Wiretap Channels: Implications of the More Capable Condition and Cyclic Shift Symmetry

Characterization of the rate-equivocation region of a general wiretap channel involves two auxiliary random variables: U, for rate splitting and V, for channel prefixing. Evaluation of regions involving auxiliary random variables is generally difficult. In this paper, the authors explore specific classes of wiretap channels for which the expression and evaluation of the rate-equivocation region are simpler. In particular, they show that when the main channel is more capable than the eavesdropping channel, V = X is optimal and the boundary of the rate-equivocation region can be achieved by varying U alone.