A biometric system can be regarded as a pattern recognition system. In this chapter, we discuss two advanced pattern recognition technologies for biometric recognition, biometric data discrimination and multi-biometrics, to enhance the recognition performance of biometric systems. In Section 1.1, we discuss the necessity, importance, and applications of biometric recognition technology. A brief introduction of main biometric recognition technologies are presented in Section 1.2. In Section 1.3, we describe two advanced biometric recognition technologies, biometric data discrimination and multi-biometric technologies. Section 1.4 outlines the history of related work and highlights the content of each chapter of this book.
Reliable personal recognition techniques play a critical role in our everyday and social activities. In access control, authorized users should be allowed for entrance with high accuracy while unauthorized users should be denied. In welfare benefit disbursement, people not only should verify whether the identity of a person is whom he/she claimed to be, but also should avoid the occurrence that one person claims to be another person to receive the welfare benefit twice (double dipping).
Traditionally, there are two categories of personal recognition approaches, token-based and knowledge-based (Miller, 1994). In the token-based approach, the identity of a person is verified according to what he/she has. Anyone possessed a certain physical object (token), e.g., keys or ID cards, is authorized to receive the associated service. The knowledge-based approaches authenticate the identity of an individual according to what he/she knows. Any individuals with certain secret knowledge, such as passwords and answers to questions, would receive the associated service. Both the token-based and the knowledge-based approaches, however, have some inherent limitations. In the token-based approach, the “token” could be stolen or lost. In the knowledge-based approach, the “secret knowledge” could be guessed, forgotten, or shared.
Biometric recognition is an emerging personal recognition technology developed to overcome the inherent limitations of the traditional personal recognition approaches (Jain, Bolle, & Pankanti, 1999a; Zhang, 2000, 2002, & 2004; Wayman, 2005; Bolle, 2004). The term biometrics, which comes from the Greek words bios (life) and metrikos (measure), refers to a number of technologies to authenticate persons using their physical traits such as fingerprints, iris, retina, speech, face and palm print or behavior traits such as gait, handwritten signature and keystrokes. In other words, biometric recognition recognizes the identity of an individual according to who he/she is. Compared with the token-based and the knowledge-based methods, biometric identifiers cannot be easily forged, shared, forgotten, or lost, and thus can provide better security, higher efficiency, and increased user convenience.
Biometric recognition lays the foundation for an extensive array of highly secure authentication and reliable personal verification (or identification) solutions. The first commercial biometric system, Identimat, was developed in 1970s, as part of an employee time clock at Shearson Hamill, a Wall Street investment firm (Miller, 1994). It measured the shape of the hand and the lengths of the fingers. At the same time, fingerprint-based automatic personal authentication systems were widely used in law enforcement by the FBI and by US government departments. Subsequently, advances in hardware such as faster processing power and greater memory capacity made biometrics more feasible and effective. Since the 1990s, iris, retina, face, voice, palm print, signature and DNA technologies have joined the biometric family (Jain et al., 1999a; Zhang, 2000).
With the increasing demand for reliable and automatic solutions to security systems, biometric recognition is becoming ever more widely deployed in many commercial, government, and forensic applications. After the 911 terrorist attacks, the interest in biometrics-based security solutions and applications increased dramatically, especially in the need to identify individuals in crowds. Some airlines have implemented iris recognition technology in airplane control rooms to prevent any entry by unauthorized persons. In 2004, all Australian international airports implemented passports using face recognition technology for airline crews and this will eventually became available to all Australian passport holders (Jain et al., 1999a). Several governments are now using or will soon be using biometric recognition technology. The U.S. INSPASS immigration card and the Hong Kong ID card, for example, both store biometric features for reliable and convenient personal authentication.