In the last several decades, computers or automated technologies have been utilized to verify the identity of humans using biometrics (i.e., physical and behavioral characteristics) (Wayman, Jain, Maltoni, & Maio, 2004), as it often surpasses the conventional automatic identity verification measures like passwords and personal identification numbers (PINs) by offering positive human identification. For example, the use of a PIN actually denotes the automatic identification of the PIN, not necessarily identification of the person who has provided it. The same applies with cards and tokens, which could be presented by anyone who successfully steals the card or token. PINs and passwords also have the problem of being compromised by ‘shoulder surfing’ and people picking the obvious choices. Even the recently proposed graphical passwords share similar problems.