Secret Key Size Research Articles

A traceable and revocable broadcast encryption scheme for preventing malicious encryptors in Medical IoT

Medical data sharing is essential for the advancement of medical research, but the existence of malicious encryptors and malicious users poses a major challenge to the seamless sharing of information among healthcare providers. We proposed a traceable and revocable broadcast encryption scheme for preventing malicious encryptors in the Medical Internet of Things (MIoT). In 2023, Wang et al. first proposed the concept of malicious encryptor for broadcast encryption and trator tracing, and they constructed a scheme for preventing this attack. The malicious encryptor is reasonable in real broadcast encryption systems because the encryptor is not always the same as the digital content provider. When digital content providers for medical institutions want to share sensitive medical data, the employees may implement encryption. Then the employees may plant some trapdoors and sell to the black market, which can be used to construct pirated boxes. To resist malicious encryptor attacks, we rely on the uniform distribution of the output of the secure cryptographic hash function to generate the randomness needed for encryption. To prevent malicious users from selling their private keys to attackers, we set up public tracing and revocation mechanisms. Meanwhile, we enable digital content providers to share common encrypted data to different groups of authorized users protected by privacy, while also sharing individual data to designated consumers of those groups. Under the decision q-parallel BDHE assumption without random oracles, our construction is demonstrated to be adaptive IND-CPA secure. Since we have a compact communication bandwidth, a constant user secret key size, and only three bilinear operations are needed for decryption to recover the encrypted broadcast message, our scheme does not add much overhead and is therefore practical.

Post-quantum secure fully-dynamic logarithmic-size deniable group signature in code-based setting

<p style='text-indent:20px;'>Since its introduction by Chaum and Heyst, <i>group signature</i> has been one of the most active areas of cryptographic research with numerous applications to computer security and privacy. Group signature permits the members of a group to sign a document on behalf of the entire group keeping signer's identity secret and enabling disclosure of the signer's identity if required. In this work, we present the first code-based fully-dynamic group signature scheme which allows group members to join or leave the group at any point of time. We employ a code-based updatable <i>Merkle-tree accumulator</i> in our design to achieve logarithmic-size signature and utilize randomized <i>Niederreiter</i> encryption to trace the identity of the signer. More positively, we equipped our scheme with <i>deniability</i> characteristic whereby the tracing authority can furnish evidence showing that a given member is not the signer of a particular signature. Our scheme satisfies the security requirements of <i>anonymity</i>, <i>non-frameability</i>, <i>traceability</i> and <i>tracing-soundness</i> in the random oracle model under the hardness of generic decoding problem. We emphasize that our scheme provides full-dynamicity, features deniability in contrast to the existing code-based group signature schemes and works favourably in terms of signature size, group public key size and secret key size.</p>

Multi-Client Boolean File Retrieval With Adaptable Authorization Switching for Secure Cloud Search Services

Secure cloud search services provide a cost-effective way for resource-constrained clients to search encrypted files in the cloud, where data owners can customize search authorization. Despite providing fine-grained authorization, traditional attribute-based keyword search (ABKS) solutions generally support single keyword search. Towards expressive queries over encrypted data, multi-client searchable symmetric encryption (MC-SSE) was introduced. However, current search authorizations of existing MC-SSEs:(i) cannot support dynamic updating; (ii) are (semi-)black-box implementations of attribute-based encryption; (iii) incur significant cost during system initialization and file encryption. To address these limitations, we present AasBirch, an MC-SSE system with fast fine-grained authorization that supports adaptable authorization switching from one policy to any other one. AasBirch achieves constant-size storage and lightweight time cost for system initialization, file encryption and file searching. We conduct extensive experiments based on Enron dataset in real cloud environment. Compared to state-of-the-art MC-SSE with fine-grained authorization, AasBirch achieves 30∼200× smaller public parameter and secret key size, with the assumed least frequent keyword in a query ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> -term) as 21. Moreover, it runs 10∼20× faster for file encryption and >20× faster for file searching. In addition, AasBirch outperforms 80,000× (resp. 7,850×) faster with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i> -term = 1 (resp. = 21), as compared to classic dynamic ABKS system.

Lattice-based group signatures with forward security for anonymous authentication

Group signatures allow users to sign messages on behalf of a group without revealing authority is capable of identifying the user who generated it. However, the exposure of the user's signing key will severely damage the group signature scheme. In order to reduce the loss caused by signing key leakage, Song proposed the first forward-secure group signature. If a group signing key is revealed at the current time period, the previous signing key will not be affected. This means that the attacker cannot forge group signatures regarding messages signed in the past. To resist quantum attacks, many lattice-based forward-secure group signatures have been proposed. However, their key-update algorithm is expensive since they require some costly computations such as the Hermite normal form (HNF) operations and conversion from a full-rank set of lattice vectors into a basis.In this paper, we propose the group signature with forward security from lattice. In comparison with previous works, we have several advantages: Firstly, our scheme is more effective since we only need to sample some vectors independently from a discrete Gaussian during the key-update algorithm. Secondly, the derived secret key size is linear instead of quadratic with the lattice dimensions, which is more friendly towards lightweight applications. Anonymous authentication plays an increasingly critical role in protecting privacy and security in the environment where private information could be collected for intelligent analysis. Our work contributes to the anonymous authentication in the post-quantum setting, which has wide potential applications in the IoT environment.

Rank AGS Identification Scheme and Signature Scheme

The identification protocol is a type of zero-knowledge proof. One party (the prover) needs to prove his identity to another party (the verifier) without revealing the secret key to the verifier. One can apply the Fiat–Shamir transformation to convert an identification scheme into a signature scheme which can be used for achieving security purposes and cryptographic purposes, especially for authentication. In this paper, we recall an identification protocol, namely the RankID scheme, and show that the scheme is incorrect and insecure. Then, we proposed a more natural approach to construct the rank version of the AGS identification protocol and show that our construction overcomes the security flaws in the RankID scheme. Our proposal achieves better results when comparing the public key size, secret key size, and signature size with the existing identification schemes, such as Rank RVDC and Rank CVE schemes. Our proposal also achieves 90%, 50%, and 96% reduction for the signature size, secret key size, and public key size when compared to the Rank CVE signature scheme.

Multiauthority Attribute-Based Access Control for Supply Chain Information Sharing in Blockchain

Information sharing has become an important application in modern supply chain management systems with business technology development. Because traditional supply chain information systems have problems such as easy data tampering, low information transparency, and interaction delays, blockchain has been taken consideration into supply chain information sharing research. Furthermore, blockchain technology is expected to provide decentralized supply chain information sharing solutions to enhance security, availability, and transparency. However, with the in-depth study of the application of blockchain technology in supply chain information sharing, people have found that the data stored publicly in the blockchain are still threatened by privacy leakage. In addition, due to the openness and accessibility of the blockchain, the lack of fine-grained access control is also apparent. In order to improve the security of data, we propose a novel privacy-preserving multiauthority attribute-based access control scheme for secure blockchain-based information sharing in a supply chain. In this scheme, blockchain stores encrypted supply chain information on distributed nodes. Multiple attribute authorities manage different attributes of users to achieve fine-grained access control and flexible authorization. Even if some attribute authorities fail, the user’s private key will not be leaked. In user secret key generation, we adopt an anonymous key generation protocol to realize the secure distribution of user keys by the attribute authorities. Furthermore, in order to meet the protection of communication privacy between blockchain nodes, properties of policy hiding and identity hiding are considered. Finally, we design experiments to analyze the performance of our scheme, including secret key sizes and running time of encryption and decryption.

MACFI: A multi-authority access control scheme with efficient ciphertext and secret key size for fog-enhanced IoT

With the rapid development of Internet of things (IoT), the number of connected devices and the data generated by them are increasing dramatically. This led to the development of paradigm fog computing, which facilitates data analysis and processing at the edge. Along with fog, cloud co-exists to provide massive storage, processing resources, etc. However, data storage and computation at multiple levels raise the risk of data security. Ciphertext-policy attribute-based encryption (CP-ABE) is a well-known cryptographic technique for providing fine-grained access control. Unfortunately, the existing multi-authority CP-ABE schemes are incompatible with resource-limited IoT devices as the ciphertext and secret key size grow linearly with the number of attributes. Therefore, we propose a multi-authority CP-ABE scheme named MACFI, where the ciphertext and secret key size are efficient. The size of the secret key held by the user is constant irrespective of the number of attributes. And, the ciphertext size increases linearly with the number of authorities rather than the number of attributes. Further, expensive decryption operations are outsourced to fog, which reduces the computation overhead of data users. Additionally, the overall encryption and decryption time are highly efficient. According to security and performance analysis, MACFI is secure and suitable for IoT applications.

Low-cost lightweight-client twin-field quantum key distribution network with wavelength division multiplexing

In recent years, quantum communication technology has gradually entered the practical stage. Multiple quantum key distribution (QKD) networks have been built and tested all over the world. However, quantum communication networking mode always evolves from a point-to-point network to a many-to-many network. The major challenges in quantum communication are secret key rate, distance, cost, and size of QKD devices. We proposed a low-cost, lightweight-client, twin-field QKD network with wavelength division multiplexing (WDM). The proposed implementation adopts polarization multiplexing, time-division multiplexing, and WDM technology to solve all these major challenges and implement a many-to-many dynamic communications network. Furthermore, our scheme can effectively reduce the cost to less than half of that of current QKD networks and has reference significance for large-scale deployment of QKD networks.

Алгебраические алгоритмы ЭЦП, основанные на трудности решения систем уравнений

Purpose of work is the development of post-quantum digital signature algorithms with comparatively small sizes of the public and secret keys and the signature. Research method is the use of a new concept for constructing signature algorithms on finite non-commutative associative algebras, which is distinguished by the multiple occurrences of the signature S in the power verification equation. A public key is generated in the form of a set of vectors every of which is calculated as the product of triples of secret vectors. With a special choice of these triples, it is possible to calculate a signature that satisfies the verification equation. Results of the study are two developed algebraic post-quantum digital signature algorithms of a new type, security of which is based on the computational difficulty of solving systems of many quadratic equations with many unknowns. The difference from the public-key algorithms of multivariate cryptography is that the system of quadratic equations is derived from the formulas for generating the public-key elements in the form of a set of vectors of m-dimensional finite non-commutative algebra with an associative vector multiplication operation. The said formulas define the system of n quadratic vector equations, which reduces to the system of mn quadratic equations over a finite field. Thanks to the “natural” mechanism for the occurrence of the specified system, it is set above the field, the order of which has a large size (97 and 129 bits). The used procedures for generating the public key and signature include the exponentiation operations to the degree of a large size (96 and 128 bits), which are performed over the elements of the secret (hidden) commutative group contained in the algebra. The signature is formed in the form of two elements: a randomizing natural number e and a “fitting” vector S. The signature authentication equation includes a multiple occurrence of the S element and every entry of the vector S is associated with the formation of a product that is exponentiated to a degree dependent on the value of the e element. A significant reduction in the size of public and secret keys and signatures has been achieved, as well as an increase in performance compared to foreign analogues, considered currently as basic algorithms for the adoption of post-quantum digital signature standards.

Efficient identity-based encryption with Hierarchical key-insulation from HIBE

Hierarchical key-insulated identity-based encryption (HKIBE) is identity-based encryption (IBE) that allows users to update their secret keys to achieve (hierarchical) key-exposure resilience, which is an important notion in practice. However, existing HKIBE constructions have limitations in efficiency: sizes of ciphertexts and secret keys depend on the hierarchical depth. In this paper, we first triumph over the barrier by proposing simple but effective design methodologies to construct efficient HKIBE schemes. First, we show a generic construction from any hierarchical IBE (HIBE) scheme that satisfies a special requirement, called MSK evaluatability introduced by Emura et al. (Des. Codes Cryptography 89(7):1535–1574, 2021). It provides several new and efficient instantiations since most pairing-based HIBE schemes satisfy the requirement. It is worth noting that it preserves all parameters’ sizes of the underlying HIBE scheme, and hence we obtain several efficient HKIBE schemes under the k-linear assumption in the standard model. Since MSK evaluatability is dedicated to pairing-based HIBE schemes, the first construction restricts pairing-based instantiations. To realize efficient instantiation from various assumptions, we next propose a generic construction of an HKIBE scheme from any plain HIBE scheme. It is based on Hanaoka et al.’s HKIBE scheme (Asiacrypt 2005), and does not need any special properties. Therefore, we obtain new efficient instantiations from various assumptions other than pairing-oriented ones. Though the sizes of secret keys and ciphertexts are larger than those of the first construction, it is more efficient than Hanaoka et al.’s scheme in the sense of the sizes of master public/secret keys.

ETPAC: ECC based trauma plight access control for healthcare Internet of Things

Healthcare Industry experiences a rapid change in the traditional way of providing Medical Services to Patients with the revolution of the Internet of Things (IoT) and the Digitization of services. The Healthcare IoT (HIoT) provides Hospitals to render excellent services to Patients at an optimized cost. The Healthcare IoT must ensure not to disrupt or tamper with sensitive Medical Information of the Patient in addition to the continuous availability of data and services. The proposed framework is designed for secure emergency access to Patient data over Healthcare IoT. Normally, the Doctor obtains the Shared Key directly from the Patient to access the Medical data. In Trauma Plight, a Patient pre-shares an Attribute based Key with a set of Secondary Authority in Trauma Plight (SATP) and access permission to the Doctor for utilizing Emergency Key from SATP. The Doctor retrieves the medical record by using the Attribute based key and the Emergency-key to medicate the Patient in Trauma. The proposed ECC model based Trauma Plight Access Control (ETPAC) reduces the Shared Secret Key generation time, Encryption, Decryption Time, Cipher-Text size with low Secret Key Size. The performance analysis indicates the enhanced security with reduced time complexity of Computation and Communication in ETPAC compared to Lightweight Break-glass Access Control, an Efficient Policy Hiding Attribute Based Access Control, and an Efficient and Robust Attribute based Encryption Supporting Access Policy Hiding in Healthcare IoT.

State-of-the-Art Survey of Quantum Cryptography

In today Internet era, confidential information transmitted over an insecure channel. With the significant development in the area of quantum computing, there is a need for unconditional security in confidential information. Quantum key distribution protocols are proven secure if all devices are perfect (in terms of technologies and proper protocol operations). The major challenges in quantum communication are secret key rate, distance, cost and size of QKD devices. The purpose of this survey article is to carry out a systematic review in the area of quantum cryptography by covering various aspects of non-deterministic quantum key distribution protocols, quantum secure direct communication, semi-quantum key distribution, secure multiparty communication protocol, post-quantum cryptography and device-independent cryptography techniques. In addition, we also discussed various experimental work carried out in the area of quantum cryptography, various attacks and challenges relative to the paradigm shift from classical cryptography to quantum cryptography. Quantum cryptography will become a future replacement of classical cryptography techniques after the development of the first physical quantum computer.

A Compact Digital Signature Scheme Based on the Module-LWR Problem

We propose a new lattice-based digital signature scheme \(\textsf {MLWRSign} \) by modifying \(\textsf {Dilithium} \), which is one of the second-round candidates of NIST’s call for post-quantum cryptographic standards. To the best of our knowledge, our scheme MLWRSign is the first signature scheme whose security is based on the (module) learning with rounding (LWR) problem. Due to the simplicity of the LWR, the secret key size is reduced by approximately 30% in our scheme compared to Dilithium, while achieving the same level of security. Moreover, we implemented MLWRSign and observed that the running time of our scheme is comparable to that of Dilithium.

Forward-Secure Multi-User Aggregate Signatures Based on zk-SNARKs

As a solution to mitigate the key exposure problems in the digital signature, the forward security has been proposed. The forward security guarantees the integrity of the messages generated in the past despite leaks of a current time period secret key by evolving a secret key on each time period. In this paper, we propose a new forward secure aggregate signature scheme utilizing recursive zk-SNARKs (zero knowledge Succinct Non-interactive ARguments of Knowledge). Our proposal has constant complexities in key/signature sizes, signature generation, and verification time. The proposed forward secure signature scheme can aggregate signatures generated by multiple users as well as a single user. The security of the proposed scheme is formally proven under zero-knowledge assumption and random oracle model. The experiment results show that our signature scheme yields 12 s for signing time, 1 ms for verification time, 25 s for aggregation time, with the 1.6 KB secret key size and signature size independent of the number of time periods.

Fast Modular Multipliers for Supersingular Isogeny-Based Post-Quantum Cryptography

As one of the postquantum protocol candidates, the supersingular isogeny key encapsulation (SIKE) protocol delivers promising public and secret key sizes over other candidates. Nevertheless, the considerable computations form the bottleneck and limit its practical applications. The modular multiplication operations occupy a large proportion of the overall computations required by the SIKE protocol. The VLSI implementation of the high-speed modular multiplier remains a big challenge. In this article, we propose three improved modular multiplication algorithms based on an unconventional radix for this protocol, all of which cost about 20% fewer computations than the prior art. Besides, a multiprecision scheme is also introduced for the proposed algorithms to improve the scalability in hardware implementation, resulting in three new algorithms. We then present very efficient high-speed constant-time modular multiplier architectures for the six algorithms. It is shown that these new architectures can be extensively pipelined and highly optimized to obtain high throughput and low latency. The field-programmable gate array (FPGA) implementation results show that all proposed multipliers achieve much higher throughput than previous designs, but the increase in resources is relatively small. In addition, the multipliers without the multiprecision scheme have very low latency, which is very friendly to high-speed applications of the SIKE protocol.

An efficient identity-based proxy signcryption using lattice

Signcryption combines the functionalities of digital signature and encryption in a single step, which promises to increase the efficiency and the confidentiality of on-line transactions. Identity-based proxy signcryption integrates the functions of identity-based cryptography, proxy signature and signcryption. However, identity-based proxy signcryption constructed on the discrete logarithm and the integer factoring problems cannot defeat quantum attack. Therefore, the paper proposes a lattice-based identity-based proxy signcryption since there are none efficient quantum algorithms to attack lattice-based cryptography. The constructed scheme has the properties of both signcryption and proxy signature, i.e., the constructed scheme has ind-cca2 security, suf-cma security, strong identifiability, strong undeniability and key dependence properties. Comparing with the known identity-based proxy signcryption, the proposed scheme needs smaller computation complexity, smaller secret key size and smaller signature tuple size. Besides, the proposed scheme does not depend on the public key infrastructure since it is an identity-based cryptography.

Secrecy by Design With Applications to Privacy and Compression

Secrecy by design is examined as an approach to information-theoretic secrecy. The main idea behind this approach is to design an information processing system from the ground up to be perfectly secure with respect to an explicit secrecy constraint. The principal technical contributions are decomposition bounds that allow the representation of a random variable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> as a deterministic function of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$({S},{Z})$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> is a given fixed random variable and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z$ </tex-math></inline-formula> is constructed to be independent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> . Using the problems of privacy and lossless compression as examples, the utility cost of applying secrecy by design is investigated. Privacy is studied in the setting of the privacy funnel function previously introduced in the literature and new bounds for the regime of zero information leakage are derived. For the problem of lossless compression, it is shown that strong information-theoretic guarantees can be achieved using a reduced secret key size and a quantifiable penalty on the compression rate. The fundamental limits for both problems are characterized with matching lower and upper bounds when the secret <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> is a deterministic function of the information source <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> .

PKC‐PC: A variant of the McEliece public‐key cryptosystem based on polar codes

Polar codes are novel and efficient error-correcting codes with low encoding and decoding complexities. These codes have a channel-dependent generator matrix, which is determined by the code dimension, code length and transmission channel parameters. A variant of the McEliece public-key cryptosystem based on polar codes, called the PKC-PC, is studied. Since the structure of the polar codes’ generator matrix depends on the parameters of the channel, the authors have used an efficient approach to conceal their generator matrix. The proposed approach is based on a random selection of rows of the matrix by which a random generator matrix is constructed. Using the characteristics of polar codes and introducing an efficient approach, they could reduce the public and secret key sizes, and computational complexity compared to the McEliece cryptosystem. Moreover, they show that PKC-PC yields an increased security level against conventional attacks as well as possible vulnerabilities to the code-based public-key cryptosystems. Furthermore, they prove the security of the authors’ cryptosystem and show that its security is reduced to solve NP-complete problems, called polar parameterised syndrome decoding and polar parameterised codeword existence.

Anonymity in traceable cloud data broadcast system with simultaneous individual messaging

Internet of Things (IoT) and cloud computing are separate emerging paradigms, which are both an indispensable part of numerous ubiquitous devices that are connected to our life via the Internet. Their enactment and effectiveness are presumed to be more and more pervasive, making them essential ingredients of the Future Internet. Cloud data broadcast system is a novel framework where the advancement of both cloud and IoT is merged and becomes an enabler of a vast number of application scenarios. A data broadcast system with simultaneous individual messaging, aka broadcast encryption with personalized messages (BEPM), outsources not only a common encrypted message to a group of consumers but also encrypted personalized messages to individual consumers of the cloud server. Currently available BEPM are not secure against social engineering attacks, which means information of subscribed consumers is available to enemies. In this article, we present a new cloud data broadcast paradigm, called anonymous cloud data broadcast system with simultaneous individual messaging, in which anonymity of subscribed consumers is a primary concern. Furthermore, we extend our study of anonymization to develop the first traceable cloud data broadcast system with simultaneous individual messaging that concatenates two mutually orthogonal functionalities, namely consumer’s anonymity and traitor consumers traceability, in a unified manner. In particular, security and performance analysis explicates that both the designs are very cost-effective as consumer’s secret-key size is constant that fulfills the goals of achieving low overhead and computational cost for resource-constrained IoT devices.

ECC2: Error correcting code and elliptic curve based cryptosystem

Code-based cryptography has aroused wide public concern as one of the main candidates for post quantum cryptography to resist attacks against cryptosystems from quantum computation. However, the large key size becomes a drawback that prevents it from wide practical applications although it performs pretty well on the speed of both encryption and decryption. The use of algebraic geometry codes is considered to be a good solution to reduce the key size, but the special structures of algebraic geometry codes results in lots of attacks including Minder’s attack. To cope with the barriers of large key size as well as attacks from the special structures of algebraic codes, we propose a code-based encryption system using elliptic codes. The special structure of elliptic codes helps us to effectively reduce the size of secret key. By choosing the rational points carefully, we build elliptic codes whose minimum weight codeword is hard to sample. Such codes are used in constructing encryption systems such that Minder’s attacks can be resisted. More importantly, we apply the list decoding algorithm in the decryption process thus more errors beyond half of the minimum distance of the code could be corrected, which is the key point to resist other known attacks for algebraic geometry codes based cryptosystems. Our implementation shows that the proposed encryption system performs well on the key size and ciphertext expansion rate.