The Fifth Amendment, which protects people from incriminating themselves during legal proceedings, prevents the government from compelling someone to turn over a memorized PIN or passcode. But fingerprints, like other biometric indicators—DNA, handwriting samples, your likeness—have long been considered fair game, because they don’t reveal anything in your mind. (Marcia Hofmann, a digital-rights lawyer, wrote a comprehensive rundown of the question in late 2013, when it was still hypothetical.)
Now that it’s clear that police are willing to ask for warrants for phone-unlocking fingerprints—and that judges are willing to sign them—security-conscious smartphone users are faced with a menu of mostly unsavory options.
A fingerprint and a long passcode provides a good balance between convenience and security—or it did, until courts began compelling fingerprint unlocks, said Chris Soghoian, the chief technologist at the American Civil Liberties Union. The alternatives are worse: A short PIN “lets you use your phone like a human,” Soghoian said, but can be guessed by a computer algorithm in certain cases. And a long passcode, while secure, is a pain to type in every time you want to check Tinder.