Issuer-Hiding Attribute-Based Credentials with Constant-Size Attribute Proofs for CNF Formulas with Negations

Abstract

Attribute-based credential (ABC) systems allow a user to anonymously prove attributes of the user to a verifier. In advance, the user is issued a credential of the attributes from an issuer. The user can select disclosed attributes, and prove the possession of the attributes without revealing other unnecessary attributes. However, the issuer’s public key is required in the verification of the attribute proof, and thus the verifier can know who is the issuer issuing the credential. An issuer-hiding ABC system was proposed, where the issuer can be hidden in the attribute proof, and the issuer’s attributes can be proved. Thus, the verifier can verify the anonymous issuer flexibly based on the issuer’s attributes. In this paper, we propose an issuerhiding ABC system by combining the previous system and an accumulator. In the proposed system, CNF formulas with negations can be used as the attribute proof. Since the attributes of the user and the issuer are accumulated, the constant proof size and verification time are achieved. We show the practicality by an implementation on a PC.