Security Improvement On Chien Et Al.´s Remote User Authentication Scheme Using Smart Cards

A smart card based scheme is very practical to authenticate remote user. In 2002, Chien-Jan-Tseng proposed a mutual authentication scheme using smart card. But in 2004, Ku-chen pointed out the weaknesses of Chien et al´s scheme and proposed an improvement to Chien et al.´s scheme to prevent from some weaknesses. However, Hsu pointed out there is still susceptible to parallel session attack in Ku-Chen´s scheme. Later, Chien et al.´s indicated there is another weakness in Ku-Chen´s scheme and made an enhancement to resolve such problems. But we find Chien et al.´s scheme can´t resist parallel session attack too. In this paper, we make a modification of Chien et al.´s scheme to resolve the problem