DcDID: Highly privacy-secure decentralized identity system based on dynamic committee

The proposed self-sovereign identity satisfies the decentralized nature of blockchain. It ensures that users have complete control over their personal information. While decentralized identity systems have made great strides in guaranteeing credential uniqueness and securing user information, most existing systems are based on static committees. For decentralized identity systems on the blockchain, the committee nodes usually are made up of honest nodes on the chain. Nodes on the blockchain may join or quit at any time, so ignoring the dynamic changes of committee nodes can pose a severe threat to users' information security. In this paper, a decentralized identity system is proposed, based on dynamic committees(DcDID). The protocols in the system are constructed based on dynamic committee. A new contextual credential issuance protocol is constructed in the DcDId system. The protocol uses dynamic secret sharing techniques to store pairs of DIDs in the committee. This approach ensures the uniqueness of the credentials and dramatically improves the security of the user's private information during the dynamic change phase of the committee. Moreover, a new key recovery protocol is constructed in the DcDID system. In this protocol, asymmetric binary polynomial technique is used to change the secret sharing threshold. This approach ensures the security of the user's private key during the dynamic change phase of the committee. The security analysis included in this paper shows that DcDID significantly improves user privacy security compared to static committee-based systems. Our experimental results also show that our proposed protocol is feasible.