Biometric Authentication

The FTE is defined as the probability that a user attempting to bio metrically enroll will be unable to. For example, Craig goes to the group in his company responsible for biometric enrollments. He is quickly instructed on the use of a biometric device, and then he attempts to have his biometric trait enrolled. At this time, he is unable to be enrolled. What defines his FTE can influence this measure. If the FTE is defined as a single-attempt failure, then the FTE will likely be higher than what would be seen over a larger group of people.

The FTE is normally defined by a minimum of three attempts. This is justified by the Rule of Three. The Rule of Three in this case provides us with a confidence level for a given error rate for our FTE. It also assumes that each attempt to enroll is independent, identically distributed, and that the user population size is significantly large enough. For example, if Craig is part of a population of 300 people, then using the Rule of Three for a 95% confidence level, we would obtain an FTE of 1%. Thus, if Craig is still unable to be enrolled after three attempts, he has had an FTE.

The EER is defined as the crossover point on a graph that has both the FAR and FRR curves plotted. The EER can also be calculated from a receiver operating characteristic (ROC) curve, which plots FAR against FRR to determine a particular device's sensitivity and accuracy. The choice of using the crossover point of the FRR/FAR or using a ROC is a question of significance. An EER calculated using the FRR and FAR is susceptible to manipulation based on the granularity of threshold values. A ROC-based EER is not affected by such manipulations because the FRR and FAR are graphed together. Thus, the EER calculated using a ROC is less dependent on scaling.