Open sesame: How iOS 8 will unlock Touch ID’s power

As iOS 8—and, presumably, new iPhone and iPad hardware—approaches its release day, big changes are on the horizon for Apple’s Touch ID, a technology that has been met with less enthusiasm than it deserves.

In an attempt to set the record straight, here’s a Q&A that gives you all the information you need to start appreciating just how much this technology could improve your daily life—and all with nothing more than the touch of a finger.

What is Touch ID again?

It’s a new technology, first launched with the iPhone 5s, that uses a fingerprint reader in your handset to allow iOS to unlock certain functionality when you touch the Home button; as long as you use a finger whose characteristics you’ve previously registered. Macworld contributor Rich Mogull has all the info you need on how the sensor works.

Why should I care?

According to various surveys, the vast majority of users never lock their phones with a passcode. This is not a big deal if you spend most of your time at home, but it becomes more of a problem if you’re out all day or travel often, and your handset finds itself within reach of potential criminals. Many thieves can snatch your phone and gain access to all your private data before you can realize what’s happened and disable the handset with Find My Phone.

Touch ID is a replacement for passcode that doesn’t require remembering a potentially long series of numbers and letters, and can be used without looking at your screen—which is exactly what you’d want most when you’re out and about.

What’s happening to Touch ID in iOS 8?

In iOS 7, Touch ID can only be used to unlock your iPhone and make purchases from the App Store. With the launch of the next version of its mobile operating system, Apple is extending the same functionality to third-party apps, making it possible for you to use your finger in lieu of a login and password for many other services and apps.

This is how it’s going to work: iOS allows apps to store secure data, like, say, the username and password you use to access an online service, in a special area of the operating system’s keychain, where it is protected using a very strong form of encryption and normally locked using your passcode.

Starting with iOS 8, you will be able to use Touch ID to grant an app access to the keychain, thus avoiding having to remember all sorts of different passwords, while still retaining a high degree of security.

In fact, there’s a good argument to be made that this arrangement is potentially much more secure than traditional credentials, because, since you won’t have to remember your passwords, you will be able to pick combinations of letters, numbers, and symbols as complex and abstruse as you like, making your accounts that much harder to hack.

I heard that Touch ID can be easily hacked. Is it really secure?

Allow us a slightly more nuanced answer than a simple yes or no.

If you don’t currently lock your handset with a passcode, Touch ID is infinitely more secure than not having any protection at all. Unless all you do with your iPhone is play Flappy Bird, you’re walking around with a veritable treasure trove of personal information that a thief could use to, quite literally, destroy your life.

If you do use a passcode, the answer is a little more complicated. In theory, someone could lift your fingerprint and use it to unlock your device without your finger being anywhere in the vicinity. There are also questions of whether using a biometric sensor could lead to unintended legal consequences should you ever run afoul of the authorities. We should point out, however, that the process required to lift a fingerprint is neither simple nor quick, requires specialized tools, chemicals, and a significant amount of good luck—and can only be performed by a very determined thief who has ready access to everything you touch.

And passcodes are not without their problems, either. As recent studies show, a determined criminal could use video surveillance in a public place to make pretty good guesses about your secret code—and without being anywhere physically near you—then steal your device and cause plenty of damage in a matter of minutes. Frankly, that seems easier than stealing your fingerprints.

Ultimately, in deciding whether Touch ID is right for you, you will have to balance your need for security with the convenience of not having to type in your passcode fifty times a day just so that you can check your email. In practice, we think that Apple’s biometric solution is great for the vast majority of users. If you’re worried about your spouse, friends, or colleagues going around your home or office playing Mission: Impossible with your fingerprints, you’re probably overlooking much easier ways that they have to gain access to your personal information—like, say, waiting for you to take a trip to the kitchen for a cup of coffee and installing a key logger (or just taking a quick peek at your inbox) on your unlocked computer.

But I don’t want to give Apple my fingerprints!

That’s not really a question, but we’ve heard it often enough over the last few months that we’re going to break the rules and answer it anyway.

Here’s the good news: Your fingerprints are safe.

Touch ID doesn’t actually store a picture of your fingers; instead, it computes a really large number, called a biometric hash, that can be used to identify the individual characteristics of your finger, but that cannot be used to reconstruct a visual representation of its features. Hashing is widely used throughout the computer industry and is considered very secure—in fact, if you feel so inclined, you can grab a coffee (or maybe something stronger) and spend a few hours going over some math that explains how these algorithms work.

That’s not all, however. If you’re still worried about Apple getting its corporate hands on your biometric hash, you’ll be happy to hear that it never leaves your device: The Touch ID sensor is essentially wired directly into a special area of your iPhone’s A7 CPU, called the “secure enclave,” that encrypts it using a key that is baked right into the chip at the time of manufacture. The data never leaves the enclave, and could not be read even if someone were to physically gain access to your handset and take it apart.

Now for the bad news: There is no bad news. Despite widespread skepticism in the press, Apple has put a lot of thought into making Touch ID secure and easy to use—and, unless your finger normally rests on the big red button that unleashes America’s nuclear arsenal, you should give it serious consideration as your authentication mechanism of choice.