Advances in Fingerprint Technology.pdf

Probability
Impostor Distribution
FRR
Genuine Distribution
Score Threshold Score, T
Figure 8.23 Probability distributions of matcher scores from genuine mated and
impostor fingerprint pairs. FRR and FAR denote the false reject and false accept
error rates, respectively.
sample set. Finally, the system may have to be tuned to peculiarities of the
sample data (without overtuning it to arrive at optimistic error rate estimates).
Techniques such as data sequestering 63 may be necessary to avoid
overtuning the system.
In principle, one can use the false (impostor) acceptance rate (FAR), the
false (genuine individual) reject rate (FRR) at a single operating point, and
the equal error rate (EER)* to indicate the identification accuracy of a biometric
system. 64,65 In practice, these performance metrics can only be estimated
from empirical data and the estimates of the performance are
dependent on the fingerprint database used in the experiments. Therefore,
they are meaningful only for a specific database in a specific test environment.
For example, the performance of a biometric system as claimed by its manufacturer
had an FRR of 0.3% and an FAR of 0.1%. An independent test by
the Sandia National Laboratory found that the same system had an FRR of
25% with an unknown FAR. 66 To provide a more reliable assessment of a
biometric system, some more descriptive measures of performance are necessary.
Receiver operating characteristic curve (ROC) is one such descriptive
measure of performance (see Figure 8.21).
* Equal error rate is defined as the error rate value where FAR and FRR are equal.
FAR