biometric local authentication fingerprint index

Question

If I'm correct, you can store up to 5 finger prints in iOS. I have came across something like weak biometric, meaning the fingerprint may not necessarily be the fingerprint of a primary user, a secondary user can also set one, so we want to restrict the fingerprint indexing to a specific impression.

Is there a way to find the index or know which finger print index was used to set up biometric to login into the application?

localAuthenticationContext.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reasonString) {
       // index of the finger print
}

Answer 1

No. Every registered fingerprint is equally valid.

If a user decides to add the finger print of another user, they give them equal access to everything as long as no passcode is required.

But the majority of users register finger prints of multiple of their own fingers; depending how you grab your phone one finger print is more practical than another. I have left and right index finger and right thumb registered. If one or two of those didn't work with your app, I would be very, very, very annoyed as a user.