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The HQC post-quantum cryptosystem enables two parties to share noisy versions of a common secret binary string, and an error-correcting code is required to deal with the mismatch between both versions. This code is required to deal with binary symmetric channels with as large a transition parameter as possible, while guaranteeing, for cryptographic reasons, a decoding error probability of provably not more than 2-128. This requirement is non-standard for digital communications, and modern coding techniques are not amenable to this setting. This paper explains how this issue is addressed in the last version of HQC: precisely, we introduce a coding scheme that consists of concatenating a Reed–Solomon code with the tensor product of a Reed–Muller code and a repetition code. We analyze its behavior in detail and show that it significantly improves upon the previous proposition for HQC, which consisted of tensoring a BCH and a repetition code. As additional results, we also provide a better approximation of the weight distribution for HQC error vectors, and we remark that the size of the exchanged secret in HQC can be reduced to match the protocol security which also significantly improves performance. [ABSTRACT FROM AUTHOR]

A common strategy for constructing multivariate encryption schemes is to use a central map that is easy to invert over an extension field, along with a small number of modifications to thwart potential attacks. In this work, we study the effectiveness of these modifications, by deriving estimates for the number of degree fall polynomials. After developing the necessary tools, we focus on encryption schemes using the C ∗ and Dobbertin central maps, with the internal perturbation (ip), and Q + modifications. For these constructions, we are able to accurately predict the number of degree fall polynomials produced in a Gröbner basis attack, up to and including degree 5 for the Dob encryption scheme and four for C ∗ . The predictions remain accurate even when fixing variables. Based on this new theory, we design a novel attack on Dob, which completely recovers the secret key for the parameters suggested by its designers. Due to the generality of the presented techniques, we also believe that they are of interest to the analysis of other big-field schemes. [ABSTRACT FROM AUTHOR]

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It is becoming increasingly common to outsource data to the cloud. We recommend that the data owner encrypt his or her data ahead of outsourcing it to the cloud to ensure the confidentiality of the data. However, effective search for encrypted information is an essential and complex issue for cloud data sharing. In the past, searchable encryption (SE) has been proposed in many studies as the most promising solution for the efficient retrieval of encrypted data. However, these mechanisms are open to internal attacks that can be restored by assuming keywords from an open trapdoor (TPD) in an autonomous manner. This raises new security concerns, especially data confidentiality and security of cloud-based shared applications. In this paper, we present an efficient mechanism for the public key encryption method with authentication search (PKE-AS) which securely encrypts data using public-key cryptography and validates recipient authentication before retrieval with a shared secret key (SSK) exchange. The shared key is used by the sender to encrypt the keyword and by the receiver to generate a search TPD. The key idea of the proposal is to make sure that the system is safeguard the user data from intrusive keyword guessing attacks. This contribution provides a secure communication model for secure data sharing, searching and accessing by employing the key exchange protocol among the users. The comparison of PKE-AS with existing methods shows low executing time in analysis with different keyword search with encryption, TPD and Verification. It shows an average of 0.52ms less execution time in comparison results. The analysis of the experiment results demonstrates that the proposed method is suitable for practical use in cloud data sharing. [ABSTRACT FROM AUTHOR]

This paper deals with hardware implementations for lattice-based cryptography. Various CPA and CCA secure algorithms for LWE, RLWE and MLWE problems have been studied, parallelized, implemented and compared on FPGA using high-level synthesis. The impact of PRNG choices on the implementations performances and costs is also evaluated. HLS allows us to compare various sets of algorithms, architectures and parameters with a reduced design effort. Our results are often similar to state-of-the-art for various speed and cost trade-offs. Sometimes we obtain better results thanks to the exploration of numerous architecture and algorithm optimizations. [ABSTRACT FROM AUTHOR]

Conventional Public-Key Encryption (PKE) techniques are susceptible to possible attacks by quantum computers. Lattice-based cryptography presents promising solutions with quantum-safe hard problems like learning with rounding, short integer solutions, learning with errors, and Module Learning with Rounding (MLWR). Proposed work presents an efficient MLWR-based PKE scheme that utilizes number-theoretic transforms to significantly reduce polynomial multiplication time up to 40%. Additionally, scheme uses rounding operations to reduce public key size. Proposed scheme offers a balance between security and efficiency. Key generation, encryption, and decryption operations requiring 1422, 1040, and 2647 CPU cycles respectively and execution times for these operations are approximately 68.965, 34.483, and 34. 483 μ s. The scheme's security against chosen plaintext attacks is proven under the MLWR assumption. Security assessments using Martin Albrecht's estimator demonstrate that proposed parameter sets offer a high level of security (NIST's security categories) against Block Korkine–Zolotarev (BKZ) attacks. A comprehensive evaluation of the proposed PKE scheme has been conducted, focusing on its performance and security. The analysis includes a comparison with other lattice-based PKEs to highlight scheme's unique features and advantages. Performance of proposed PKE is comparable to existing efficient lattice-based alternatives, making it a compelling candidate for secure communication in the post-quantum era. [ABSTRACT FROM AUTHOR]

This paper presents a review of module ring learning with errors-based (MLWE-based) public-key encryption and key-establishment algorithms. In particular, we introduce the preliminaries of public key cryptography, MLWE-based algorithms, and arithmetic operations in post-quantum cryptography. We then focus on analyzing the state-of-the-art hardware architecture designs of CRYSTALS-Kyber at different security levels, including hardware architectures for Kyber-512, Kyber-768, and Kyber-1024. This analysis is dedicated to providing complete guidelines for selecting the most suitable CRYSTALS-Kyber hardware architecture to apply in post-quantum cryptography-based security systems in reality, with different requirements of security levels and hardware efficiency. [ABSTRACT FROM AUTHOR]

Cloud computing is a high demanding technology since the users and their data are increasing extremely day-by-day. Through an extensive utilization of cloud computing and storage devices, sensitive data is increasingly centralized into the cloud for reducing the maintenance cost which increases concerns about data privacy. One of the promising techniques to maintain the confidentiality of outsourced sensitive data is encryption schemes, however effective data utilization and also an efficient searching on encrypted data in cloud security are still challenging processes. Over the decades, many encryption techniques, namely Public-Key Encryption (PKE) and Identity-Based Encryption (IBE) with keyword searching and Equality Testing (ET) have been adopted to tackle those challenges over the encrypted data, but Private Matching (PM) over encrypted data is still difficult. In this paper, different researches based on PKEET and IBEET schemes in cloud computing are briefly studied which are utilized for data authorization and privacy-preserving. In addition, a comparative analysis is conducted to address the limitations in those schemes and suggest a further solution to tackle the identified issues. This survey helps us to overcome the PM over encrypted data in IBEET schemes and simplify the certificate management. [ABSTRACT FROM AUTHOR]

Recently, Horlemann-Trautmann and Weger (Adv Math Commun, https://doi.org/10.3934/amc.2020089, 2020) proposed a general framework for a Quaternary McEliece cryptosystem over the ring Z 4 , and generalized the construction over the ring Z p m where p is a prime integer. By considering the Lee metric, the public key size for the McEliece cryptosystems can be substantially smaller than their counterparts in the Hamming metric. Furthermore, the hardness of the McEliece cryptosystems over Z p m is based on the Lee Syndrome Decoding problem, which was shown to be NP-complete. This paper aims to analyze the design and security of the Lee metric McEliece cryptosystem over Z p m in the Lee metric. We derive some necessary conditions for the quaternary codes used in the Lee metric McEliece cryptosystem, and show that the theoretical quaternary codes proposed in (Adv Math Commun, https://doi.org/10.3934/amc.2020089, 2020) do not exist. Furthermore, we propose a plaintext recovery attack on the Lee metric McEliece cryptosystem over Z p m , when the minimum Lee distance of the underlying codes with certain structures is greater than twice the Lee weight of the error. Our plaintext recovery attack is applicable to the cryptosystems over Z p m when m > 1 . We apply our plaintext recovery attack on the Quaternary McEliece cryptosystem, and manage to recover partial plaintext of length k 1 within O 2 min { k 1 , 0.0473 n } operations, where n is the length of ciphertext. Hence, the proposed theoretical parameters for the Quaternary McEliece over Z 4 in (Adv Math Commun, https://doi.org/10.3934/amc.2020089, 2020) do not achieve 128-bit security, as we can recover the partial plaintext within 0.591 s. This also implies that the use of quaternary codes in the McEliece cryptosystem may not reduce the public key size significantly. Furthermore, for some parameters of the Lee metric McEliece cryptosystems over Z 4 , our plaintext recovery attack can be more efficient than the Lee-Brickell's and Stern's Information Set Decoding Algorithm over Z 4 . [ABSTRACT FROM AUTHOR]

In the past, the security of most public-key encryption or key encapsulation schemes is shown in an ideal model, where private keys, secret keys and random values are assumed to be absolutely secure to adversaries. However, this ideal model is not practical due to side-channel attacks in the sense that adversaries could gain partial information of these secret values involved in decryption operations by perceiving energy consumption or execution timing. In such a case, these schemes under the ideal model could suffer from side-channel attacks. Recently, leakage-resilient cryptography resistant to side-channel attacks is an emerging research topic. Certificate-based encryption (CBE) or certificate-based key encapsulation (CB-KE) schemes are a class of important public-key encryption. However, little work addresses the design of leakage-resilient CBE (LR-CBE) or leakage-resilient CB-KE (LR-CB-KE) schemes. In this paper, we present the first LR-CB-KE scheme with overall unbounded leakage property which permits adversaries to continuously gain partial information of the system secret key of a trusted certificate authority (CA), the private keys and certificates of users, and random values. In the generic bilinear group model, formal security analysis is made to prove that the proposed LR-CB-KE scheme is secure against chosen ciphertext attacks.

Public-key encryption is often used to protect data security/privacy and secure communication in scenarios of cloud computing and edge computing. Related randomness attacks model (RRA) for public-key encryption was motivated by randomness failures. This paper proposes some methods of constructing secure public-key encryption scheme against related randomness attacks, i.e. RRA-CPA secure public-key encryption scheme with efficient decryption algorithm and short ciphertexts size obtained from one-way function with weak RKA-security and indistinguishability obfuscation, RRA-CPA secure public-key encryption scheme against arbitrarily function from any publicly deniable encryption and RRA-CCA secure public-key encryption scheme against arbitrarily function from standard IND-CCA public-key encryption scheme with a hardcore function for arbitrarily correlated inputs.

With explosive era of machine learning development, human data, such as biometric images, videos, and particularly facial information, have become an essential training resource. The popularity of video surveillance systems and growing use of facial images have increased the risk of leaking personal information. On the other hand, traditional cryptography systems are still expensive, time consuming, and low security, leading to be threatened by the foreseeable attacks of quantum computers. This paper proposes a novel approach to fully protect facial images extracted from videos based on a post-quantum cryptosystem named NewHope cryptography. Applying the proposed technique to arrange input data for encryption and decryption processes significantly reduces encryption and decryption times. The proposed facial security system was successfully accelerated using data-parallel computing model on the recently launched Nvidia GTX 2080Ti Graphics Processing Unit (GPU). Average face frame extracted from video ($190\times 190$ pixel) required only $2.2~ms$ and $2.7~ms$ total encryption and decryption times with security parameters $n=1024$ and $n=2048$ , respectively, which is approximately 9 times faster than previous approaches. Analysis results of security criteria proved that the proposed system offered comparable confidentiality to previous systems.

Hardware security tokens have now been used for several decades to store cryptographic keys. When deployed, the security of the corresponding schemes fundamentally relies on the tamper-resistance of the tokens – a very strong assumption in practice. Moreover, even secure tokens, which are expensive and cumbersome, can often be subverted. We introduce a new cryptographic primitive called Encryption schemes with Password-protected Assisted Decryption (EPAD schemes), in which a user's decryption key is shared between a user device (or token) on which no assumption is made, and an online server. The user shares a human-memorizable password with the server. To decrypt a ciphertext, the user launches, from a public computer, a distributed protocol with the device and the server, authenticating herself to the server with her password (unknown to the device); in such a way that her secret key is never reconstructed during the interaction. We propose a strong security model which guarantees that (1) for an efficient adversary to infer any information about a user's plaintexts, it must know her password and have corrupted her device (secrecy is guaranteed if only one of the two conditions is fulfilled), (2) the device and the server are unable to infer any information about the ciphertexts they help to decrypt (even though they could together reconstruct the secret key), and (3) the user is able to verify that the device and the server both performed the expected computations. These EPAD schemes are in the password-only model, meaning that the user is not required to remember a trusted public key, and her password remains safe even if she is led to interact with a wrong server and a malicious device. We then give a practical pairixng-based EPAD scheme. Our construction is provably secure under standard computational assumptions, using non-interactive proof systems which can be efficiently instantiated in the standard security model, i.e., without relying on the random oracle heuristic. [ABSTRACT FROM AUTHOR]

Recently, Kim et al. proposed a modified Dual-Ouroboros public-key encryption (PKE ) using Gabidulin codes to overcome the limitation of having decryption failure in the original Dual-Ouroboros using low rank parity check codes. This modified Dual-Ouroboros PKE using Gabidulin codes is proved to be IND–CPA secure, with very compact public key size of 738 bytes achieving 128-bit security level. However, they did not specify on their choice of the secret key S used in their PKE . In this paper, we analyze different possible choices for S in the modified Dual-Ouroboros PKE using Gabidulin codes. More specifically, we show that if S is invertible over F q m without any restriction, then the decryption algorithm will fail. Furthermore, we show that Kim et al.'s proposal of the modified Dual-Ouroboros PKE using Gabidulin codes has secret key S over F q for its decryption algorithm to be correct. Then, we proposed two attacks: key recovery attack and plaintext recovery attack on their PKE with S over F q . We are able to recover the secret key for all the proposed parameters within 235 seconds. Moreover, we show that the public key matrix in their proposal generates a subcode of Gabidulin code. As a consequence, we can apply the Frobenius weak attack on their proposal and recover the plaintext for all the proposed paramters within 0.614 second. Finally, we give a proposal for the modified Dual-Ouroboros PKE using Gabidulin codes such that it is correct and secure, by considering certain restrictions on S over F q m . [ABSTRACT FROM AUTHOR]

Public-key encryption with equality (PKEET) test enables testing if two ciphertexts, possibly under two different public keys, encrypt the same messages. Recent research on PKEET considers the setting where the testing ability is delegated to semi-trusted parties to negate unfettered chosen-plaintext attacks. In this work, we revise and enhance the PKEET security model, and introduce a new property of unmaskability which further prevents an attacker from skirting the test. We then propose a simple and efficient PKEET system with adaptive chosen-ciphertext security, provably secure under our revised security model, from either plain or ring lattice assumptions. The construction adopts a direct approach which significantly departs from the existing way of building such systems. Compared with existing literature, our system relies on weaker learning-with-errors assumptions while also being more efficient and providing better security. [ABSTRACT FROM AUTHOR]