User Authentication Schemes for Mobile and Handheld Devices

User authentication is a difficulty for every system providing safe access to precious, private information, or personalized services. It is a continual problem, particularly with mobile and handheld devices such as Personal Digital Assistants (PDAs). User authentication is the primary line of defence for a handheld device that comes into the hands of an unauthorized individual. Password or Personal Identification Number (PIN) based authentication is the leading mechanism for verifying the identity of actual device users but this method has been shown to have considerable drawbacks. For example, users tend to pick PIN or passwords that can be easily guessed. On the other hand, if a password is hard to guess, then it is often hard to remember. To address this problem in handheld devices, some researchers have developed comparatively more secure, affordable and memorable authentication schemes based on graphical assistance, images and audio. In this paper, we conduct a comprehensive survey and analysis of such existing user authentication schemes for mobile and handheld devices. The complete analysis of these schemes in term of usability and security are also discussed in this paper. This paper will be useful for information security researchers and practitioners who are interested in finding an alternative to password based authentication schemes.