An improved group signature scheme

Abstract

As a special digital signature, a group signature scheme allows a group member to sign message on behalf of the group in an anonymous and unlinkability way, In case of a dispute, a designated group manager can reveal the actual identity of the signer. Anonymity and unlinkability are basic properties of group signature, which distinguish other signature schemes. Recently, based on a variant of Nyberg-Rueppel signature and knowledge proof signature, A.Miyaji et al proposed a new group signature scheme over only known-order group and claimed that the scheme is secure. Unfortunately, in this work we first show that the scheme has linkability, Namely, any one can distinguish whether two different group signatures are produced by the same signer, then give the corresponding attack on the scheme. Finally, we propose an improved scheme to overcome the above drawback:linkability and include a novel concept individual revocation of signatures. At the same time, we give the security analysis of the improved scheme. © Springer-Verlag Berlin Heidelberg 2005.