It's like a tiny Microsoft Kinect embedded in your phone, plus machine learning.
By now, you've probably heard: The upcoming iPhone X doesn't have a home button, and it doesn't have a fingerprint sensor either.
How will you log into your phone? How will you tap-to-pay? Apple's hoping you'll use the brand-new Face ID -- where you simply look at your phone to be logged in automatically.
I know what you're thinking: Can you trust a facial scanner? Could someone fool it with a picture of your face? And what will Apple do with the scans afterwards? In the wake of news that Samsung's rival Face Unlock feature isn't particularly secure, you might be wondering whether face unlocks are really a great idea.
But in the days since Apple's announcement, journalists have collected the answers to most of your burning questions. Here's how Face ID works -- and how Apple plans to secure your data.
The first thing you need to understand about face recognition is that it has generally sucked. Typically, phonemakers simply use the existing selfie cam on your phone -- which can only take flat pictures of your face. (That's why you can fool a Samsung Galaxy Note 8 with a similarly flat photo.)
But last Tuesday, Apple introduced the iPhone X's TrueDepth sensor, which crams a ton of hardware into a pretty tiny space -- the typical front-facing camera, microphone, speaker, ambient light and proximity sensors are now joined by a new infrared camera, dot projector and flood illuminator.
In other words: It can see in 3D.
While those sensors sound awfully complicated, the process appears to be pretty simple: The phone lights up your face, fires out 30,000 invisible infrared dots that highlight your features and create a rough pattern, takes pictures of those dots with the infrared camera and then decides whether the picture looks like you.
Apple says the chance of fooling Face ID is literally 1 in a million -- compared with 1 in 50,000 that a random person could fool the fingerprint unlock on an older iPhone.
(Want to know way more? Here are 10 things we learned about the tech from Apple's new whitepaper.)
If the tech sounds familiar, you might have used a similar technology before: Microsoft's Kinect, for the Xbox 360 and Xbox One, allowed you to control games by watching the pattern of infrared dots that it projected across your living room.
In fact, Apple isn't the first company to let you log into a computer using the same basic idea. Microsoft's Windows Hello will let you log in to Windows 10 computers if they're equipped with a depth-sensing infrared camera setup, and can allegedly even tell twins apart. I've reviewed a few laptops with the feature, and it's pretty cool.
Still, Apple definitely seems to be breaking some new ground with Face ID -- both in terms of fitting the tech into a reasonably thin, narrow phone and by getting banks on board.
Apple says Face ID is secure enough you can use it to pay in actual brick-and-mortar stores -- something we were led to believe would take years to become a reality, after Samsung revealed its Face Unlock wasn't secure enough for payments. (Samsung requires you to use a fingerprint reader or iris scanner for that.)
Apple's tech should work with apps, too. Any that used the Touch ID fingerprint sensor -- Apple name-dropped Mint, 1Password and E-Trade -- should be able to use Face ID as well.
To make Face ID that secure, private and still speedy enough to use quickly, Apple says it never stores your face scans in the cloud, but rather on an encrypted part of your phone.
Specifically, it runs every facial scan through the Secure Enclave, a dedicated co-processor with its own encrypted memory, secure boot process and a random number generator. Apple tells TechCrunch it couldn't access that data even if it wanted to, and neither can app developers -- they only see a rough depth map like the one in the image below.
Plus, the tech is designed to only recognize you when you've got both eyes open and are looking straight at the phone.
Sure, a glance isn't particularly secure if, say, an authoritarian government asks you to unlock your phone -- but you can quickly disable Face ID by holding down the Power and Volume buttons for a few moments, according to Apple.
On a less somber note, Apple says it uses machine learning so Face ID can grow with you -- machine learning that also runs locally on the phone's processor, instead of phoning home to servers in the cloud. Apple says it's smart enough to recognize your face if you change hairstyles, add a scarf and hat or grow a beard.
Obviously, we haven't had time to test Face ID for ourselves yet, and it's not yet clear whether it'll be better than the Touch ID fingerprint sensor overall. But there's a world of possibility for the new camera if it really does work -- and if consumers don't reject it for sounding a little too creepy.
Speaking of which: Have you seen this hilarious Conan O'Brien video?
Apple Sept. 12 iPhone event live coverage: Read what happened in CNET's live blog.
iPhone X, iPhone 8: Everything we know about Apple's new iPhones.
Everything Apple just announced: Get the details.