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A type II error represents a false positive, implying that an impostor or innocent
bystander is identified as the correct subject. The false acceptance rate (FAR)
stands for the rate at which the algorithm accepts an incorrect subject as true.
Another classification error is the false rejection rate (FRR), which stands for the
rate at which the algorithm incorrectly discards or rejects a matching subject. The
crossover error rate (CER) compares the FAR to the FRR and provides the statistical point where the false rejection rate equals the FAR. Each one of these error
types can be measured based on different statistical modeling, which is beyond the
scope of this chapter.
Having discussed the general biometrics methodologies, next we discuss the specific types of bioinformatics identification.
18.9.2 BIOMETRICS USING FINGERPRINTS
The use of fingerprints for recognition purposes dates back to the late eighteen hundreds. It is widely assumed that fingerprint of a person does not change over time
and therefore is a unique identifier of its owner. The hypothesis that fingerprints are
unique has so far not been discarded; however, fingerprints do change as a result of
factors such as scars or surgical alterations.
Several reference points used in fingerprint identification are shown in
Figure 18.16. The various features that are identified in the fingerprint classification
are divided in major and minor features. The main reference points that identify the
subpatterns in the fingerprint are outlined in Figure 18.16. These are some additional
minor reference features, also shown in Figure 18.16, that are used in the complete
fingerprint analysis and recognition.
The major features are the presence of either or any of the following three
characteristics in the ridge pattern: an arch, a loop, or a whorl as illustrated in
Figure  18.16. Some of the minor features are certain ridge features such as ridge
branches (bifurcations) or ridge endings. The minor features are grouped in a category
Main features
Minutiae
Core
Crossover
Pore
Delta
Bifurcation
Ridge ending
Island
Loop
Arch
Whorl
FIGURE 18.16 Characteristic reference points used in fingerprint identification.