Abstract: As existing schemes only support coarse-grained attribute protection policies in differentiated privacy protection scenarios,an identity authentication privacy protection scheme based on multi-level commitment protocol(Iascb-Mcp) is proposed in this paper,which aims to allow users to selectively disclose or keep secret their attribute information according to requirements,so as to meet the protection requirements in different privacy scenarios.The scheme realizes the protection of user attributes through multi-level commitment structure.First,each user attribute is assigned a privacy level,and the corresponding commitment protocol is designed according to the privacy level.Secondly,different authentication methods are adopted according to the user attributes of different privacy levels,and zero-knowledge proof is used to ensure that the user's high privacy attributes can still be effectively authenticated without being exposed.Finally,the Iascb-Mcp scheme is used to construct a system based on al-liance chain authentication,which solves the privacy authentication of off-chain user attributes and the security of transactions between different groups on the chain.The results of security analysis and experiment show that other users cannot obtain the high privacy attribute of the prover in the authentication process.Compared with the group signature scheme,the authentication time of Iascb-Mcp is reduced to 1s to 3 s.Compared with the two-ring signature scheme,the newly generated proof file is about one-tenth of the size of the original file.

Key words: Blockchain, Zero-knowledge proof, Commitment agreement, Identity authentication, Privacy protection