Acoustic Emanation of Haptics as a Side-Channel for Gesture-Typing Attacks

In this paper, we show that analysis of acoustic emanations recorded from haptic feedback during gesture-typing sessions is a viable side-channel for carrying out eavesdropping attacks against mobile devices. The proposed approach relies on acoustic emanation resulting from haptic events, namely the buzz of a small vibration motor as the finger initiates the gesture-typing of a work in a sentence. By analysing time between haptic feedback events, it is possible to identify the text that a user enters via the soft keyboard on their device. The attack requires no prior interaction or need to install software on the target device (unlike similar works); only the ability to record audio within the vicinity. We present an experimental framework to illustrate the feasibility of the attack. In the experiments we show that sentences can be detected with an accuracy of 70% with some sentences identified with up to 95% accuracy. The attack can be conducted with minimal computation and on non-specialist consumer equipment. The paper concludes by proposing a number of countermeasures that mitigate the ability of an attacker to successfully intercept keyboard input.