Security analysis of the improved group signature
Jianhong Zhang, Chen Xiaofeng, Wang Yumin · 2004
We show that the improved group signature (Yuh-Min Tseng and Jinn-ke Jan, Electron. Lett., vol.35, no.16, p.1324, 1999) has an essential flaw: universal forgery. An adversary can forge a group membership certificate to sign any message without being traced by the group manager.