Imaging Privacy Threats from an Ambient Light Sensor
First-ever imaging privacy threats from non-imaging components (ambient light sensors) of smart devices. An idea inspired by George Orwell's dystopian novel 1984 -- "Big Brother is watching you" through a two-way TV-like telescreen.
Embedded sensors in smart devices pose privacy risks, often unintentionally leaking user information. We investigate how combining an ambient light sensor with a device display can capture an image of touch interaction without a camera. By displaying a known video sequence, we use the light sensor to capture reflected light intensity variations partially blocked by the touching hand, formulating an inverse problem similar to single-pixel imaging. Due to sensors’ heavy quantization and low sensitivity, we propose an inversion algorithm involving an ℓp-norm dequantizer and a deep denoiser as natural image priors, to reconstruct images from the screen’s perspective. We demonstrate touch interactions and eavesdropping hand gestures on an off-the-shelf Android tablet. Despite limitations in resolution and speed, we aim to raise awareness of potential security/privacy threats induced by the combination of passive and active components in smart devices, and promote the development of ways to mitigate them.
