Cryptanalysis of the User Authentication Scheme with Anonymity

Nowadays, wireless communications using mobile device are growing rapidly. The most advantage of wireless communication is that user can transfer various information to anywhere at anytime using mobile device. However, it is clear that security of the wireless communications is more complex than wired owing to the openness of the wireless network. Thus, authentication has become the most important issue in the wireless communication. Furthermore, owing to the fact that location information shows user's life style, user anonymity becomes also significant issue. Recently, in 2011, Kang et al. pointed out that Wu et al.'s scheme has some security vulnerabilities and proposed an improved scheme. However, in this paper, we discuss that Kang et al.'s scheme is still vulnerable to active adversary.