Implementation and Evaluation of an Pairing-Based Anonymous Credential System with Constant-Size Proofs and Efficient Proof Generations

To enhance user privacy, anonymous credential systems allow the user to convince a verifier of the possession of a certificate issued by the issuing authority anonymously. In the systems, the user can prove logical relations on his/her attributes embedded into the certificate. Previously, we proposed a pairing-based system with constant-size proofs. In the system, the proof generation needs only multiplications depending on the size of the proved relations, and it is more efficient than other existing system that needs the exponentiations whose costs are much larger than multiplications. However, our efficient system has never been implemented, and thus the practicality is not evaluated. In this study, we implemented the system, and measured the processing times and data size, when changing the parameters describing the size of the proved relation. The verification time is very fast and constant, and the proof size is also constant, from which we can confirm the practicality. However, the proof generation time increases, when the parameters increase. Although we confirm the practicality in case of small relations, we clarify the problems in case of larger relations, which should be solved in our future works.