Paper 2025/481

RHQC: post-quantum ratcheted key exchange from coding assumptions

Julien Juaneda , TéSA, Fédération ENAC ISAE-SUPAERO ONERA, University of Toulouse
Marina Dehez-Clementi, Fédération ENAC ISAE-SUPAERO ONERA, University of Toulouse
Jean-Christophe Deneuville, Fédération ENAC ISAE-SUPAERO ONERA, University of Toulouse
Jérôme Lacan, Fédération ENAC ISAE-SUPAERO ONERA, University of Toulouse
Abstract

Key Exchange mechanisms (KE or KEMs) such as the Diffie-Hellman protocol have proved to be a cornerstone conciliating the efficiency of symmetric encryption and the practicality of public key primitives. Such designs however assume the non-compromission of the long term asymmetric key in use. To relax this strong security assumption, and allow for modern security features such as Perfect Forward Secrecy (PFS) or Post Compromise Security (PCS), Ratcheted-KE (RKE) have been proposed. This work proposes to turn the Hamming Quasi-Cyclic (HQC) cryptosystem into such a Ratcheted-KE, yielding the first code-based such construction. Interestingly, our design allows indifferently one party to update the key on-demand rather than the other, yielding a construction called bi-directional RKE, which compares favorably to generic transformations. Finally, we prove that the resulting scheme satisfies the usual correctness and key-indistinguishability properties, and suggest concrete sets of parameters, assuming different real-life use cases.

Note: Submitted to an International Conference, currently under review.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint.
Keywords
Ratcheted Key ExchangeCodingPerfect Forward SecrecyPost-Compromise SecurityPost-Quantum
Contact author(s)
julien juaneda @ isae-supaero fr
marina dehez-clementi @ isae-supaero fr
jean-christophe deneuville @ enac fr
jerome lacan @ isae-supaero fr
History
2025-03-14: approved
2025-03-13: received
See all versions
Short URL
https://ia.cr/2025/481
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2025/481,
      author = {Julien Juaneda  and Marina Dehez-Clementi and Jean-Christophe Deneuville and Jérôme Lacan},
      title = {{RHQC}: post-quantum ratcheted key exchange from coding assumptions},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/481},
      year = {2025},
      url = {https://eprint.iacr.org/2025/481}
}
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