Abstract: Xie and Yu (2005) proposed a group signature scheme and claimed that it is the most efficient group signature scheme so far and secure. In this paper, we show that two dishonest group members can collude to launch two attacks on the scheme. In the first attack they can derive the group secret key and then generate untraceable group signatures. In the second attack, they can impersonate other group members once they see their signatures. Therefore we conclude that the signature scheme is not secure. We show that some parameters should be carefully selected in the scheme to resist our attacks.

Key words: Group signature, Colluding attack, Factoring problem

Please provide your name, email address and a comment

Your Name: Affili: E-Mail Address:

Comment (Please comment in English):


Verification Code(click to change a pic):