Untraceability of Several Group Signature Schemes Yang Yue1,2 Ou Hai-wen 2 (1. College of Communication Engineering, Xidian University, Xi' an, 710071, China Abstract: A group signature scheme allows every member to sign message on behalf of the group in an anonymous fashion。In case of a dispute, group manager can trace the signer of a valid group signature. In the paper, we show the untraceability of several group signature schemes by new and very simple attack. Key Words: Group Signature, Traceability