On the secrecy capacity region of a class of parallel Wiretap Broadcast Channel

This work investigates the secrecy capacity region of a class of Wiretap Broadcast Channel (WBC) where a source wishes to send two independent messages to two receivers in the presence of an external eavesdropper. We focus on the class of parallel WBC and more precisely on the product of two reversely less-noisy BC with a more noisy eavesdropper. We fully characterize the capacity region of such a setting through a novel powerful outer bound that relies on a careful single letter expression, followed by a non-trivial equivalent formulation of the resulting rate region. This outer bound turns out to be tight with the inner bound we derive for the setting under study.