Full Apple chiefs interview transcript is out: iPhone is just an elegant, indispensable tool

Well, I mean, just to the broad point that you decide you want to do something like, “wouldn’t it be great if you could use your finger to unlock your phone or to make a purchase?” It sounds like a simple idea. But how many places could that become a bad idea because you failed to execute on it? We thought, “Well, one place where that could be a bad idea is somebody who writes a malicious app, somebody who breaks into your phone, starts capturing your fingerprint. What are they doing with that? Can they reuse that in some other location? Can they use it to spoof their way into other people’s phones?”

Well, that would be worse than never having done the feature at all if you did those things, right? And so you take that all the way to that spectrum, and we said, “My gosh, we’re going to have to build in our silicon a little island, a little enclave that’s walled off so that literally the main processor—no matter if you took ownership of the whole device and ran whatever code you wanted on the main processor—could not get that fingerprint out of there. Literally, the physical lines of communication in and out of the chip would not permit that ever to escape. It was something we considered fundamental to solving the overall problem.