New results on Secret Key Establishment over a pair of broadcast channels

Secret Key Establishment (SKE) over a pair of independent Discrete Memoryless Broadcast Channels (DMBCs) was studied in where lower and upper bounds on the secret-key capacity were provided. In this paper, we study the above setup for two cases: (1) the DMBCs have “secrecy potential”, and (2) the DMBCs are stochastically degraded with independent channels. For (1), we propose a simple SKE protocol using the novel Interactive Channel Coding (ICC) method and prove that it achieves the lower bound. For (2), we give a simplified expression for the lower bound and prove that, when one of the legitimate parties sends only i.i.d. variables, the lower bound is tight and the capacity is achieved by a two-round protocol.