An accurate automatic personal identification is critical to a wide range of application domains such as access control, electronic commerce, and welfare benefits disbursement. Traditional personal identification methods (e.g., passwords, PIN) suffer from a number of drawbacks and are unable to satisfy the security requirement of our highly interconnected information society. Biometrics refers to automatic identification of an individual based on her physiological or behavioral traits. While biometrics is not an identification panacea, it is beginning to provide very powerful tools for the problems requiring positive identification.