Robust Two-Party Password Based Authenticated Key Agreement Protocol

In 2005, Lee and Lee pointed out that Lee N.Y. et al.´s password based authenticated key agreement protocol is vulnerable to a man-in-the-middle attack, and then proposed an improvement to overcome the attack. The current paper, however, demonstrates that Lee and Lee´s password based authenticated key agreement protocol is still vulnerable to off-line password guessing attacks. We also propose an improvement to the protocol in order to overcome such attacks.