An ID-based authenticated group key agreement (AGKA) protocol allows a group of members to share a key and
provide an assurance of key sharing with an intended group with the user's identity, which is used for conferencing
environments. In 2004, Choi et al proposed an ID-based authenticated group key agreement with bilinear maps (also
called CHL protocols), which was extended from Burmester and Desmedt conference key agreement protocols.
Unfortunately, their protocols were found to be vulnerable to the insider attacks in which cases that the two malicious
users have the previous authentication transcripts of the party by Zhang, Chen and Shim. In this paper, we proposed an
improved ID-based AGKA. In our scheme, each session has a unique session identity which is published by Key
Generation Center. With such unique session identity binding to each session, our protocols can prevent the insider
attack. Especially, our protocols can not enhance the computationally cost and it is still efficient.