An Improvement of Remote Authentication and Key Agreement Schemes

[[abstract]]Recently, Shieh et al. have pointed out that Juang's password authenticated key agreement scheme and Chien et al.'s remote authentication scheme are vulnerable to some attacks. Therefore, they presented a modified protocol to avoid those attacks. However, the authors of this article shall show that Shieh et al.'s scheme and Juang's scheme have two weaknesses, respectively. Therefore, we shall improve the weaknesses of their schemes