The traditional authentication system is based on the secret key, and is mainly based on public key infrastructure （PKI）. Unfortunately, a key has many disadvantages, for example, the key can be forgotten or stolen, and can be easily cracked. Nowadays, authentication systems using biometric technology have become more prevalent because of the advantages over password-based authentication systems. In this article, several biometfic authentication models are presented, upon which most biometric authentication systems are based. Biometric authentication systems based-on these models provide high security for access control in non-face-to-face environment such as e-commerce, over open network.
