International Association
for Cryptologic Research

In remote authentication scheme, a remote user can communicate with server over open networks even though the physical distance is much far. Before interaction, they require to establish common session key by authenticating each other. Recently in 2014, Kumari et al. proposed the efficient scheme for remote user authentication. However in this paper, we show that the Kumari et al.\'s scheme is vulnerably susceptible to the Insider Attack, Stolen Verifier Attack, Session Key Disclosure Attack, Password Guessing Attack, Modification Attack, User Impersonation Attack, Replay Attack, Shoulder Surfing Attack and Denial of Service Attack. Afterwards, we have proposed an improved remote user authentication scheme to deal with these attacks and other attacks.