Feedback Enhances the Security of State-Dependent Degraded Broadcast Channels With Confidential Messages

In this paper, we investigate the state-dependent degraded broadcast channels with confidential messages (SD-DBC-CM), and with or without noiseless feedback. In this new model, the channel state is available at the transmitter in a noncausal or causal manner, and there may exist a noiseless feedback link from the nondegraded receiver to the transmitter. For the discrete memoryless SD-DBC-CM, inner and outer bounds on the capacity-equivocation regions are provided for both the noncausal and causal cases. For the discrete memoryless SD-DBC-CM with feedback, inner and outer bounds on the capacity-equivocation region are provided for the noncausal case, and the capacity-equivocation region is determined for the causal case. The results of this paper are further explained via Gaussian and binary examples.