An improved bilinear pairing based remote user authentication scheme

Recently Das et al. proposed a novel remote user authentication scheme using bilinear pairings. Chou et al. identified a weakness in Das et al.'s scheme and made an improvement. In this paper, we show that both Das et al.'s and Chou et al.'s schemes are insecure against forgery and replay attacks. We proposed an improved scheme that overcomes the security flaws without affecting the merits of the original scheme.