26. A Gentle Introduction to Side Channel Attacks on Smartphones

To sustain a wide range of applications, to attract app developers, and to foster innovation, smartphones come bundled with a plethora of sensors and peripherals that apps can use: an accelerometer for sensing movements, a gyroscope for sensing orientation, a magnetometer for sensing magnetic fields, a camera for taking pictures, and so on. Although initially considered innocuous, researchers have repeatedly demonstrated that sensors leak unintended information. These leaks could help malicious apps reconstruct banking PINs, Dual-Tone Multi-Frequency tones or spoken secrets. In this chapter, we provide an introduction to such attacks by reviewing their principles and effectiveness. We then illustrate them through two recent research papers. Such attacks are currently in their early stage. But we hope to raise awareness of their existence amongst practitioners, as they are likely to become more effective and prevalent on smart mobile platforms in the future.