Paper 2024/117

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

Alex Pellegrini, Eindhoven University of Technology
Giovanni Tognolini, University of Trento

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.

Available format(s)
Attacks and cryptanalysis
Publication info
post-quantum cryptographycode-based cryptographyuniversal forgery attack
Contact author(s)
alex pellegrini @ live com
giovanni tognolini @ unitn it
2024-01-29: approved
2024-01-26: received
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      author = {Alex Pellegrini and Giovanni Tognolini},
      title = {Breaking HWQCS: a code-based signature scheme from high weight QC-LDPC codes},
      howpublished = {Cryptology ePrint Archive, Paper 2024/117},
      year = {2024},
      note = {\url{}},
      url = {}
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