A Physical-Layer Security Based on Wireless Steganography Through OFDM and DFT-Precoded OFDM Signals

We propose a physical-layer security approach based on the concept of steganography for IoT networks. Similar to the covert communications, the transmitter (Alice) attempts to send her secret signal to the legitimate receiver (Bob) avoiding being detected by the warden (Willie). Instead of sending the weak signal that is barely detectable by Willie, we hide secret signal in the cover signal that is transmitted over the same channel such that its existence may not be easily detected without any knowledge of prior information. Considering the practical applications to IoT networks, the DFT-precoded OFDM is adopted for the cover signal and conventional OFDM for the secret signal. Through theoretical analysis and corresponding simulations, the detection error probability of Willie is evaluated over an AWGN channel, revealing that judicious selection of cover signal power may increase the detection error probability of Willie and thus improve the covertness.