Introduction
Biometrics is defined as an automated method of verifying or recognizing the identity of a living
person based on physiological or behavioral characteristics [1]. While much research has been
done both to determine which traits can differentiate humans and to optimize that differentiation, the
problem of determining if the presented trait originates from a living person has received relatively
less attention. Between acquiring biometric data and delivering a result, there are various points
where the overall security of a biometric access system can be compromised.