Practical Delegatable Anonymous Credentials From Equivalence Class Signatures

Anonymous credentials (ACs) systems are a powerful cryptographic tool for privacy-preserving applications and provide strong user privacy guarantees authentication access control. ACs allow users to prove possession of attributes encoded in credential without revealing any information beyond them. A delegatable AC (DAC) system is an enhanced that allows the owners delegate obtained other users. This model hierarchies as usually encountered within public-key infrastructures (PKIs). DACs also stronger than traditional since identities issuers delegators can be hidden. In this paper we present novel DAC scheme supports attributes, provides anonymity delegations, restrict further comes with efficient construction. Our approach builds on new primitive call structure-preserving signatures equivalence classes updatable commitments (SPSEQ-UC). The high-level idea use special signature sign vectors set commitments, where extended by additional commitments. Signatures additionally include user's public key, which switched. us efficiently realize delegation DAC. Similar conventional SPSEQ, messages publicly randomized thus unlinkable showings system. We optimizations such cross-set commitment aggregation that, combination, enable selective showing using costly zero-knowledge proofs. instantiation proven secure generic group finally demonstrate practical efficiency our presenting performance benchmarks based implementation.