Implementation of Revocable Group Signatures with Compact Revocation List Using Vector Commitments

Group signature schemes allow members to anonymously sign messages on behalf of the group. In this scheme, an efficient membership revocation is one of the important issues. The scheme proposed by Libert et al. has achieved O(1) signature and membership certificate size, O(1) signing and verification times, and O(log N) public key size, where N is the total number of members. However the Revocation List (RL) data is large, due to O(R) signatures in RL, where R is the number of revoked members. Recently, the extended scheme was proposed by reducing the RL size to O(R/T) using a vector commitment to compress revocation entries, where T is the number of compressions, while O(1) membership certificate size remains. However, this scheme has not been implemented yet, and the practicality on the computation times for concrete T is unknown. In this paper, we implemented the scheme and explore the practicality. From the experimental results, the signing time is less than 500 ms for T = 400, but the verification time is about 1.5 s. We consider that the implemented scheme is practical in a mobile environment due to lower user computation time and storage.