Is Your FPGA Transmitting Secrets: Covert Antennas from Interconnect

A hidden transmitter embedded into a chip to extract secret information is a well-known type of hardware Trojan. Various ways of implementing covert channels have been proposed in the past. The focus of this paper is covert antennas created from the FPGA interconnect. We present several on-chip antenna implementations that leverage the routing resources of FPGAs. The proposed antennas can transmit data processed by the FPGA with bit-level precision. A near-field probe is used to capture the radiated signal and the transmitted data is restored with 100% accuracy. Our results suggest that introducing a routine screening process for covert antennas in FPGA designs, similar to the one performed for ring oscillators, would be of benefit for FPGA security.