Security analysis of smart card based password authentication schemes

In the last few years, researchers have extensively studied the key exchange protocol. In 2007, Kwon et al. proposed a simple three-step key exchange protocol using smart card. In 2008, Chen and Lee proposed a secure and efficient user authentication scheme using smart card that is modified to enhance the security of the series of the Peyravian-Zunic scheme. The current paper demonstrates the vulnerability of Kwon et al.´s protocol regarding off-line password guessing attack and forgery attack. Also, we show that Chen and Lee´s scheme is still vulnerable to the off-line password guessing attack and has the non-reparability. In this paper, in addition, after analyzing the two protocols, we propose each of countermeasure against our attacks.