Analysis of two group signatures based on bilinear maps

Group signatures are broadly used to build E-voting, E-binding and fair E-cash systems. In 2004, Boneh et al proposed a short group signature (BBS04) and a group signature with verifier-local revocation (BS04). Both schemes are based on bilinear maps. In this paper, we revisit and improve them. The security of the revisited BBS04 scheme can be directly derived from the improved BS04. Our analysis is helpful to unveil the psychological activities during designing the two signatures. This will promote the techniques for analyzing cryptographic protocols.