"Biometrics" means "life measurement" but the term is usually associated
with the use of unique physiological characteristics to identify an
individual. The application which most people associate with biometrics is
security. However, biometrics identification has eventually a much broader
relevance as computer interface becomes more natural. Knowing the person
with whom you are conversing is an important part of human interaction and
one expects computers of the future to have the same capabilities.
A number of biometric traits have been developed and are used to authenticate the person's identity. The idea is to use the special characteristics of a person to identify him. By using special characteristics we mean the using the features such as face, iris, fingerprint, signature etc.
The method of identification based on biometric characteristics is preferred over traditional passwords and PIN based methods for various reasons such as: The person to be identified is required to be physically present at the time-of-identification. Identification based on biometric techniques obviates the need to remember a password or carry a token. A biometric system is essentially a pattern recognition system which makes a personal identification by determining the authenticity of a specific physiological or behavioral characteristic possessed by the user. Biometric technologies are thus defined as the "automated methods of identifying or authenticating the identity of a living person based on a physiological or behavioral characteristic".
A biometric system can be either an 'identification' system or a 'verification' (authentication) system, which are defined below.
Identification - One to Many: Biometrics can be used to determine a person's identity even without his knowledge or consent. For example, scanning a crowd with a camera and using face recognition technology, one can determine matches against a known database.
Verification - One to One: Biometrics can also be used to verify a person's identity. For example, one can grant physical access to a secure area in a building by using finger scans or can grant access to a bank account at an ATM by using retinal scan.
Biometric authentication requires to compare a registered or enrolled biometric sample (biometric template or identifier) against a newly captured biometric sample (for example, the one captured during a login). This is a three-step process (Capture, Process, Enroll) followed by a Verification or Identification process.
During Capture process, raw biometric is captured by a sensing device such as a fingerprint scanner or video camera. The second phase of processing is to extract the distinguishing characteristics from the raw biometric sample and convert into a processed biometric identifier record (sometimes called biometric sample or biometric template). Next phase does the process of enrollment. Here the processed sample (a mathematical representation of the biometric - not the original biometric sample) is stored / registered in a storage medium for future comparison during an authentication. In many commercial applications, there is a need to store the processed biometric sample only. The original biometric sample cannot be reconstructed from this identifier.
A number of biometric characteristics may be captured in the first phase of processing. However, automated capturing and automated comparison with previously stored data requires that the biometric characteristics satisfy the following characteristics:
Among the various biometric technologies being considered, the attributes which satisfy the above requirements are fingerprint, facial features, hand geometry, voice, iris, retina, vein patterns, palm print, DNA, keystroke dynamics, ear shape, odor, signature etc.
A biometric system can be classified into two modules- (i) Database Preparation Module and (ii) Verification Module. The Database Preparation Module consists of two sub-modules, and they are (a) Enroll Module and (b) Training Module while the other module, Verification module can be divided into two modules (a) Matching Module and (b) Decision Module.
Multimodal Biometric Systems
Multimodal biometric systems are those that utilize more than one physiological or behavioral characteristic for enrollment, verification, or identification. In applications such as border entry/exit, access control, civil identification, and network security, multi-modal biometric systems are looked to as a means of
A multimodal biometric verification system can be considered as a classical information fusion problem i.e. can be thought to combine evidence provided by different biometrics to improve the overall decision accuracy. Generally, multiple evidences can be integrated at one of the following three levels.