Efficient Attributes for Anonymous Credentials

The authors extend the Camenisch-Lysyanskaya anonymous credential system such that selective disclosure of attributes becomes highly efficient. The resulting system significantly improves upon existing approaches, which suffer from a linear complexity in the total number of attributes. This limitation makes them unfit for many practical applications, such as electronic identity cards. Their system can incorporate an arbitrary number of binary and finite-set attributes without significant performance impact. Their approach folds all such attributes in a single attribute base and, thus, boosts the efficiency of all proofs of possession. The core idea is to encode discrete binary and finite-set attribute values as prime numbers. They use the divisibility property for efficient proofs of their presence or absence.