An Improved Group Signature Scheme with Application in Privacy Protection of Alliance Chain

Currently, privacy protection in consortium blockchains can be categorized into two primary schemes based on their characteristics. The first is the ring signature scheme, which renders the user identity completely anonymous. The second is the group signature scheme, where the user identity can be fully traced by the trusted authority (OA) in the event of a transaction dispute. To address the imbalance between privacy and accountability in consortium blockchain transactions, this paper introduces an enhanced multi-Key Generation Center (multi-KGC) group signature scheme tailored for consortium chains. We validate the anonymity and unforgeability of the proposed scheme through a security game. The enhanced group signature algorithm employs the Groth-Sahai proof system for non-interactive zero-knowledge proofs (NIZK) and leverages elliptic curve cryptography combined with threshold cryptography for key generation. This scheme is implemented within the Hyperledger Fabric consortium chain environment, and both computational and communication overheads are thoroughly analyzed. Experimental results indicate that, while the signature generation efficiency of the proposed scheme is slightly reduced compared to existing group signature schemes, its verification efficiency aligns with similar schemes. Functionally, our scheme facilitates a tiered disclosure of signing user information based on transaction values during transaction audits in consortium blockchain transactions.