Thesis - Instituto de Telecomunicações

14 CHAPTER 2. STATE OF THE ART1. Universality — Every person should have the characteristics.2. Uniqueness — No two persons should be the same in terms of the biometric characteristics.3. Permanence — The characteristics should be time invariant.4. Collectability — The characteristics must be measurable quantitatively and easy toacquire.5. Performance — The biometric technique accuracy level should be sufficiently high.6. Acceptability — The level of user acceptance of the biometric system should be high.7. Circumvention — The system should be difficult to forge.Biometric systems have been used in a broad range of applications on several fields ofour society such as [113, 148]: forensic science, financial and trade security, physical accesscheck points, information systems security, customs and immigration, national identificationcards, and driver licenses, among others.Listing the biometric techniques currently used, or under research, we have found [114]that most of them explore characteristics extracted from: face, fingerprint, hand geometry,hand veins, palm veins, iris, retinal pattern, signature, voice-print, facial thermogram, DeoxyribonucleicAcid (DNA), palm print, body odor, keystroke dynamics, fingernail bed, earshape, ECG, heart sound, EEG, and skin/dermis analysis.Not all these characteristics are currently used in commercial applications. Novel traitsor novel formats for the extraction of characteristics from already used traits are continuouslyappearing in conferences or workshops in the area. This set of biometrics can beclustered into the ones that are already in the market, the ones in continued research activityand the novel biometric proposals.A biometric technique in an verification operating mode, has some metrics that try toevaluate the performance of the technique [153]. Two types of decisions can be made bya biometric verification system: classify as a genuine individual or as an impostor. Foreach decision an error can be made: a false rejection (type 1 error) — a legitimate useris rejected by the system; or a false acceptance (type 2 error) — an impostor is accepted