The Simple Math of Biometrics

To calculate the EER using the FRR/FAR crossover, the following is done: For any given threshold value from 0 to 1, respective FAR and FRR are calculated and plotted on the same graph. Since the granularity used for the values between 0 and 1 can be selected, this introduces the possibility of manipulating the results.

Measure Is Most Important

When looking at biometric systems, it is easy to get lost in all the statistical measures available. To decide what measure is most important to your choice of a biometric system, its use needs to be defined as follows:

v  Define the user population.

v  Is the application for verification or identification?

v  Are other means of authentication available?

v  What is the importance of the biometric authentication?

v  Is it driven by convenience and ease of use?

Statistical measures of biometrics can be used to decide which biometric system will best suit your needs. Not knowing the math behind a measurement should not impact one's ability to understand and compare the different statistical measures. The most important biometric statistical measures are:

v  FAR— Measures the probability that an imposter will authenticate as a legitimate user.

v  FRR— Measures the probability that a user who makes a legitimate claim about his/her identity will be falsely rejected.

v  FTE— Measures the probability that an enrollment candidate will be unable to enroll in the biometric system.

v  ERR— Measures the intrinsic strength of the biometric system and compares the strength of different biometric systems based on their EERs.