[Resource Topic] 2024/117: Breaking HWQCS: a code-based signature scheme from high weight QC-LDPC codes

Welcome to the resource topic for 2024/117

Title:
Breaking HWQCS: a code-based signature scheme from high weight QC-LDPC codes

Authors: Alex Pellegrini, Giovanni Tognolini

Abstract:

We analyse HWQCS, a code based signature scheme presented at ICISC 2023, which uses quasi-cyclic low density parity check codes (QC-LDPC). The scheme introduces high Hamming weight errors and signs each message using a fresh ephemeral secret key rather than using only one secret key, so to avoid known attacks on QC-LDPC signature schemes.
In this paper, we show that the signatures of HWQCS leak substantial information concerning the ephemeral keys and formally describe this behaviour. Furthermore, we show that for each security level, we can exploit the leakage to efficiently reconstruct partial secret data from very few signatures, and finally mount a universal forgery attack.

ePrint: https://eprint.iacr.org/2024/117

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