Biometrics (or biometric authentication) consists of methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits. In computer science, in particular, biometrics is used as a form of identity access management and access control. It is also used to identify individuals in groups that are under surveillance.
Biometric identifiers are the distinctive, measurable characteristics used to identify individuals. The two categories of biometric identifiers include physiological and behavioral characteristics. Physiological characteristics are related to the shape of the body, and include but are not limited to: fingerprint, face recognition, DNA, palm print, hand geometry, iris recognition (which has largely replaced retina), and odour/scent. Behavioral characteristics are related to the behavior of a person, including but not limited to: typing rhythm, gait, and voice. Some researchers have coined the term behaviometrics to describe the latter class of biometrics.
More traditional means of access control include token-based identification systems, such as a driver's license or passport, and knowledge-based identification systems, such as a password or personal identification number. Since biometric identifiers are unique to individuals, they are more reliable in verifying identity than token and knowledge-based methods, however, the collection of biometric identifiers raises privacy concerns about the ultimate use of this information.