They said in the keynote the chance a random person could unlock your phone with FaceID is 1 in a million.

Twins and siblings that look like you are not random people.

Now I'm imagining the FBI using its facial-recognition databases and tracking down people who look like the phone owner to wave an iPhone in front of their face.

I'd watch that TV show.

"Dylan and Luke are bounty-hunters of a new breed. They have to find the long-lost twins of suspects on FBI's Most Wanted list. On this episode of Face Hunters..."

But you’d have to do it without it seeing people you don’t intend to test with. You only get 5 tries. You can’t wait too long or it will hit the timeout.

Sounds like a movie plot to me (I made a guess at one if you dig through my comment history).

Can someone help me understand why @gre got down-votes here? I don't get it.

As far as I remember, in the big reveal, they did make a point of saying that faceid had a much lower chance of of colliding than the fingerprintid system.

I'm not the down-voters, but my guess is due to citing the 1-in-a-million figure, which is Apple's claim about a random false positive, in response to a question about false positives with twins. Someone reading fast or simply not thinking critically could come away with the wrong impression.

He got downvoted because he said something that didn't match up with what OP said. In the presentation, Apple said

> The probability of a false match is different for twins and siblings that look like you

So that means the 1 in a 1,000,000 chance doesn't make sense here because Apple said the probability is different in regards to twins and siblings that look like you. So @gre just spouted off the statistic when OP was asking what the probability might be in regards to twins and siblings, because Apple says that it is different.

They did, but the quote above was about confusion between twins or siblings. Those are explicitly not random people.

For random faces, yes, but for a twin or sibling it’s more likely; what’s interesting is that they haven’t said how much more likely. If it were less than 1/50k then you might have expected them to confirm that it was still more secure than Touch ID, though that’s not certain.