Active eavesdropping in fast fading channels

In this paper we study the problem of active eavesdropping in fast fading channels. The active eavesdropper is a more powerful adversary than the classical eavesdropper. It can choose between two functional modes: eavesdropping the transmission between the legitimate parties (Ex mode), and jamming it (Jx mode) - the active eavesdropper cannot function in full duplex mode. In this paper we only consider the best-case scenario, when the transmitter knows the eavesdropper´s strategy in advance - and hence can adaptively choose an encoding strategy. We show that, even under these most optimistic assumptions, an active eavesdropper can induce moderate to severe degradation of the achievable secrecy rate.