Hidden in Plain Sight: Communicating using Interference

Radio astronomy observatories examine the universe by capturing faint RF signals from space. The equipment to capture these signals is extremely sensitive, and nearby transmitters, such as LEO satellites, cause destructive interference. We propose the Spectra watermarking protocol to add an identifying fingerprint to these interfering transmitters. Spectra changes the timing of key transmissions to encode identifying information that can be decoded by examining transmission timestamps and without having to demodulate the actual transmission. We implement multiple forward error correction codes for Spectra to account for dynamic LEO satellite channels. We evaluate Spectra and show that it can operate over highly variable channels with low BER while preserving the network performance of the interfering device.