Biometrics refers to the automatic identification of a person based on his/her physiological or behavioral characteristics. This method of identification offers several advantages over traditional methods involving ID cards (tokens) or PIN numbers (passwords) for various reasons: (i) the person to be identified is required to be physically present at the point-of-identification; (ii) identification based on biometric techniques obviates the need to remember a password or carry a token. With the increased integration of computers and Internet into our everyday lives, it is necessary to protect sensitive and personal data. By replacing PINs (or using biometrics in addition to PINs), biometric techniques can potentially prevent unauthorized access to ATMs, cellular phones, laptops, and computer networks. Unlike biometric traits, PINs or passwords may be forgotten, and tokens like passports and driver's licenses may be forged, stolen, or lost. Thus, biometric systems are being deployed to enhance security and reduce financial fraud. Various biometric traits are being used for real-time recognition, the most popular being face, iris and fingerprint. However, there are biometric systems that are based on retinal scan, voice, signature and hand geometry.

A biometric system is essentially a pattern recognition system which recognizes a user by determining the authenticity of a specific physiological or behavioral characteristic possessed by the user. Several important issues must be considered in designing a practical biometric system. First, a user must be enrolled in the system so that his biometric template can be captured. This template is securely stored in a central database or a smart card issued to the user. The template is retrieved when an individual needs to be identified. Depending on the context, a biometric system can operate either in a verification (authentication) or an identification mode.

Verification vs. Identification:

There are two different ways to recognize a person: verification and identification. Verification (Am I who I claim I am?) involves confirming or denying a person's claimed identity. On the other hand, in identification, the system has to recognize a person (Who am I? ) from a list of N users in the template database. Identification is a more challenging problem because it involves 1:N matching compared to 1:1 matching for verification.

Applications:

While biometric systems, particularly automatic fingerprint identification systems (AFIS), has been widely used in forensics for criminal identification, recent advancements in biometric sensors and matching algorithms have led to the deployment of biometric authentication in a large number of civilian and government applications. Biometrics is being used for physical access control, computer log-in, welfare disbursement, international border crossing and national ID cards. It can be used to verify a customer during transactions conducted via telephone and Internet (electronic commerce and electronic banking). In automobiles, biometrics is be adopted to replace keys for keyless entry and keyless ignition. Due to increased security threats, the ICAO (International Civil Aviation Organization) has approved the use of e-passports (passports with an embedded chip containing the holder's facial image and other traits).