One of the most exciting new features on the iPhone 5s is the fingerprint sensor embedded in the device’s home button. Apple calls it Touch ID, and as it gains more uses in the OS, it could have a huge impact on your mobile experience.

For now, Touch ID is limited to making purchases in iTunes or the App Store, letting you buy things like movies, music, and apps with a press of your finger instead of an Apple ID. And of course, you can also use your fingerprint to unlock your iPhone too.

Here’s what you need to know.

Setting It Up

Getting Touch ID up and running is pretty straightforward. First, go to Settings > Passcode & Fingerprint > Fingerprint and then choose “Add a Fingerprint.” Then just follow the onscreen prompts to get every angle and intricacy of your fingerprint documented by the scanner. If more than one person will be sharing the device, or you want to be able to use different fingers with Touch ID, you can set up and name multiple fingerprint accounts.

Using Touch ID

Touch ID can only be used to unlock your iPhone 5s and make App Store or iTunes purchases — at least for now. Just place your finger on the home button for a second or two, and like magic, you’ve been verified. Touch ID has 360-degree fingerprint readability. Theoretically, that means no matter how you place your finger on the home button’s sensor, it should be able to read your print. Touch ID evenworks on toes and (to an extent) with a cat’s paw, should you want to impress non-techy friends with a silly party trick.
At this time, Touch ID isn’t available for third-party apps to tap into. If it requires a password, you’ll still have to enter it manually.

How Secure Is It?

One of the big questions when Apple first introduced Touch ID was how our fingerprint information would be stored. Would it be accessible to any app that wants to use it? Is your fingerprint scan going straight to PRISM and the NSA’s servers?
Apple stores your fingerprint information directly on the A7 processor, in what’
s called the Secure Enclave. The information isn’t accessible to any software, servers, or to iCloud. How this likely works on the A7 processor is discussed in detail on Quora, but basically, the hardware and software portions of the device are partitioned into “regular” and “secure” areas. Regular components are unable to access data or activities that occur in the secure areas. To get at data stored in the secure area, it would require “a rather large magnitude of hardware hacking,” Brian Roemmele writes.
Don’t assume people aren’t going to try their darndest to hack Touch ID though. Some have already offered rewards to anyone who’s able to break into Apple’s new fingerprint sensing technology (the bounties range from “a bottle of Patron Silver” to a whopping $10,000 from IO Capital).