Strong secrecy in bidirectional relay networks

To increase the spectral efficiency of future wireless networks, it is important to wisely integrate multiple services at the physical layer. Here we study the efficient integration of confidential services in bidirectional relay networks, where a relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase the relay transmits an additional confidential message to one node while keeping the other node completely ignorant of it. We use the concept of strong information theoretic security to ensure that the non-legitimate node cannot decode the confidential message no matter what its computational resources are. This results in the study of the bidirectional broadcast channel with confidential messages for which we establish the strong secrecy capacity region.