A man with one hand in his pocket approaches a locked door and places his other hand on the doorknob. A second later, the deadbolt clicks open, as if by magic, and he lets himself in. A would-be burglar casing the house watches this sequence of events unfold. The next day, after the man has left for work, the burglar approaches the door and places his hand on it, expecting it to pop open. Instead, it stays stubbornly locked. It’s not outfitted with a typical “smart lock,” which uses Wi-Fi or Bluetooth to open when a paired phone or watch is nearby. It’s not reading his fingerprint, either. So what’s going on?
A similar scenario recently unfolded in the University of Washington’s Networks and Mobile Systems Lab, where researches are experimenting with a new technology that sends passcodes through the human body. The technology uses touchpads and fingerprint readers to create signals that travel through skin—and, unlike wireless broadcasts, the “on-body” transmissions can’t be intercepted over the air.
Using their method, a person just needs to be touching a transmitter—the fingerprint reader on an iPhone, for example—when he or she comes in contact with a receiver. In the doorknob example, the metal handle is hooked up to a reader that listens for electromagnetic pulses. A code sent from the iPhone’s fingerprint reader travels across a layer of particularly conductive tissue right beneath the outer layer of human skin. It quickly propagates to every part of the body, so that your entire epidermis glows, invisibly, with data. (The researchers were able to detect signals sent from one arm to the opposite leg, and could accurately read them whether the person was standing, sitting, or lying down.) When the signal arrives at the doorknob, the reader makes sure it’s the right passcode and, if it is, it opens.