Weakness in ID-based one round authenticated tripartite multiple-key agreement protocol with pairings

In this paper, we show that the ID-based tripartite authenticated multiple-key agreement protocol by Liu et al. [ID-based tripartite key agreement protocol with pairing, 2003 IEEE International Symposium on Information Theory, 2003, pp. 136-143, or available at Cryptology ePrint Archive, Report 2002/122] is insecure against an unknown key-share attack. And then we propose a more efficient ID-based tripartite authenticated multiple-key agreement protocol to overcome the attack.