If you value the security of your data — your email, social media accounts, family photos, the history of every place you’ve ever been with your phone — then I recommend against using biometric identification.
Instead, use a passcode to unlock your phone.
Numeric Passcodes: hard to guess, easy to change, and legally protected
With iPhones, you only get 10 attempts to unlock a phone with a passcode.
Assuming your passcode is a 4-digit numeric PIN, there are 10⁴ possible combinations. That means someone trying to unlock your phone has a one-in-a-thousand chance of successfully unlocking your phone.
This may not sound as secure as the “one in a million” figure Apple toted as the likelihood that someone could look similar enough to you to unlock your iPhone. But with your numeric passcode, an attacker has nothing to go on. They have no idea what that number could be. If it’s truly random, this would make it more secure than Face ID.
Most phones — including iPhone — support multi-digit passcodes. Each extra digit gives you an order of magnitude of extra security. But considering that you will be entering this many times a day, 4 digits may be the more sustainable choice here.
And to be clear, a court in the US cannot force you to give up your passcode. That passcode exists in your head, and yours alone. It is your property, and won’t be used to incriminate you or strong-arm access to your data unless you voluntarily give it up.
The security and peace of mind you get from a passcode is well worth the 2 seconds it takes to enter it.
The way forward for biometric identification
Instead of the current all-or-nothing approach — you’re either authenticated or you aren’t — device manufacturers should take a tiered approach, requiring different levels of authentication to access different apps and data.
This is similar to traditional role-based access control in software. And phones already do this with lock screens.
For example, by default on iOS, you can read incoming text messages without unlocking your phone. And whenever you try to buy something in the App Store, iOS by default requires you to enter an even longer password to confirm a purchase.
Something like Face ID could be used to unlock your “read” permission to use less sensitive apps where you consume information, such as newspaper apps.
But then when you want “write” permission so you can send a text or post a tweet, your phone could require you to enter a passcode.
This is a software change that could be rolled out to all iPhones — including ones that people are already using. And doing so would make everyone much more secure.
There is a sweet spot on the security-convenience continuum. But unlocking your entire phone — and all the data, social media accounts, and bank accounts that comes with it — with just your face? We still have a ways to go before we reach that sweet spot.
For now, my advice is to continue using passcodes, and to make sure they’re strong passcodes.