Security improvements on an efficient group key agreement protocol

Group key agreement protocols are important for collaborative and group-oriented applications,which enable group members to share a common conference key for secure group communication. Jung[1] proposed an efficient group key agreement protocol which does not need public key cryptosystems and can be applied in dynamic group applications. But not long ago Lee[2] found inside attack can disrupt group key establishment in Jung´s scheme. In this paper, we propose two security improvements on Jung´s scheme, which can trace malicious attack and malicious members, and does not leak sensitive information of the group. The purpose of the improvements are not to get the malicious out of the group, but to be tolerant of the existence of malicious members and the group key can still be established in the group.