Zemlyanika — Module-LWE based KEM with the power-of-two modulus, explicit rejection and revisited decapsulation failures

Alexey S. Zelenetsky; Peter G. Klyucharev

Paper 2025/746

Zemlyanika — Module-LWE based KEM with the power-of-two modulus, explicit rejection and revisited decapsulation failures

Alexey S. Zelenetsky

, Bauman Moscow State Technical University, QApp

Peter G. Klyucharev, Bauman Moscow State Technical University

Abstract

This work introduces Zemlyanika, a post-quantum, IND-CCA secure key encapsulation mechanism based on the Module-LWE problem. Zemlyanika adopts a standard high-level design approach in which a passively secure public-key encryption scheme is upgraded to an actively secure key encapsulation mechanism via the Fujisaki–Okamoto transform. The scheme is characterized by three key design choices: a power-of-two modulus, explicit rejection, and revised bounds on the decapsulation failure probability. Employing a power-of-two modulus is uncommon in Module-LWE-based schemes, primarily due to the inapplicability of the Number Theoretic Transform (NTT). However, we argue that this choice offers several often underestimated advantages. We also use explicit rejection, which is more efficient than its implicit counterpart. Recent research shows that both approaches offer comparable security guarantees, and thus this choice does not compromise the scheme's overall security. Finally, we provide a rigorous analysis showing that the conventional upper bound on the decapsulation failure probability can be safely relaxed without weakening security. Increasing this bound yields measurable gains in both performance and resistance to Module-LWE–based attacks.

Note: This is a a preprint submitted to Journal of Computer Virology and Hacking Techniques

Metadata

Available format(s): PDF
Category: Public-key cryptography
Publication info: Published elsewhere. Journal of Computer Virology and Hacking Techniques
DOI: 10.1007/s11416-025-00576-y
Keywords: key encapsulation mechanism M-LWE explicit rejection decapsulation failure
Contact author(s): azelenetskiy @ qapp tech
pk iu8 @ yandex ru
History: 2025-09-29: last of 2 revisions; 2025-04-26: received; See all versions
Short URL: https://ia.cr/2025/746
License: CC BY

BibTeX

@misc{cryptoeprint:2025/746,
      author = {Alexey S. Zelenetsky and Peter G. Klyucharev},
      title = {Zemlyanika — Module-{LWE} based {KEM} with the power-of-two modulus, explicit rejection and revisited decapsulation failures},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/746},
      year = {2025},
      doi = {10.1007/s11416-025-00576-y},
      url = {https://eprint.iacr.org/2025/746}
}