Biometric recognition refers to the use of distinctive physiological and behavioral characteris-tics (e.g., fingerprints, face, hang geometry, iris, gait, signature), called biometric identifiers orsimply biometrics, for automatically recognizing a person. Questions such as “Is this personauthorized to enter the facility?”, “Is this individual entitled to access the privileged informa-tion”, and “Did this person previously apply for a job?” are routinely asked in a variety oforganizations in both public and private sectors. Because biometric identifiers cannot be easilymisplaced, forged, or shared, they are considered more reliable for person recognition thantraditional token- (e.g., keys) or knowledge- (e.g., password) based methods. Biometricrecognition can provide better security, higher efficiency, and increased user convenience. It isfor these reasons that biometric systems are being either increasingly deployed or evaluated ina large number of government (e.g., welfare disbursement, national ID card, issuing of driver’slicense) and civilian (e.g., computer network logon, automatic teller machine, cellular phone,Web access, smartcard) applications.