U3.5 Biometric Errors

U3.5 Biometric Errors

1. FMR and the FNMR are inversely related

   • High tolerance threshold, lower imposter break in but higher denial of user access
   • Lower threshold, increases imposter break in
   • Setting the tolerance threshold involves a trade off between the 2 types of error

2. False Match Rate (FMR)

   • Probability that a biometric measurement will be incorrectly considered a match for a different individuals biometric sample
   • A function of the tolerance threshold
     • Increase the tolerance threshold, lower the FMR
     • Reduce the threshold increases the FMR
   • FMR is the probability of a false match for a single comparison

3. False Acceptance Rate FAR is the probability an imposter is accepted by the system

   • FAR is likely to be larger than the FMR
     • An imposter can try impersonate several users increasing their chances of a break in

4. False Non Match Rate FNMR

   • probability that a valid user's biometric sample will incorrectly be considered a non-match for his/her reference template.
   • Denial of access
   • Also a function of the tolerance threshold
     • Increase the tolerance threshold, the higher the FNMR
     • if the minimum degree of similarity necessary for a match is set high, a valid user may have difficulties providing a sample of his biometric data that matches closely against his own reference template.
     • if the tolerance threshold is reduced, the FNMR also decreases.
   • probability of a false non-match for a single comparison

5. False Rejection Rate

   • the probability that a valid user is rejected by the system
   • false rejection rate is typically lower than the false non-match rate

6. Equal Error Rate ERR

   • Rate at which both acceptance (FMR) and rejection (FNMR) errors are equal for any device.
     • used as a standard measurement for biometric systems because it's a simple way to compare accuracy

7. Failure to enrol rate (FTER)

   • users from the total population for whom the system is unable to generate repeatable templates
   • Those unable to present the required biometric feature, unable to provide sufficiently distinctive biometric data, those unable to match reliably against their template following an enrolment attempt
   • Will necessitate use of alternative authentication/identification
   • Lowering the quality requirements for enrolment will decrease the failure-to-enrol rate but may compromise the overall securit
   • Related to false match
   • Higher the tolerance threshold, the higher the FTER

8. Failure to Capture Rate

   • probability that the sensor system will fail to detect or correctly scan a biometric characteristic that has been presented correctly.
     • sensors designed to work on a moving target at a distance area more difficult challenge.