Security Analysis of Two Remote User Authentication Schemes Using Bilinear Pairings

Recently, Das et al. and Tseng et al. proposed a remote user authentication scheme using bilinear pairings, respectively. They can provide a flexible password change option to the users without any help from the remote server. However, some weaknesses of the two bilinear pairing based remote password authentication schemes are found in the paper. The schemes suffer from offline password guessing attack and impersonation attacks.