AudioKey: A usable device pairing system using audio signals on smartwatches

Abstract

Smartwatches are expected to replace smartphones in some applications with better user experience because of a greater range of features and new innovations such as audio recording, activity recognition, and data transmission. In this paper, we develop a system called AudioKey, aiming to pair two smartwatches by generating a unique secret key between them. Compared with existing works, our system does not need extra infrastructure to synchronise devices and trigger the key generation process, and only uses the existing sensors (gyroscope and microphone) that are deployed on most smartwatches. AudioKey triggers the key generation process on two devices at the same time by detecting the handshake between two normal users. A secret key is extracted from both the frequency domain and the time domain of audio signals and used to authenticate each other or encrypt the sensitive data. Evaluation results collected on nine volunteers in three different scenarios show that our system can achieve a bit generation rate of 13.4 bits/s with the mean key agreement rate of 96.7% for a 128-bit secret key, while a strong attacker can only achieve a mean key agreement of 10.8%.