A biometric technique that uses characteristics of a person’s signature (including pressure, pen lifts, speed and direction of pen strokes) to authenticate identity. Signature is less accurate than some other biometrics (e.g., fingerprints, iris) but is popular in document authentication applications that have traditionally used written signatures. Some growth may be fueled by the adoption of pen-based devices (e.g., the PalmPilot) that can double as a signature input tablet.