Analysis and improvement of a new authenticated group key agreement in a mobile environment

In 2009, Lee et al. (Ann Telecommun 64: 735-744, 2009) proposed a new authenticated group key agreement protocol for imbalanced wireless networks. Their protocol based on bilinear pairing was proven the security under computational Diffie-Hellman assumption. It remedies the security weakness of Tseng's nonauthenticated protocol that cannot ensure the validity of the transmitted messages. In this paper, the authors will show that Lee et al.'s authenticated protocol also is insecure. An adversary can impersonate any mobile users to cheat the powerful node. Furthermore, the authors propose an improvement of Lee et al.'s protocol and prove its security in the Manulis et al.'s model. The new protocol can provide mutual authentication and resist ephemeral key compromise attack via binding user's static private key and ephemeral key.