Multi-party post-quantum key exchange schemes

Parhat Abla

Group key exchange schemes allow group members to agree on a session key. Although there are many works on constructing group key exchange schemes, but most of them are based on algebraic problems which can be solved by quantum algorithms in polynomial time. Even if several works considered lattice based group key exchange schemes, believed to be post-quantum secure, but only in the random oracle model. In this work, we propose a group key exchange scheme based on ring learning with errors problem. On contrast to existing schemes, our scheme is proved to be secure in the standard model. To achieve this, we define and instantiate multi-party key reconciliation mechanism. Furthermore, using known compiler with lattice based signature schemes, we can achieve authenticated group key exchange with postquantum security.

Sitnikov, Konstantin

Akanksha Singh, Harish Chandra, Saurabh Rana

ABSTRACT In this paper, we introduce a lattice‐based authenticated three‐party key agreement scheme for mobile devices with the aim of achieving both post‐quantum security and efficiency. Our scheme is inspired by the authenticated key exchange protocol developed. We revisit the recently suggested system, which is a communication‐efficient three‐party password‐authenticated key exchange, in which we found that the scheme is not fully correct and also demonstrate that the scheme is not safe from user's anonymity and impersonation assaults. We provide an enhanced scheme that is both effective and resistant to the mentioned assault. We also demonstrate its security in a ROM (Random Oracle Model). A comparison analysis that includes performance, security evaluations, energy consumption, and packet loss rate is also provided, proving the suitability of the suggested design.

Julia Bobrysheva, Sergey Vladimirovich Zapechnikov

Yang Li, Rui-Rui Zhou

Sanish Gurung

Key establishment among multiple participants over an insecure channel is a widely adopted cryptographic operation. However, a quantum adversary can employ Shor's algorithm, compromising most key exchange protocols based on the discrete logarithm problem. Safeguarding against such quantum attacks requires transitioning to post-quantum key establishment protocols that incorporate quantum-resistant mathematical hardness assumptions. This thesis addresses the research gap on post-quantum key exchange for multiple participants and decentralized settings. It proposes the feasible solution, Multi-Party Key Exchange (MP-KEX) protocol, to derive a conference key, implemented and evaluated using OpenSSL and liboqs cryptographic libraries. The research evaluates four cryptographic algorithm combinations of key exchange and authentication, comparing their performance, identifying the protocol's bottleneck, and addressing the formulated research questions. This thesis demonstrates that the computational cost of MP-KEX protocol is largely dictated by digital signature algorithm used, with ML-DSA being inherently slower than ECDSA-P256. On the other hand, ML-KEM is computationally fast compared to X25519 for key exchange purpose. The main bottleneck of the protocol arises from the verification phase in the naive model, whose computation time is reduced by nearly 50 % with a quorum-based verification system when the group size is large. The findings demonstrate the feasibility of MP-KEX protocol, proposing novel post-quantum key exchange protocol that provides scalable performance and empirical comparison between classical and post-quantum approaches to contributory group key establishment.