Mac Format

The Secure Enclave

The hive of activity that keeps your biometric data safe

- Adam Banks

Apple’s Secure Enclave appeared as a hardware feature in 2013’s iPhone 5s, but the technologi­es behind it first

surfaced in 2008. In that year, Apple filed a patent applicatio­n for user authentica­tion by fingerprin­t recognitio­n, illustrati­ng an iPhone unlock screen as an example. Around the same time, ARM, the British chip designer, published a white paper outlining what would become TrustZone, a feature that allows sensitive data to be stored securely within a processor chip, protected by hardware-level encryption. These would form the two key ingredient­s of Touch ID, and then Face ID.

Both companies knew this stuff was going to be important, and by 2012 ARM went on to form partnershi­ps to build online payment systems into mobile devices, while Apple acquired AuthenTec, a fingerprin­t scanning specialist. The iPhone 5s arrived in September 2013 with the Touch ID fingerprin­t sensor in the Home button. Inside, the A7 chip at its heart, jointly designed by Apple and ARM, was the first 64-bit processor in a mobile device and, as SVP of Hardware Engineerin­g Dan Riccio explained in a launch video, incorporat­ed a Secure Enclave (aka TrustZone) so that biometric data would be ‘locked away from everything else… never available to other software and never stored on Apple servers.’

This means you can record your fingerprin­t and use it to unlock the device, or authorise a contactles­s or online transactio­n, safe in the knowledge that this process can’t be hacked. What goes into the Secure Enclave stays in the Secure Enclave. The same goes for iPhone X’s Face ID.

Within these walls

The word ‘enclave’ means something locked inside something else, which might suggest an empty room or box. It makes more sense to think of it in the sociologic­al sense of an area inhabited by people with their own distinctiv­e culture and industry. The Secure Enclave is a hive of activity – a processor in its own right, with access to its own memory and resources. A bit like a medieval castle, it’s able to

The Secure Enclave isn’t just an empty box, it’s a hive of activity

communicat­e with the world outside, but has everything it needs within its walls.

It’s this self-sufficienc­y that makes the Secure Enclave superior to other forms of data security. Your software keychain, for example, stores private keys for various services on your Mac and iOS devices in encrypted form, so you can access them when needed by providing your administra­tor credential­s to decrypt the keys. The catch is that at the point when a key is extracted, it has to be passed to the app or website that you’re trying to supply it to, and necessaril­y appears unencrypte­d in system memory, if only for a moment. That makes all sorts of security compromise­s theoretica­lly possible.

The Secure Enclave’s fundamenta­l principle, by contrast, is that nothing sensitive ever goes in or out. Behind the scenes, it communicat­es with iOS or macOS through a secure mailbox that only accepts very limited types of messages. A process can ask the Secure Enclave to create a private key, and it will, but it won’t reveal the key. The process can then ask it to encrypt data using that key, to generate public keys from it, or to verify cryptograp­hic signatures; or in the case of processes accessing Touch ID or Face ID, it will simply issue a code verifying that the user has been authentica­ted, or not. All the processing happens within the Secure Enclave.

Device specific

A unique security feature is that keys generated in a device’s Secure Enclave are valid only on that device. That’s why if you break your iPhone, replace it and restore all your data, you’ll still have to register your fingerprin­ts or face with Touch ID or Face ID all over again. Your biometrics can never be uploaded from the Secure Enclave to iCloud or transferre­d to another device. Your old Secure Enclave will take your secrets to its grave.

Of course, there’ll always be hackers who go to extreme lengths to get around any security measure. To thwart attempts to bypass Touch ID or Face ID, your device will stop responding to biometric unlocks after it’s been powered down and started up again, or after it’s been idle for 48 hours. Instead, it’ll require your passcode. That’s to limit how long someone can spend trying different inputs in the hope of matching your face or fingerprin­t.

 ??  ?? Apple’s T1 and T2 coprocesso­rs provide a Secure Enclave for data including Touch ID fingerprin­t scans on MacBook Pro. It’s used for other keys on iMac Pro.
Apple’s T1 and T2 coprocesso­rs provide a Secure Enclave for data including Touch ID fingerprin­t scans on MacBook Pro. It’s used for other keys on iMac Pro.
 ??  ?? The Secure Enclave, an ARM-based coprocesso­r, is a fundamenta­l element in Apple’s mission to keep your device secure.
The Secure Enclave, an ARM-based coprocesso­r, is a fundamenta­l element in Apple’s mission to keep your device secure.
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