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Group key agreement (GKA) protocols are used to secure group communications in wireless networks but most current GKA protocols do not consider privacy protection. GKA protocols for wireless networks should also handle dynamic group membership events such as user join and leave events. The Join and Leave Protocols provide backward and forward secrecy respectively, that is, the Join Protocol must ensure that a new user cannot obtain the previously established group key(s) and access the corresponding group communications (backward secrecy) while the Leave Protocol must ensure that a leaving user cannot obtain subsequent group key(s) and access new group communications (forward secrecy). Most recently, Wan et al proposed three anonymous ID-based GKA protocols, namely Initial GKA, Join and Leave Protocol, for wireless networks. We first show in this paper that their proposed Join and Leave Protocols do not provide backward and forward secrecy (as claimed) respectively. We also highlight the anonymity issues in their Join and Leave Protocols. We then propose three improved anonymous ID-based GKA protocols (Initial GKA, Join and Leave Protocol).