I wonder if the tech team involved with Face ID factored the birthday paradox into their security factor. They touted a "1 in 1,000,000" chance that someone else's face unlocks one's iPhone X.

Well, with the birthday paradox, let's say there were, say, exactly 1179 people in the Steve Jobs Auditorium and they all had iPhone Xs. That's 694,431 unique pairs of people, and there would be roughly a 50% chance of two of the attendees faces unlocking the same phone.

That's not helpful for brute forcing a single phone, but it is mildly disconcerting that a security factor of only 1 in 1,000,000 is considered a "wow" factor.

Edit: Some people are asking, "But isn't that equivalent to a six digit pin?" Yes, of course. I am just opining on the marketing spiel for security not being nearly as impressive as it sounds. More boring features like the secure enclave play a much larger role in the security of the iPhone than the "1 in X" chance of a successful unlock.