We know quite a lot about the iPhone 5s's fingerprint scanner, Touch ID. The advanced sensor works seamlessly and learns more about your prints over time so it continues to expand your fingerprint map as additional overlapping nodes are identified with each use.
It can match prints in any orientation, unless your fingers are greasy or wet, or there's some dirt or debris on the Home button. There's a 1 in 50,000 chance of a successful random match with someone else’s print, which is much better than the 1 in 10,000 odds of guessing a typical four-digit passcode.
The Touch ID sensor doesn't store actual fingerprint images and instead creates an encrypted profile of your print and stores it on a module on the A7 processor called the Secure Enclave that's walled off from the rest of the system.
After five unsuccessful fingerprint match attempts, or after every restart, the system asks for your passcode so that hackers can’t stall for time. These are pretty much key pieces of information on Touch ID that was made public since its inception.
Today, Apple updated its iOS Security white paper [PDF download] with a few previously unknown specifics relating to how Touch ID works side by side with the A7 chip and its Secure Enclave portion to detect a fingerprint match in a highly secure manner. The document also details other security safeguards Apple put in place to prevent tampering with fingerprint data...
