Polar Coding for the Wiretap Broadcast Channel with Multiple Messages

A polar coding scheme is proposed for the Wiretap Broadcast Channel with two legitimate receivers and one eavesdropper. We consider a model in which the transmitter wishes to to reliably send different confidential and private messages to the different legitimate receivers, and the confidential message must also be (strongly) secured from the eavesdropper. There are two different inner-bounds on the achievable region of this model in the literature. Both are characterized by using Marton's coding and the only difference between them is the decoding strategy: one is characterized by using joint decoding, while the other uses successive decoding. In this paper we present a polar coding scheme that achieves the larger inner-bound, and we show that polar-based joint decoding is crucial for this purpose. A full version of this paper is accessible at: https://arxiv.org/abs/1909.04898