Cryptanalysis of a remote user authentication scheme based on bilinear pairing

Remote user authentication scheme is a mechanism which allows a server to authenticate a remote user over insecure channel. Recently, Goriparthi et al. made an enhancement based on Das et al.'s remote user authentication scheme using bilinear pairings. The scheme has the merits of no verification table, freely changing password and preventing the forgery attack and the replay attack. This paper, however, demonstrates that Goriparthi et al.'s improved scheme is vulnerable to the insider attack, the denial-of-service attack, and the server spooling attack.