How does a transition from verification to identification affect the FAR?
In a verification a biometric feature is compared with only one reference, whereas in an identification, it is compared with N (N>1) different references. This transition to an identification results in higher FAR, and in an ideal case is as follows: FARN = 1 – (1 – FAR1)N where FARN is the false acceptance rate for N different stored references. The formula is restricted to the “access control” case where the correct assignment to an identity is not essential. For an N·FAR1 significantly smaller than 1, we have approximated: FARN ~ N·FAR1 Example: A data base has 100 000 different references. In an identification, FAR is raised from 10-7 to about 10-2! If in an application the correct assignment of ID data is essential (e.g., for bank transactions), other methods have to be used, as explained under Determination of FIR.
