Speeding Up Revocable Group Signature with Compact Revocation List Using Vector Commitments

抄録

In ID-based user authentications, a privacy problem can occur, since the service provider (SP) can accumulate the user's access history from the user ID. As a solution to that problem, group signatures have been researched. One of important issues in the group signatures is the user revocation. Previously, an efficient revocable scheme with signing/verification of constant complexity was proposed by Libert et al. In this scheme, users are managed by a binary tree, and a list of data for revoked users, called a revocation list (RL), is used for revocation. However, the scheme suffers from the large RL. Recently, an extended scheme has been proposed by Sadiah and Nakanishi, where the RL size is reduced by compressing RL. On the other hand, there is a problem that some overhead occurs in the authentication as a price for reducing the size of RL. In this paper, we propose an extended scheme where the authentication is speeded up by reducing the number of Groth-Sahai (GS) proofs. Furthermore, we implemented it on a PC to show the effectiveness. The verification time is about 30% shorter than that of the previous scheme by Sadiah and Nakanishi.