[Resource Topic] 2025/830: Simple Power Analysis Attack on SQIsign

Welcome to the resource topic for 2025/830

Title:
Simple Power Analysis Attack on SQIsign

Authors: Anisha Mukherjee, Maciej Czuprynko, David Jacquemin, Péter Kutas, Sujoy Sinha Roy

Abstract:

The isogeny-based post-quantum digital signature algorithm SQIsign offers the most compact key and signature sizes among all candidates in the ongoing NIST call for additional post-quantum signature algorithms. To the best of our knowledge, we present the first Simple Power Analysis (SPA) side-channel attack on SQIsign, demonstrating its feasibility for key recovery.
Our attack specifically targets secret-dependent computations within Cornacchia’s algorithm, a fundamental component of SQIsign’s quaternion module. At the core of this algorithm, a secret-derived yet ephemeral exponent is used in a modular exponentiation subroutine. By performing SPA on the modular exponentiation, we successfully recover this ephemeral exponent. We then develop a method to show how this leaked exponent can be exploited to ultimately reconstruct the secret signing key of SQIsign.
Our findings emphasize the critical need for side-channel-resistant implementations of SQIsign, highlighting previously unexplored vulnerabilities in its design.

ePrint: https://eprint.iacr.org/2025/830

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