Cryptanalysis of Tseng-Wu group key exchange protocol

Recently, Tseng and Wu pointed out that the second pro-tocol of Biswas's two-party keys scheme based on the Diffe-Hellman technique has a security weakness and pro-posed a new protocol to remedy the weakness. In this article, we point out that Tseng-Wu's protocol is vulner-able to a man-in-the-middle attack. An attacker could intercept, delete, or modify the communicated messages between two communicating party or among the group members.