Insider Forgery Cryptanalysis of Two Post-Quantum Multi-Signature Schemes

In 2010, M. Meziani and P.-L. Cayrel presented two post-quantum multi-signature schemes based on the syndrome decoding hard problem and error correcting codes. In this paper, we propose the insider forgery cryptanalysis of M. Meziani et al.s post-quantum multi-signature schemes. In M. Meziani et al.s schemes, the verifier only verifies the final multi-signature and does not check the validity of the partial signatures generated by other signers. Thus the malicious last signer can forge a valid multi-signature by himself/herself on behalf of the group of signers, which can pass the verification of the verifier. Therefore, M. Meziani et al.s post-quantum multi-signature schemes do not meet the security requirements of multi-signature schemes.