Paper 2026/1240
Adaptive attacks on FESTA variants with masked-degree isogenies
, Mitsubishi Electric (Japan)Abstract
FESTA is an isogeny-based trapdoor function proposed as a high-performance alternative in isogeny-based cryptography. Its core design principles have inspired a number of related constructions, collectively referred to as FESTA variants. The MOXZ attack is an adaptive attack that exploits malicious ciphertexts together with access to a checking oracle, aiming to compromise FESTA and its variants. This attack applies to FESTA variants whose secret keys are derived from isogenies of known degree; however, it does not extend to variants employing masked-degree isogenies. In this work, we present a novel adaptive attack that generalizes the MOXZ attack. Our attack successfully targets several FESTA variants even when their secret keys are isogenies of masked degree. We also identify POKE-4D as an exception for which our attack does not appear to be applicable.
Metadata
- Available format(s)
-
PDF
- Category
- Attacks and cryptanalysis
- Publication info
- Preprint.
- Keywords
- isogeny-based cryptographyFESTAadaptive attackGPST attack
- Contact author(s)
- Moriya Tomoki @ bp mitsubishielectric co jp
- History
- 2026-06-11: approved
- 2026-06-11: received
- See all versions
- Short URL
- https://ia.cr/2026/1240
- License
-
CC BY
BibTeX
@misc{cryptoeprint:2026/1240,
author = {Tomoki Moriya},
title = {Adaptive attacks on {FESTA} variants with masked-degree isogenies},
howpublished = {Cryptology {ePrint} Archive, Paper 2026/1240},
year = {2026},
url = {https://eprint.iacr.org/2026/1240}
}
