Biometrics is the use of physiological and/or behavioral characteristics to recognize or verify the identity of individuals through automated means.

It is divided as:
Physiological biometrics is based on data derived from direct measurements of parts of the human body. Fingerprints, iris scans, retina scans, hand geometry, and facial recognition are all leading physiological biometrics.

Behavioral characteristics are based on a person’s actions. Behavioral biometrics, in turn, are based on measurements and data derived from an action, thus indirectly measuring characteristics of the human body. Voice recognition, keystroke scans, and signature/sign scans are leading behavioral biometric technologies. One of the defining characteristics of a behavioral biometric is the incorporation of time as a metric, i.e., the measured behavior has a beginning, middle, and an end.

A brief introduction of the commonly used biometrics is given below:

• Deoxyribo Nucleic Acid (DNA) is the one- dimensional ultimate unique code for one’s individuality – except for the fact that identical twins have identical DNA patterns. It is, however, currently used mostly in the context of forensic applications for person recognition.

• It has been suggested that the shape of the ear and the structure of the cartilegenous tissue of the pinna are distinctive. The ear recognition approaches are based on matching the distance of salient points on the pinna from a landmark location on the ear.

• Different technologies can be used for face recognition. One approach consists on capturing an image of the face using an inexpensive camera (visible spectrum). This method typically models key features from the central portion of a facial image extracting these features from the captured image(s) that do not change over time while avoiding superficial features such as facial expressions or hair.

• Gait is the peculiar way one walks and is a complex spatio-temporal biometric.

• Hand geometry can frequently be found in physical access control for commercial and residential applications, for time and attendance systems, and for general personal authentication applications.

• Retinal Scanning method of personal authentication uses the vascular patterns of the retina of the eye.

• The way a person signs her name is known to be a characteristic of that individual. Signatures of some people vary substantially: even successive impressions of their signature are significantly different. It is based on measuring dynamic signature features such as speed, pressure and angle used when a person signs a standard, recorded pattern.

• Voice recognition or speaker recognition is the problem of identifying a speaker from a short utterance. This biometric technology uses the acoustic features of speech that have been found to differ between individuals. These acoustic patterns reflect both anatomy (e.g., size and shape of the throat and mouth) and learned behavioral patterns (e.g., voice pitch, speaking style).