Mobile token-based authentication on a budget

Abstract

We propose a light-weight, cheap authentication device for unlocking a user's smartphone. The device can be carried on a key chain and automatically unlocks the smartphone whenever its owner wants to use it. Our goal is to build a device that works with existing smartphones, requires no recharging or maintenance, and is always available. We propose two approaches: one based on magnetic fields detected by the smartphone's compass and the other based on an acoustic transmitter that generates a signal picked up by the handset's microphone. We experiment with both approaches and report on their effectiveness. These devices may find applications beyond smartphones, such as unlocking laptops, cars, and homes. These designs show that contactless authentication can offer a convenient and secure alternative to PIN-based unlocking.