A full-duplex active eavesdropper in mimo wiretap channels: Construction and countermeasures

We examine the design of a full-duplex active eaves-dropper in the 3-user MIMOME wiretap channel, where all nodes are equipped with multiple antennas. The adversary intends to optimize its transmit and receive sub-arrays and jamming signal parameters so as to minimize the MIMO secrecy rate of the main channel. The full-duplex operating mode of the adversary induces self-interference at its receive sub-array, which is factored into the adversary's optimization. We characterize the worst-case jamming covariance for arbitrary and Gaussian input signaling, and develop a numerical algorithm to compute the same. We then examine sub-optimal active eavesdropping schemes that comprise essentially an antenna subset selection problem for the adversary, followed by a brief discussion of a potential countermeasure where the transmitter allocates some of its spatial dimensions for jamming the eavesdropper. Numerical results are presented to verify the efficacy of the proposed adversarial optimization algorithms.