A Text based Authentication Scheme for Improving Security of Textual Passwords

User authentication through textual passwords is very common in computer systems due to its ease of use. However textual passwords are vulnerable to different kinds of security attacks, such as spyware and dictionary attacks. In order to overcome the deficiencies of textual password scheme, many graphical password schemes have been proposed. The proposed schemes could not fully replace textual passwords, due to usability and security issues. In this paper a text based user authentication scheme is proposed which improves the security of textual password scheme by modifying the password input method and adding a password transformation layer. In the proposed scheme alphanumeric password characters are represented by random decimal numbers which resist online security attacks such as shoulder surfing and key logger attacks. In the registration process password string is converted into a completely new string of symbols or characters before encryption. This strategy improves password security against offline attacks such as brute-force and dictionary attacks. In the proposed scheme passwords consist of alphanumeric characters therefore users are not required to remember any new kind of passwords such as used in graphical authentication. Hence password memorability burden has been minimized. However mean authentication time of the proposed scheme is higher than the textual password scheme due to the security measures taken for the online attacks.