Considering the nationwide panic regarding security and privacy, both offline and online, Apple’s new Touch ID system was met with some cynicism. Where is the fingerprint data going to be stored? What happens if someone obtains the data? Would a criminal be willing to remove my finger in order to access my contact list? Some concerns were admittedly a bit more hypothetical than others, but Marcia Hofmann’s piece on Wired brings up a legal situation which is far more likely to cause problems for an iPhone owner than the theoretical digit thief.
The Fifth Amendment provides the right against self-incrimination in a court of law. A judge may not require the defendant to incriminate him or herself with any information that is testimonial, or as Hofmann puts it, “reveals the contents of your mind.” That would include, say, the four-digit code to unlock your iPhone 5, but if access to your iPhone 5s depends on your fingerprint, that could be seen as physical evidence.
Hofmann provides a classic example that illustrates a similar case.
“Take this hypothetical example coined by the Supreme Court: If the police demand that you give them the key to a lockbox that happens to contain incriminating evidence, turning over the key wouldn’t be testimonial if it’s just a physical act that doesn’t reveal anything you know,” Hoffman wrote. “However, if the police try to force you to divulge the combination to a wall safe, your response would reveal the contents of your mind — and so would implicate the Fifth Amendment.”
The switch from “knowledge based authentication” to biometric authentication is certainly an exciting one, but it’s worth keeping in mind the potential consequences when you unlock your phone with your thumb instead of a password.