BLINDSPOT: Enabling Bystander-Controlled Privacy Signaling for Camera-Enabled Devices

TL;DR

BlindSpot introduces real-time, on-device privacy signaling methods for bystanders to control camera capture, using gesture, visible light, and UWB protocols, validated through comprehensive testing on smartphones.

Contribution

The paper presents three novel signaling modalities and a validation mechanism for privacy control, along with a complete implementation and evaluation on smartphones.

Findings

All modalities are feasible with acceptable accuracy and latency.

Gesture signaling is quick but less reliable in low light.

UWB offers high accuracy but requires specialized hardware.

Abstract

Camera-equipped mobile devices, such as phones, smart glasses, and AR headsets, pose a privacy challenge for bystanders, who currently lack effective real-time mechanisms to control the capture of their picture, video, including their face. We present BlindSpot, an on-device system that enables bystanders to manage their own privacy by signaling their privacy preferences in real-time without previously sharing any sensitive information. Our main contribution is the design and comparative evaluation of three distinct signaling modalities: a hand gesture mechanism, a significantly improved visible light communication (VLC) protocol, and a novel ultra-wideband (UWB) communication protocol. For all these modalities, we also design a validation mechanism that uses geometric consistency checks to verify the origin of a signal relative to the sending bystander, and defend against impersonation attacks. We implement the complete system (BlindSpot) on a commodity smartphone and conduct a comprehensive evaluation of each modality's accuracy and latency across various distances, lighting conditions, and user movements. Our results demonstrate the feasibility of these novel bystander signaling techniques and their trade-offs in terms of system performance and convenience.