A Two-Party Collaborative Blind Signature Scheme Based on SM9

The SM9 algorithm, established as a national cryptographic standard (GM/T 0044-2016), is an identity-based public key cryptographic technology that includes algorithms for data encryption/decryption, key encapsulation, digital signatures, etc. Addressing the issues of private key leakage and centralized signing authority in the national SM9 signature scheme, and avoiding complex key management, this paper proposes a two-party collaborative blind signature scheme based on SM9. The scheme involves the message owner using a blind factor to blind the message for signing, then the two parties with signing authority jointly complete the digital signature on the blinded message. During the signing interaction, neither the plaintext of the message to be signed nor the SM9 signing private key is disclosed, significantly resolving the security issues of the signing private key in SM9 blind signatures. The verification of this co-signature scheme not only ensures the time of verification computation but also guarantees the correctness, universality, and standardization of the signature verification algorithm.