Dynamic Decentralized Group Signature Scheme for Privacy Protection in Blockchain

Group signature schemes can play a key role in privacy protection of blockchain-based applications because of its security properties like unforgeability, anonymity, unlinkability, traceability, etc. But the malicious group manager may collude with some group members leading to biased decisions. This issue was addressed by Devidas et al. [12] with a static decentralized group signature scheme(DGSS) by decentralizing the group manager. However, the limitation of DGSS is that it works only for static domains, where group members are fixed and will not allow new members to join and existing members to leave the network. In this paper, DGSS is extended to propose a dynamic decentralized group signature scheme which allows the group members to join and revoke at run-time. The performance of Devidas et al. [12] scheme is also improved by reducing the number of multiplications to make it suitable for user identity privacy protection in lightweight blockchains or memory constraint devices. The security analysis and proof of correctness for the proposed scheme are also discussed in this paper.