An Improvement on Hsiang and Shih´s Remote User Authentication Scheme Using Smart Cards

Recently, Hsiang and Shih proposed remote user authentication scheme using smart cards, they claims that their schemes defended against parallel session attack, and password guessing attacks. In this paper, we show that Hsiang and Shih´s schemes are still vulnerable to off-line password guessing attacks and undetectable on-line password guessing attacks. Notably, problems remain in situations where the user loses a smart card. To remedy these flaws, this paper proposes an improvement on Hsiang and Shih´s remote user authentication schemes using smart cards.