Passcodes suck. They take a long time to type in, it’s easy to forget them and most people probably pick something really easy to guess, which hurts their security. This is why biometric unlock methods are so popular. 

All but the most inexpensive smartphones now have fingerprint scanners built-in. One little touch and your phone unlocks, which is pretty convenient. But more devices are also now using facial recognition instead since screens are getting so large. Apple is no different and offers devices that use both of these technologies to secure them. Technologies that are officially known as Face ID and Touch ID.

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    Someone using Face ID with an iPhone

    But how do Face ID and fingerprint scans work?

    What Are Face ID & Touch ID?

    The obvious answer to this question is that Face ID is a face unlock system and Touch ID is a fingerprint unlock system. Job done. End of article. Right? Well, it’s a little more complicated than that because although lots of different companies use faces and fingerprints to unlock their devices, they don’t all work in the same way.

    These two biometric systems are Apple’s proprietary solutions to the biometric problem. This matters because companies like Apple feel that their approach and technology are more secure than their competition. It matters because hackers and other security specialists have managed to fool systems like these in the past. 

    A fingerprint

    As you’d expect, there’s a race between the creators of biometric security sensors and those who want to defeat them. You must know how the sensors on your Apple device work and what their limitations are.

    How Does Face ID & Touch ID Work?

    Touch ID is Apple’s most mature biometric system and you’ll find it on certain models of iPhones, iPads, and MacBook Pros. Its sensors use the sapphire crystal as the button material. This is very hard and incredibly resistant to scratches, which is why high-end smartphone cameras also use sapphire lens covers. 

    When you place your finger on the button, a very high-resolution image is taken of your fingertip. A proprietary software algorithm then examines the image, transforming your fingerprint into pure math. This is then compared to the stored mathematical transformation of the fingerprint that was registered when Touch ID was set up. If they match, then the device unlocks.

    Machine Learning

    Face ID works in a pretty smart way as well. Many devices use a normal camera for facial recognition. It compares the photo it has on record with the one you are presenting to unlock the device. The software that does the facial matching is quite sophisticated, but many of these cameras can’t tell the difference between a photo or a mask, so they can be fooled into unlocking.

    Face ID, on the other hand, makes use of a specialized TrueDepth camera to create a very detailed depth map of your face. One with over 30 000 points. It combines this with an infrared image of your face to create a facial profile. The neural net machine learning hardware components of modern Apple mobile device processors make this level of sophistication possible.

    So how secure are these technologies and are they good enough for you to trust?

    General Biometric Security Flaws

    First of all, some security vulnerabilities apply to biometric systems in general. The biggest problem with using an aspect of your biology to unlock something is that you can’t change it. If someone managed to make a perfect copy of your fingerprint or face, they could unlock anything. If someone figures out a password or passcode, just change it. 

    Someone hiding behind a mask

    This sort of thing has happened in the past and the way that biometric sensors have got around it is by becoming more detailed and looking at multiple aspects of your biology. For example, finer details of your fingerprints or the presence of body heat. Those who want to defeat these systems have to get better at replicating your biology, which is impractical for the average hacker at a certain point.

    The biggest weakness of biometric systems is a pretty simple one. Someone can simply take your finger or face and force you to unlock your device. That’s different from a password or code which you can “forget” or otherwise withhold. We’ll deal with this scenario at the end of the article.

    How Secure Are Face ID & Touch ID?

    This is a bit of a loaded question since that depends on what your definition of ‘secure’ is. Usually, the security of systems like these is expressed as the odds of someone randomly beating them. That’s the “brute force” method of cracking a digital lock. For Touch ID there’s only a 1 in 500,000 chance of someone’s fingerprint being similar enough to yours that Touch ID will be fooled. 

    Of course, that’s very different compared to someone making an impression of your fingerprint or creating fake ones from a scan. Then again, how likely that is to happen depends on who you are and if someone would be motivated to take this extreme path. If you’re a VIP who draws this sort of attention, you shouldn’t be using biometrics, since they aren’t secure enough at that risk level in our opinion.

    Padlock sitting on a laptop

    Face ID is more secure from a brute force perspective according to Apple’s numbers. With a one-in-a-million chance of a random person looking enough like you. Identical twins are perhaps the exception here. So what about photographs or masks that replicate your face? Face ID has countermeasures for this. As mentioned above, photos won’t work since the camera can sense depth. It uses neural net technology to also mitigate against the use of masks.

    There are no numbers to tell us how effective this is, but once again for the average user, no one is going to spend thousands or even millions of dollars creating technology to defeat Face ID. If you’re the president of a country, don’t use biometric locks.

    Activating The iOS Biometric Killswitch

    Now only one issue remains. What if someone is in a position to force you into unlocking your phone? They just have to point it at your face or put your finger on it, after all. If you think you may be entering this situation, you can simply click the on/off button five times and biometrics will be disabled in favor of a passcode.

    Drawing of someone's face with biometric ID sensor points

    On the iPhone 8 and up you need to squeeze the side button and either of the volume buttons. These methods could be different when you read this, so be sure you look up the biometric killswitch method for your specific iOS device.

    In short: Face ID and Touch ID are plenty secure for most people, but not for people who need military-grade security. If you are however very paranoid, use a six-digit passcode instead.