Expressive Dynamic Threshold Attribute-Based Anonymous Credentials With Succinct Showing
Threshold attribute-based anonymous credentials improve the security of traditional credentials systems by distributing the power of credential issuance across multiple independent issuers, and have attracted widespread attention, particularly for decentralized systems such as blockchain. However, existing solutions still exhibit shortcomings in terms of scalability, security, flexibility, and practicality. In this paper, we introduce EDT-ABC, an expressive dynamic threshold attribute-based anonymous credential system with succinct showing. Specifically, EDT-ABC allows each issuer to generate the secret key independently without relying on distributed key generation protocols or a trusted party. The thresholds can be dynamically adjusted, enabling verifiers to flexibly define thresholds for different services. Meanwhile, EDT-ABC achieves more expressive and practical selective disclosure by supporting non-possession proofs. By putting forth two novel primitives called universal set commitments and structure-preserving multi-signatures on equivalence classes with randomizable tags, which may both be of independent interest, we design a generic construction of EDT-ABC with provable security and provide an efficient instantiation. Comprehensive performance evaluation on personal computer and Raspberry Pi demonstrates that, compared to existing solutions, our EDT-ABC decreases the running time for issuing and showing the credentials by at least 67.44% and 28.78%, respectively, while achieving a token size reduction of over 82.10%.