Cryptanalysis of an efficient certificateless two-party authenticated key agreement protocol

Recently, He et al. (Computers and Mathematics with Applications, 2012, 64(6): 1914-1926) proposed a new efficient certificateless two-party authenticated key agreement protocol. They claimed their protocol was provably secure in the extended Canetti-Krawczyk (eCK) model. In this paper, we will show that their protocol is insecure. A type I adversary, who obtains one party\u27s ephemeral private key, can impersonate the party to cheat the other party and compute the shared session key successfully. For overcoming this weakness, we also propose a simple countermeasure