In collaboration with Technische Universit¨at M¨unchen

Cooperative broadcast channels with a secret message

Z. Goldfeld, G. Kramer and H. H. Permuter

In Proceedings of the 2015 IEEE International Symposium on Information Theory (ISIT-2015), Hong-Kong, June 2015

The broadcast channel (BC) with one confidential message and where the decoders cooperate via a one-sided link is considered. A pair of messages is transmitted, one message for
each user. The message to the cooperative user is confidential and is kept secret from the cooperation-aided user. The secrecy level is measured by the equivocation rate. An inner bound on the secrecy-capacity region of the BC is derived. The inner bound is achieved by double-binning the codebook of the secret message. The inner bound is tight for the semi-deterministic (SD) and physically degraded (PD) cases. The secrecy results are compared to those of the corresponding BCs without a secrecy constraint. A cooperative Blackwell channel example illustrates the impact of secrecy on the rate regions.