Identity-based authenticated key agreement protocol becomes more and more important, but some schemes have security flaws, and others have more computation cost. This paper describes the weakness of Q. Yuan's protocol, and proposes an improved protocol from this protocol and Smart's scheme, which satisfy all the security properties. And the analysis of the security and efficiency was made.

We analyse the existing ID-based authenticated key agreement protocols, and find out that several proposed protocols of this type do not satisfy related security attributes. This paper reviews Wang's, He's and Guo's protocols sequentially, and shows key compromise impersonation attack on Wang's scheme, ephemeral secrets reveal attack on He's scheme, key reveal attack and ephemeral secrets reveal attack on Guo's scheme, respectively, Finally, this paper proposes some improving suggestions on corresponding weaknesses of these protocols. IntroductionThe first key agreement protocol was designed by Diffie-Hellman in 1976 [4], but it is not against man-in-middle attack. So a lot of improved protocols based on PKI (Public Key Infrastructure) were presented, which has high computation cost, too much storage efforts and communication bandwidth. In this case, Shamir proposed the ID-based cryptosystem [12] which calculates an entity's public key from his/her identity information. Afterwards, MQV protocol was presented to provide implicit authentication for each participate [10], which is known as the first authenticated key agreement protocol.The first ID-based authenticated key agreement protocol was proposed by Smart [14], but it did not satisfy the forward security attribute [13]. So a new protocol was published by Shim, which satisfied several desirable security attributes, but Sun pointed out it was not against man-in-middle attack [15]. From then on, a series of schemes [5] [6] [7] [9] [17] were presented in succession. However, some of these schemes have security flaws.