Key generation through two-way relay channels under active attacks

Most of the existing work on key generation from wireless fading channels requires a direct wireless link between legitimate users so that they can obtain correlated observations from the common wireless link. Furthermore, most of the existing work assumes that the attacker is passive. This paper studies the key generation problem in the two-way relay channel, in which there is no direct channel between the key generating terminals, under active attacks. We propose an effective key generation scheme. We also investigate the effects of the active attacker on the proposed key generation protocol. We characterize the optimal attacker's strategy that minimizes the key rate of the proposed scheme. Furthermore, we establish the maximal attacker's power under which our scheme can still achieve a non-zero key rate.