Modern smartphones are equipped with a plethora of sensors that enable a wide range of interactions, but some of these sensors can be employed as a side channel to surreptitiously learn about user input. In this paper, the authors show that the accelerometer sensor can also be employed as a high-bandwidth side channel; particularly, we demonstrate how to use the accelerometer sensor to learn user tap and gesture-based input as required to unlock smartphones using a PIN/password or Android’s graphical password pattern.
You can download it from the following link: https://packetstormsecurity.com/files/download/119906/aviv-acsac12-accel.pdf
Source: https://packetstormsecurity.com/files/119906/Practicality-Of-Accelerometer-Side-Channels-On-Smartphones.html