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Inside the iPhone 5S Touch ID scanner: how does the iPhone fingerprint scanner work

Mark Hattersley | Sept. 13, 2013
How does the iPhone 5S fingerprint scanner work, how secure and private is Touch ID.

The marquee feature of the iPhone 5S — the one everybody is talking about — is the new Touch ID fingerprint scanner.

Following last night's iPhone 5S announcement we've had some time with the iPhone 5S, and time to explore some of its features. Apple fans also have a lot of Touch ID questions, such as 'how does Touch ID work?' and 'How secure is Apple's new fingerprint scanner?'

In the wake of the recent NSA scandal these aren't questions to be taken lightly. So we've put together this guide to using Touch ID on the iPhone 5S.

How does the iPhone 5S finger scanner work
In it's simplest form you touch your finger to the Home Button and it unlocks the phone. This replaces the current security measure of using a four-digit PIN number or password to unlock the iPhone.

From our iPhone 5S hands-on testing we've seen that it's easy to configure Touch ID, and you can store up to five different fingers.

Once Touch ID is configured, you unlock the iPhone 5S by placing a finger on the Home Button. After a few seconds the iPhone 5S will unlock. Ashleigh Allsopp, Macworld's hands-on tester said "it made us feel a bit like we were in the future".

If Touch ID does not recognise your finger it'll give up after a couple of tries and flip over to reveal the passcode. You can use this to unlock the phone instead.

How does Touch ID work?
Touch ID takes a high resolution (550PPI) picture of the sub-epidermal layers of your skin (your fingerprints) and then compares it to the fingerprint it has on file for you. In essence Apple has turned the Home Button into a very high resolution camera.

You use the sensor to unlock your iPhone, and you can also use it to authorise purchases from iTunes Store, the App Store and the Apple BookStore. Rather than enter your four digit PIN code you simply touch your finger to the Home Button instead.

The Touch ID sensor consists of a sapphire crystal lens. Apple described this as "one of the clearest and hardest materials available." This acts as the lens and home button. This is surrounded by a steel ring that detects your finger, and these are above the sensor itself.

What doesn't Touch ID do
One major thing that Touch ID doesn't currently do is unlock anything else on your iPhone. It can't access iCloud Keychain, which is a key new feature in iOS 7. This seems like rather a big oversight on Apple's part, although the restraint could be a security measure to see how Touch ID works in the live world.


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