CLoRa-A Covert Channel over LoRa PHY

LoRa adopts a unique modulation scheme (chirp spread spectrum (CSS)) to enable long range communication at low power consumption. CSS uses the initial frequencies of LoRa chirps to differentiate LoRa symbols, while simply ignoring other RF parameters (e.g., amplitude and phase). Driven by this observation, we build a covert channel (named CLoRa) by embedding covert information with a modulation scheme orthogonal to CSS. We implement CLoRa with a COTS LoRa node (Tx) and a low-cost receive-only SDR dongle (Rx). The experiment results show that CLoRa can send covert information over 250 m. This demo reveals that the LoRa physical layer leaves sufficient room to build a covert channel by embedding covert information with a modulation scheme orthogonal to CSS.