows a user to anonymously sign messages but also only requires the verifiers to possess some up-to-date revocation information. To date, a number of VLR-GS schemes have been proposed under bilinear groups and lattices, while they have not yet been instantiated based on coding theory. In this paper, we present a code-based VLR-GS scheme in the random oracle model, which is the first construction to the best of our knowledge. Concretely, our VLR-GS scheme does not rely on the traditional paradigm which utilizes an encryption scheme as a building block and achieves logarithmic-size group signature. To obtain the scheme, we first introduce a new code-based Stern-like interactive zero-knowledge protocol with member revocation mechanism based on syndrome decoding problem. Moreover, we employ the binary Goppa code embedded for our scheme with efficiency and security analysis.

Cloud computing is a new promising technology paradigm that can provide clients from the whole network with scalable storage resources and on-demand high-quality services. However, security concerns are raised when sensitive data are outsourced. Searchable encryption is a kind of cryptographic primitive that enables clients to selectively retrieve encrypted data, the existing schemes that support for sub-linear boolean queries are only considered in symmetric key setting, which makes a limitation for being widely deployed in many cloud applications. In order to address this issue, we propose a novel searchable asymmetric encryption scheme to support for sub-linear boolean query over encrypted data in a multi-client model that is extracted from an important observation that the outsourced database in cloud is continuously contributed and searched by multiple clients. For the purpose of introducing the scheme, we combine both the ideas of symmetric searchable encryption and public key searchable encryption and then design a novel secure inverted index. Furthermore, a detailed security analysis for our scheme is given under the simulation-based security definition. Finally, we conduct experiments for our construction on a real dataset (Enron) along with a performance analysis to show its practicality.

Cloud storage is a significant service provided by the cloud that enables users to store their immense data into the cloud. As the advent of the big data era, cloud storage services are becoming increasingly popular. For security reasons, data owners would like to check the integrity of their data after storing it in the cloud. To do this, they usually make use of the public cloud data integrity checking schemes. This paper focuses on user anonymity in such schemes so that no third party could infer the identity information of any data owner from checking procedures. The problem is obviously inevitable in reality, however the current solutions are relatively involved as they heavily use public key certificates and/or incur huge communication overhead. In this paper we introduce the concept of attribute-based cloud data integrity checking to achieve user anonymity lightly and present security models for such systems. We also provide a practical construction and prove its security in the random oracle model. Finally, we show how to extend our construction to protect data privacy against any third party.

Decentralized attribute-based encryption (ABE) is a special form of multiauthority ABE systems, in which no central authority and global coordination are required other than creating the common reference parameters. In this paper, we propose a new decentralized ABE in prime-order groups by using extended dual system groups. We formulate some assumptions used to prove the security of our scheme. Our proposed scheme is fully secure under the standard k -Lin assumption in random oracle model and can support any monotone access structures. Compared with existing fully secure decentralized ABE systems, our construction has shorter ciphertexts and secret keys. Moreover, fast decryption is achieved in our system, in which ciphertexts can be decrypted with a constant number of pairings.

In cloud computing, computationally weak users are always willing to outsource costly computations to a cloud, and at the same time they need to check the correctness of the result provided by the cloud. Such activities motivate the occurrence of verifiable computation (VC). Recently, Parno, Raykova and Vaikuntanathan showed any VC protocol can be constructed from an attribute-based encryption (ABE) scheme for a same class of functions. In this paper, we propose two practical and efficient semi-adaptively secure key-policy attribute-based encryption (KP-ABE) schemes with constant-size ciphertexts. The semi-adaptive security requires that the adversary designates the challenge attribute set after it receives public parameters but before it issues any secret key query, which is stronger than selective security guarantee. Our first construction deals with small universe while the second one supports large universe. Both constructions employ the technique underlying the prime-order instantiation of nested dual system groups, which are based on the $d$-linear assumption including SXDH and DLIN assumptions. In order to evaluate the performance, we implement our ABE schemes using $\textsf{Python}$ language in Charm. Compared with previous KP-ABE schemes with constant-size ciphertexts, our constructions achieve shorter ciphertext and secret key sizes, and require low computation costs, especially under the SXDH assumption.

The paper presents an identity based encryption (IBE) under selective opening attacks (SOA) whose security is almost-tightly related to a set of computational assumptions in composite-order bilinear groups. Our result is a combination of Bellare, Waters and Yilek's method [TCC, 2011] for constructing (not tightly) SOA secure IBE and Hofheinz, Koch and Striecks’ technique [PKC, 2015] on building almost-tightly secure IBE in the multi-ciphertext setting. In the paper, we first tune Bellare et al.’s generic construction for SOA secure IBE to show that a one-bit IBE achieving ciphertext indistinguishability under chosen plaintext attack in the multi-ciphertext setting (with one-sided public openability) tightly implies a multi-bit IBE secure under the selective opening attack. Next, we almost tightly reduce such a one-bit IBE to static assumptions in the composite-order bilinear groups employing the technique of Hofheinz et al. This yields the first SOA secure IBE with almost-tight reduction.

Rainbow is an effective multivariate digital signature scheme proposed by Ding and Schmidt. However, a lot of attacks against it have been proposed. To resist all these attacks, designer should be very careful with its choice of parameters. In this study, the authors will propose a new approach to build a secure variant of Rainbow. According to our security analysis, it could resist all the existing attacks against Rainbow and save some memory in the meantime.

Abstract Dual receiver encryption (DRE), a notion of public key encryption (PKE) introduced at CCS'04, allows two independent receivers to decrypt a ciphertext into a same plaintext. This crypto primitive is quite useful in designing denial of service attack‐resilient protocols. To our knowledge, prior DRE constructions are considered in the traditional PKE settings, which may face the difficulty of certificate management. This paper aiming at solving this dilemma of DRE in the traditional PKE settings, and gives an identity‐based variant version of DRE: identity‐based dual receiver encryption (ID‐DRE) that combines the notion of DRE and identity‐based encryption (IBE). Based on Waters' IBE (Crypto'05), two ID‐DRE schemes are constructed in the standard model and by partitioning methodology, provable security of our ID‐DRE schemes are obtained under the decisional bilinear Diffie‐Hellman. Furthermore, we achieve a tighter reduction by adopting a random walk ‐like methodology of analysis on the lower bound of simulators' artificial abort, which also results in better security tightness for Waters IBE. This improved result for Waters' IBE, where n is the bitlength of messages and q is the number of adversarial key queries, is consistent with Hofheinz and Kiltz's result (Crypto'08). Copyright © 2017 John Wiley & Sons, Ltd.