CICS Researchers Demonstrate Security Flaw in Visible Light Communication

Assistant Professor Jie Xiong of the UMass Amherst College of Information and Computer Sciences (CICS), along with CICS doctoral students Minhao Cui and Yuda Feng, have been recognized with a Best Paper Honorable Mention award for “Sniffing Visible Light Communication Through Walls,” presented at the 2020 ACM MobiCom conference in September.

Co-authored with Qing Wang of the Delft University of Technology, the paper demonstrates how visible light communication (VLC) technology—widely considered to be a secure communication method in indoor settings, where it is being considered for inclusion in next-generation 6G wireless networks—can in fact be eavesdropped more easily than previously believed.

In their paper, the team shows for the first time that VLC transmissions can be “sniffed through walls,” due to the fact that VLC transmitters emit not only visible light, but low frequency electromagnetic signals that cannot be blocked by walls. 

While turning a visible light source (such as an LED) on and off, a VLC transmitter inevitably changes the flow of electrical current in its power line, which induces a changing magnetic field. With a receiver designed to capture the magnetic field changes and decode them, the researchers discovered that VLC transmission can be eavesdropped even when the visible light itself is secured by a wall.

Using a cheap, small, handmade copper coil, the researchers were able to use this technique to simultaneously decode multiple VLC transmissions with their “sniffer” through a wall and over 20 feet away. They were also able to sniff VLC transmission signals at shorter distances using the wireless charging coil built into a smartphone, showing the possibility of creating VLC eavesdropping devices out of widely available technology.

Xiong joined CICS in 2018, and is affiliated with the UMass Amherst Institute for Applied Life Sciences, which provided support for this project. His research interests are in sensor-free and contact-free wireless sensing, mobile health, and wireless networking.

Explore the paper or watch the presentation from MobiCom 2020.