The term biometrics applies to a broad range of electronic techniques that employ the physical characteristics of human beings as a means of authentication. In a sense, human beings already routinely authenticate one another biometrically: confirming the identity of a friend on the telephone by the sound of his or her voice is a simple instance of this. A number of biometric techniques have been proposed for use with computer systems. These include (among a wide variety of others) fingerprint readers, iris scanners, face imaging devices, hand geometry readers, and voice readers. Usage of biometric authentication techniques is often recommended in conjunction with other user authentication methods, rather than as a single, exclusive method.
Fingerprint readers are likely to become a common form of biometric authentication device in the coming years. To identify herself to a server using a fingerprint reader, a user places her finger on a small reading device. This device measures various characteristics of the patterns associated with the fingerprint of the user, and typically transmits these measurements to a server. The server compares the measurements taken by the reader against a registered set of measurements for the user. The server authenticates the user only if the two sets of measurements correspond closely to one another. One significant characteristic of this and other biometric technologies is that matching must generally be determined on an approximate basis, with parameters tuned appropriately to make the occurrence of false positive matches or false negative rejections acceptably infrequent.