Abstract:

With the rapid development of quantum computing technologies, traditional digital signature schemes based on large integer factorization and discrete logarithm problems are facing potential security risks. Code-Based cryptographic systems, whose security relies on computationally hard problems such as syndrome decoding, are widely regarded as an important approach toward post-quantum cryptography. However, existing code-based signature schemes still provide relatively limited support for deniable semantics.To address this issue, this paper proposed a deniable ring signature scheme based on the HQC code structure. The proposed construction systematically adapted Stern-Like Σ protocols, OR composition, and the Fiat-Shamir transformation to the linear consistency relation induced by HQC public keys, and used this relation as the underlying statement of the zero-knowledge proof. On this basis, a signature-context-based tag binding mechanism was further introduced, through which signer confirmation and non-signer disavowal algorithms were incorporated as independent layers into the ring signature structure, thereby achieving complete deniable semantics. Finally, under the random oracle model, the unforgeability, anonymity, traceability, and non-frameability of the proposed scheme were analyzed, and its computational cost, communication overhead, and functional properties were evaluated. The analysis results show that the proposed scheme can uniformly achieve ring anonymity and deniable semantics under security assumptions based on code-based hard problems. However, its signature length and computational cost are affected by the number of proof rounds and the response encoding length, making it more suitable for anonymous authentication scenarios with small ring sizes where post-quantum security and subsequent responsibility clarification are prioritized.

Key words: post-quantum cryptography, HQC, deniable ring signatures, Stern-Like Σprotocols, Fiat-Shamir transform