Issuer-Revocable Issuer-Hiding Attribute-Based Credentials Using an Accumulator

Attribute-based credential (ABC) system allows a user to anonymously prove his/her attributes to a verifier, using a credential issued by an issuer. In the conventional ABC systems, since the verifier knows who is the issuer from the attribute proof, the information on the issuer can reveal some attributes of the user. Thus, an issuer-hiding $ABC$ was recently proposed, where the issuer's ID (and the issuer's public key) is hidden. However, in the previous system, the verifier decides the accepted issuers and issues the signatures on the issuers' public keys to each user in advance, and thus the computational and communication costs depending on the number of issuers are required whenever an issuer is revoked. In this paper, we propose an issuer-revocable issuer-hiding ABC system that is extended from the previous system. In the proposed system, the verifier generates and issues the signatures of the issuers' public keys once. Then, whenever an issuer is revoked, the verifier sends only a short revocation list using a pairing-based accumulator to each user.