Post-quantum secure group signature with verifier local revocation and backward unlinkability

Abstract

Group signature supports users to generate signatures on behalf of the group. Verifier local revocation (VLR) is an important method to revoke a misbehaving user in group signature, which has attracted many researchers’ attention. However, the existing lattice-based group signature schemes with VLR either achieve only selfless anonymity, have revocation list of size linear with the number of revoked users, or suffer from the issue that signatures generated by revoked users could easily be linked by an adversary. Additionally, the development of quantum computing technology threatens the security of traditional cryptosystems. Therefore, in this paper we propose a new lattice-based group signature scheme, which makes use of the complete tree technique to combine the timestamp with VLR. It enjoys post-quantum security and satisfies almost full anonymity and traceability if the LWE and SIS problems are hard. Compared with previous schemes, our scheme achieves backward unlinkability additionally. Thanks to the revocation token update mechanism, a revocation token for time period t could not be connected with signatures generated in period t+1. Furthermore, the revocation list in our scheme only stores the tokens of users who have been revoked before the expiry, reducing the revocation list size effectively.