Further improvement of an efficient password based remote user authentication scheme using smart cards

Recently, Ku-Chen proposed an improvement to Chien et al.´s scheme to prevent from some weaknesses. However, the improved scheme is not only still susceptible to parallel session attack, but also insecure for changing the user´s password in password change phase. Accordingly, the current paper presents an enhancement to resolve such problems. As a result, the proposed scheme enables users to change their passwords freely and securely without the help of a remote server, while also providing secure mutual authentication.