In this paper, we introduce a new hard problem opening up the construction for new quantum resistant cryptographic schemes. The latter is called Learning Rank with Errors (LRE) and can be seen as an adaptation of the LPN problem to the rank metric setting. In addition, we describe HBLRE, an HB-like authentication protocol that constitutes an application of the aforementioned problem. We also prove that HTLRE is secure against passive attacks and compare its parameters to those of the initial HB scheme.
In this paper, we introduce a new hard problem opening up the construction for new quantum resistant cryptographic schemes. The latter is called Learning Rank with Errors (LRE) and can be seen as an adaptation of the LPN problem to the rank metric setting. In addition, we describe HBLRE, an HB-like authentication protocol that constitutes an application of the aforementioned problem. We also prove that HTLRE is secure against passive attacks and compare its parameters to those of the initial HB scheme.
Quantum security most commonly encompasses only offline passive quantum attacks, where a quantum computer is used by an adversary to solve some computationally hard problem, e.g. factoring or discrete logarithm. However, we are witnessing major efforts for the development and deployment of quantum communication networks, and in this environment, cryptographic protocols may also be implemented in quantum devices. In this new setting, a wider range of online active attacks may become possible, for example against targets that may, either deliberately or inadvertently, run a cryptographic scheme in superposition. In this work, we demonstrate that authentication protocols whose security is based on the difficulty of learning linear functions subject to errors may be vulnerable to attacks where adversaries can make queries in superposition — that is, under the so-called “Q2” adversarial model. We do so by describing superposition attacks against a family of symmetric-key authentication protocols based on the LPN problem, a post-quantum cryptography assumption. Our attacks against the HB+ and HB# protocols, both of which have classical proofs of security against active attacks, are based on the Bernstein-Vazirani algorithm, and can efficiently recover the secret key. Despite being conceptually simple, we suggest that our attack techniques might be extended and adapted to also allow for superposition attacks against some modern lattice-based identification and post-quantum signature schemes.
The Learning with Errors (LWE) problem is a special average-case lattice problem, which has proved to be as hard as worst-case lattice problems. By this property, it has become the cornerstones for a series of cryptographic applications under the security assumption of worst-case lattice problems. However, the efficiency of these applications are not high. Therefore, how to improve the efficiency of cryptographic applications based on LWE is an urgent problem to be solved. In this paper, a new variant of LWE is proposed. By using trapdoor composed by lattice-based matrix and its dual orthogonal matrix, we construct a more efficient public key encryption (PKE) scheme based on the variant. Furthermore, by the hardness of the variant problem, we prove the new PKE scheme is chosen plaintext attack (CPA) secure. At last, we analyze the homomorphism property of the new PKE scheme.
We introduce Learning with Correlated Errors (LCE), a new lattice-based computationalhardness assumption in which observed samples carry noise generated by a low-rank linearcorrelation structure. Formally, given samples (A, b = As + Ce0 + e1 mod q), whereC ∈ Zm×rq is a publicly known correlation matrix and e0, e1 are short Gaussian vectors, thetask is to recover the secret s.Unlike LWE, the noise in LCE is globally correlated: up to r independent root noise sourcesdrive m observations simultaneously. Unlike the recent hybrid sparse-small assumptions ofGhosal et al. [GJL+25], LCE preserves a lattice structure that enables a reduction from theLearning with Errors (LWE) problem, thereby inheriting its worst-case hardness guarantees.We prove: (1) Worst-case hardness via reduction: We give a polynomial-timereduction from Decision-LWE to Decision-LCE, establishing that LCE is at least as hardas LWE and thereby inheriting its worst-case lattice hardness guarantees. (2) Search-to-Decision reduction: Search-LCE and Decision-LCE are polynomial-time equivalent (viaan explicit n-hybrid argument). (3) Cryptographic construction: an IND-CPA-securepublic-key encryption scheme from Decision-LCE. (4) Quantum resistance: by composingour reduction with Regev’s quantum reduction, we show that LCE resists known quantumattacks, with quantum lattice sieving requiring an estimated 20.265n quantum gates (matchingthe estimated cost for standard LWE).LCE provides a new, independently motivated hardness foundation for post-quantumcryptography and adds meaningful assumption diversity beyond LWE and LPN.
The rapid development of quantum computers poses a significant threat to the majority of current authenticated key exchang protocols, designed on the hardness of large integer factorization and discrete logarithm problems. Therefore, it is imperative to develop secure and efficient quantum-resistant authenticated key exchang protocols. This paper designs a new public-key cryptographic scheme for identity authentication based on Ring Learning With Errors (RLWE) problem and error reconciliation mechanism. Based on the scheme, we further design a quantum-resistant authenticated key exchange protocol (AKE). This protocol is provably secure under the standard eCK model and achieves forward secrecy. Compared with other classic key exchange protocols based on the RLWE problem, our protocol shows comprehensive advantages in terms of security, computational complexity, and communication complexity.
The swift advancement of quantum computing devices holds the potential to create robust machines that can tackle an extensive array of issues beyond the scope of conventional computers. Consequently, quantum computing machines create new risks at a velocity and scale never seen before, especially with regard to encryption. Lattice-based cryptography is regarded as post-quantum cryptography’s future and a competitor to a quantum computer attack. Thus, there are several advantages to lattice-based cryptographic protocols, including security, effectiveness, reduced energy usage and speed. In this work, we study the learning with errors (LWE) problem and the cryptosystems that are based on the LWE problem and, in addition, we present a new efficient variant of LWE cryptographic scheme.
This paper, proposes a novel undeniable signature scheme based on the ring learning with errors (RLWE) problem, a complex lattice problem. In our scheme, authentic signatures can be validated via an interactive protocol, which guarantees that adversaries cannot forge signatures. Moreover, it ensures that honest participants consistently finish the verification procedure. Thus, the scheme is a strong and effective quantum-resistant undeniable signature scheme. Our security analysis, demonstrates resilience against both classical and quantum adversaries, based on the RLWE problem's hardness assumptions. Additionally, the random Oracle model is utilised to evaluate our protocol's security, showing that our scheme satisfies important cryptographic properties like completeness, soundness, and unforgeability. Our work advances the feasibility of post-quantum undeniable signature schemes for real-world cryptographic applications.