Cryptanalysis of Xia–You group signature scheme

Abstract

Group signature is a variant of digital signatures, which allows members of a group to sign messages anonymously on behalf of the group. The application of group signatures includes e-voting, e-bidding and e-cash. Recently, Xia and You proposed an identity-based group signature scheme with strong separability. In this paper, however, we find that there are several problems in the Xia–You group signature scheme. This scheme is vulnerable to forgery attacks. Any adversary could easily forge a valid group signature for any message without the knowledge of the secret values of the legal members of the group. Furthermore, the Xia–You group signature scheme does not satisfy nearly all other security requirements of group signatures. The signatures are too long to be computed, stored and transmitted.