Establishing a covert communication channel in RF and mm-wave circuits

A method is proposed to implement a hardware Trojan that can be used to leak confidential information in RF and mm-wave circuits. The method modifies the input impedance matching network of a power amplifier by using a single nMOS transistor. Input matching of the power amplifier changes with digital data that is covertly transmitted and this slight change (0.63 dB) is observed at the output gain of the power amplifier, which ultimately changes the power level of the signal that arrives at the receiver. The inserted nMOS transistor and interconnections are hidden under transmission lines and ground planes, making them invisible to the user. The efficacy of the proposed methodology is demonstrated by using full EM simulations of a 77 GHz power amplifier that was previously fabricated and measured. Performance parameters of the power amplifier remain within expected process variations, as verified via Monte Carlo simulations. To the best of authors' knowledge, the proposed work demonstrates the first hardware Trojan method that enables covert communication, designed specifically for mm-wave circuits