Key agreement in state-dependent channels with non-causal side information

Key agreement problem over a discrete memoryless state-dependent wiretap channel (DM-SWC) is addressed in this paper. Three parties have access to the wiretap channel: One transmitter, an authorized receiver, and an illegal receiver. The transmitter fully knows channel state information (CSI) in a non-causal form, while each receiver has access to a sequence of side information (SI) correlated with the CSI. Further to the DM-SWC, the parties can also exploit a unilateral public channel with a given capacity from the transmitter to the receivers. We have obtained a lower bound (LB) on the key capacity. The LB achieves the key capacity when the capacity of the public channel exceeds a fixed finite value determined by the DM-SWC. For any DM-SWC, the key capacity is consequently achievable as the public channel capacity becomes unlimited. An upper bound (UB) on the key capacity is obtained when the legal receiver is less noisy than the wiretapper.