We use four kinds of evidence to authenticate a claim of identity, something only one person knows, e.g., pass-phrase, is, e.g., visage, fingerprint, has i.e., custody, e.g., unique keys, tokens, or can do, e.g. speech, signature dynamics. Since all of these have fundamental limitations, we use them in combination such that one compensates for the limitations of another.

While it is somewhat counter-intuitive, biometrics are no less limited than the the other three Their fundamental limitation is that they can be copied and fraudulently re-used. We use them more for convenience than security. We use them in combination with other mechanisms in systems of strong authentication.

For example, while the ability to spoof Touch ID might be useful in gaining access to,the content and capabilities of my mobile, it is far from sufficient. First one must have the phone. While there have been demonstrations of retrieving latent prints using gelatin and using them to fool biometric system, that is an easier problem than trying to go from a paper record.

Such demonstrations, in and of themselves, do not represent a risk. I am confident that no one is using such an attack against my mobile because I have custody of it. Touch ID, much like the PIN for which it may substitute, is used to resist the fraudulent use of the lost or stolen mobile only for,the short time until its loss is noticed and the phone disabled.

Note that an attacker only gets five chances to spoof Touch ID and ten to,guess the PIN. Then my mobile erases,itself.

Biometrics do not rely upon secrecy; disclosure of the reference does not compromise the system. Rather they rely upon the difficulty of counterfeiting the biometric.