Wiretap-channels with constrained active attacks

In this paper, we calculate an achievable secrecy rate for the Wiretap Channel (WTC) with an active eavesdropper, who is subject to a distortion constraint, in general. Furthermore, we consider the replacement attack and jamming attack explicitly, when imposing symbol, peak or an average constraint on the jamming sequence. We show, that in all cases the optimal strategy for the eavesdropper is to disturb each symbol equiprobable in the former case, or to jam each symbol with the same jamming power in the latter case. A consequence is, that the eavesdropper´s replacement attack can be modeled as an additional Binary Symmetric Channel (BSC). Additionally, we demonstrate, that if the attacker is able to induce a channel corruption which corresponds to his own channel´s degradedness or which is even worse, no positive secrecy rate is achievable.