Biometric Identification Technologies
Abstract: When it comes to working biometric identification technologies, it's not only our fingerprints that do the talking. Now, our eyes, hands, signature, speech, and even facial temperature can ID us.
A biometric system is essentially a pattern recognition system that makes a personal identification by establishing the authenticity of a specific physiological or behavioural characteristic possessed by the user. During the enrolment phase, the biometric characteristic of an individual is first scanned by a biometric sensor to acquire a digital representation of the characteristic. In order to facilitate matching and to reduce the storage requirements, the digital representation is further processed by a feature extractor to generate a compact but expressive representation, called a "template." Depending on the application, the template may be stored in the central database of the biometric system or be recorded on a magnetic card or smartcard issued to the individual. During the recognition phase, the biometric reader captures the characteristic of the individual to be identified and converts it to a digital format, which is further processed by the feature extractor to produce the same representation as the template. The resulting representation is fed to the feature matcher that compares it against the template(s) to establish the identity of the individual. An ideal biometric should be universal, where each person possesses the characteristic; unique, where no two persons should share the characteristic; permanent, where the characteristic should neither change nor be alterable; and collectable, where the characteristic is readily presentable to a sensor and is easily quantifiable. In practice, however, a characteristic that satisfies all these requirements may not always be feasible for a useful biometric system.
The designer of a practical biometric system must also consider a number of other issues, including:
- Performance, that is, a system's accuracy, speed, robustness, as well as its resource requirements, and operational or environmental factors that affect its accuracy and speed; • Acceptability, or the extent people are willing to accept for a particular biometric identifier in their daily lives;
- Circumvention, as in how easy it is to fool the system through fraudulent methods. Depending on the application context, a biometric system may either operate in a verification (authentication) mode or in a recognition (identification) mode . A verification system authenticates a person's identity by comparing the captured biometric characteristic with the person's own biometric template(s) restored in the database. In this system, an individual who desires to be identified submits a claim to an identity usually via a magnetic-stripe card, login name, or smartcard, and the system either rejects or accepts the submitted claim of identity. In a recognition system, the system establishes a subject's identity (or fails to if the subject is not enrolled in the system database) by searching the entire template database for a match--without the subject having to claim an identity.
Biometrics is a rapidly evolving technology that has been widely used in forensics, such as criminal identification and prison security. Biometric identifications also under serious consideration for adoption in a broad range of civilian applications. E-commerce and e-banking are two of the most important application areas due to the rapid progress in electronic transactions. These applications include electronic fund transfers, ATM security, check cashing, credit card security, smartcards security, and online transactions. There are currently several large biometric security projects in these areas under development, including credit card security (MasterCard) and smartcard security (IBM and American Express). A variety of biometric technologies are now competing to demonstrate their efficacy in these areas. The market of physical access control is currently dominated by token-based technology. However, it is predicted that, with the progress in biometric technology, market share will increasingly shift to biometric techniques. Information system and computer-network security, such as user authentication and access to databases via remote login is another potential application area. It is expected that more and more information systems and computer-networks will be secured with biometrics with the rapid expansion of Internet and intranet. With the introduction of biometrics, government benefits distribution programs such as welfare disbursements will experience substantial savings in deterring multiple claimants. In addition, customs and immigration initiatives such as INS Passenger Accelerated Service System (INSPASS), which permits faster processing of passengers at immigration checkpoints based on hand geometry, will greatly increase the operational efficiency. A biometric-based national identification system provides a unique ID to the citizens and integrates different government services. Biometrics based voter registration prevents voter fraud; and biometrics-based driver registration enforces issuing only a single driver license to a person; and biometrics- based time/attendance monitoring systems prevent abuses of the current token-based manual systems.
There are a multitude of biometric techniques either widely used or under investigation. These include, facial imaging (both optical and infrared), hand and finger geometry, eye-based methods (iris and retina), signature, voice, vein geometry, keystroke, and finger- and palm-print imaging.
Face. Facial images are probably the most common biometric characteristic used by humans to make a personal identification. Identification based on face is one of the most active areas of research, with applications ranging from the static, controlled mug-shot verification to dynamic, uncontrolled face identification in a cluttered background . Approaches to face recognition are typically based on location and shape of facial attributes, such as the eyes, eyebrows, nose, lips, and chin shape and their spatial relationships; the overall (global) analysis of the face image and its break-down into a number of canonical faces, or a combination thereof. While performance of the systems  commercially available is reasonable, it is questionable whether the face itself, without any contextual information, is a sufficient basis for recognizing a person from a large number of identities with an extremely high level of confidence. It is difficult to recognize a face from images captured from two drastically different views. Further, current face recognition systems impose a number of restrictions on how the facial images are obtained, sometimes requiring a simple background or special illumination. In order for the face recognition systems to be widely adopted, they should automatically detect whether a face is present in the acquired image; locate the face if there is one; and recognize the face from a general viewpoint.
Fingerprints. Humans have used fingerprints for personal identification for centuries and the validity of fingerprint identification has been well-established . A fingerprint is the pattern of ridges and furrows on the surface of a fingertip, the formation of which is determined during the fatal period. They are so distinct that even fingerprints of identical twins are different as are the prints on each finger of the same person. With the development of solid-state sensors, the marginal cost of incorporating a fingerprint-based biometric system may soon become affordable in many applications. Consequently, fingerprints are expected to lead the biometric applications in the near future, with multiple fingerprints providing sufficient information to allow for large-scale recognition involving millions of identities. One problem with fingerprint technology is its lack of acceptability by a typical user, because fingerprints have traditionally been associated with criminal investigations and police work. Another problem is that automatic fingerprint identification generally requires a large amount of computational resources. Finally, fingerprints of a small fraction of a population may be unsuitable for automatic identification because of genetic, aging, environmental, or occupational reasons.
Hand geometry. A variety of measurements of the human hand, including its shape, and lengths and widths of the fingers, can be used as biometric characteristics . Hand geometry-based biometric systems have been installed at hundreds of locations around the world. The technique is very simple, relatively easy to use, and inexpensive. Operational environmental factors such as dry weather, or individual anomalies such as dry skin, generally have no negative effects on identification accuracy. A main disadvantage of this technique is its low discriminative capability. Hand geometry information may not be invariant over the lifespan of an individual, especially during childhood. In addition, an individual's jewellery or limitations in dexterity (for example, from arthritis), may pose further challenges in extracting the correct hand geometry information. Lastly, because the physical size of a hand geometry-based system is large, it cannot be used in certain applications such as laptop computers.
Retinal Pattern. The pattern formed by veins beneath the retinal surface in an eye is stable and unique  and is, therefore, an accurate and feasible characteristic for recognition. Digital images of retinal patterns can be acquired by projecting a low intensity beam of visual or infrared light into the eye and capturing an image of the retina using optics similar to a retina scope. In order to acquire a fixed portion of the retinal vasculature needed for identification, the subject is required to closely gaze into an eye-piece and focus on a predetermined spot in the visual field. In many applications, the degree of user cooperation required in imaging a retina may not be acceptable to the subjects undergoing identification. Another disadvantage of this biometrics is that retinal scanners are expensive. A number of retinal scan based biometric systems have been installed in several highly secure environments such as prisons.
Iris. The iris is the annular region of the eye bounded by the pupil and the sclera (white of the eye) on either side. The visual texture of the iris stabilizes during the first two years of life and its complex structure carries very distinctive information useful for identification of individuals. Initial available results on accuracy and speed of iris-based identification are promising and point to the feasibility of a large-scale recognition using iris information. Each iris is unique and even irises of identical twins are different. Furthermore, the iris is more readily imaged than retina; it is extremely difficult to surgically tamper iris texture information and it is easy to detect artificial irises (for example, designer contact lenses) . Although the early iris-based identification systems required considerable user participation and were expensive, efforts are underway to build more user-friendly and cost-effective versions. It remains to be seen how this relatively recently discovered biometric matures and gains public acceptance.
Signature. Each person has a unique style of handwriting. However, no two signatures of a person are exactly identical; the variations from a typical signature also depend upon the physical and emotional state of a person. The identification accuracy of systems based on this highly behavioural biometric is reasonable but does not appear to be sufficiently high to lead to large-scale recognition. There are two approaches to identification based on signature : static and dynamic. Static signature identification uses only the geometric (shape) features of a signature, whereas dynamic (online) signature identification uses both the geometric (shape) features and the dynamic features such as acceleration, velocity, pressure, and trajectory profiles of the signature. An inherent advantage of a signature-based biometric system is that the signature has been established as an acceptable form of personal identification method and can be incorporated transparently into the existing business processes requiring signatures such as credit card transactions. biometric technologies based on perceptions of three biometrics experts.
Speech. Speech is a predominantly behavioural biometrics. The invariance in the individual characteristics of human speech is primarily due to relatively invariant shape/size of the appendages (vocal tracts, mouth, nasal cavities, lips) synthesizing the sound . Speech of a person is distinctive but may not contain sufficient invariant information to offer large-scale recognition. Speech-based verification could be based on either a text-dependent or a text-independent speech input. A text dependent verification authenticates the identity of an individual based on the utterance of a fixed predetermined phrase. A text-independent verification verifies the identity of a speaker independent of the phrase, which is more difficult than a text-dependent verification but offers more protection against fraud. Generally, people are willing to accept a speech-based biometric system. However, speech-based features are sensitive to a number of factors such as background noise as well as the emotional and physical state of the speaker. Speech-based authentication is currently restricted to low-security applications because of high variability in an individual's voice and poor accuracy performance of a typical speech-based authentication system.
Biometrics refers to automatic identification of a person based on his or her physiological or behavioural characteristics. It provides a better solution for the increased security requirements of our information society than traditional identification methods such as passwords and PINs. As biometric sensors become less expensive and miniaturized, and as the public realizes that biometrics is actually an effective strategy for protection of privacy and from fraud, this technology is likely to be used in almost every transaction needing authentication of personal identity.
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