Abstract
Issuer-Hiding Anonymous Credential (IHAC) is a cryptographic primitive, which enables users to authenticate themselves with fine-grained control over their credentials (certified attributes), without revealing the credential issuers. A state-of-the-art IHAC scheme, designed for Self-Sovereign Identity systems, was recently published by Sanders and Traoré at PET’24. However, this scheme does not support the revocation of credentials. It is well-known that revocation is essential for many secure applications. In this work, we introduce a revocable IHAC scheme. Our contributions are three-fold. First, we use the classical pairing-based accumulator with Sanders and Traoré’s scheme to provide user revocation without compromising its unique features like compactness and issuer-hiding. Second, we prove the security of our construction under the well-studied q-Strong Diffie-Hellman (q-SDH) assumption, rather than the Generic Group Model (GGM) originally used by Sanders and Traoré. Third, our construction ensures optimal efficiency, as the accumulator-based revocation incurs only a small extra overhead to PET’24. Our implementation shows that when using 100 certified attributes and 20 issuers in an anonymous credential system, the Show \textsf{Show}{}{} and Verify \textsf{Verify}{}{} protocol takes 3.15 s in total, only incurring a 2.5% % increase compared to Sanders and Traoré’s scheme.