Cryptanalysis of a password authentication scheme over insecure networks

The security of a password authentication scheme using smart cards proposed by Liao et al. [I.-E. Liao, C.-C. Lee, M.-S. Hwang, A password authentication scheme over insecure networks, J. Comput. System Sci. 72 (2006) 727–740] is analyzed. Three kinds of attacks are presented in different scenarios.