But that wouldn’t work with TouchID sensors right? They also check for “living tissue”. And at that point the attack becomes _very_ expensive to perform
I mean, as a electronics guy I'd say it kinda depends on how that living tissue detection is being done. You can trick a lot of sensors into outputing things that don't make much sense if you know which physical properties they are looking for.
The most sophistication would probably be something like a PPG (optical reflection changes due to blood flow in certain bands). If the fake is thin enough the PPG would likely just shine through it.
Skin resistance/humidity can be easily faked as well.
It was mentioned elsewhere in the thread that a not too thick layer of gummy bear could fool it, due to light passing through it, but getting reflected back from the back. Not sure how true is it though.