There is an ever increasing need of identity authentication in our daily life, from making purchase online and unlocking personal devices to accessing secure premises. Although physical lock, PIN and gesture (which is common for mobile devices) offer convenient solutions, only biometrics based authentication can provide the ultimate means of validating the identity credential. The use of biometric authentication entails many questions, especially when it is used over a long period of time and in different locations: Will the system performance degrade over time? How will its performance be affected by different acquisition environments, such as the office environment, public locations, and outdoor?