[jbg_]

A fingerprint is just a really complex password that you leave on everything you touch. Your face is just a really complex password that is written on the front of your head.

It should be self-evident that neither of these is "secure" for some level of "security", but they might be perfectly fine for the level of threat that you face, which is not likely to be particularly high. But I don't know you, so maybe you face a higher-than-average level of threat, in which case, yes, a sufficiently long password/passphrase that you memorise is probably the best option for your mobile device.

[contras1970]

fingerprints and faces are just really complex usernames: they're not secret at all.

[valuearb]

Your biometric measurements are essentially secrets. They work today because it's far too difficult for a thief to steal your device AND copy your biometrics at the same time. This makes them the most secure tokens we have in real world use, given the number of people with 0000 passcodes.

Eventually they may become easy to copy, then their utility as secrets will be gone.

[timthelion]

Advanced fingerprint recognition devices recognize things that are not left on things that you touch. They look under the skin at blood vessel and measure body capacitance and other statistics. That's why there is the weird light on the "biometrics" device in the airport, to be able to see through the outer layers of skin.

https://en.wikipedia.org/wiki/Finger_vein_recognition

[tzahola]

The solution is obvious: genital scanners! https://www.youtube.com/watch?v=0zu4XlM_89s