Wireless physical layer key generation scheme based on unscheduled forwarding signal

Wireless physical layer key generation is a remarkable technology for physical layer security. The security of key generation is not guaranteed in existing wireless physical layer key generation schemes if the eavesdropper is less than half a wavelength away from the legitimate node, which called non-secure zones problem. To address this problem, this paper proposes a Wireless physical layer key generation scheme based on unscheduled forwarding signal (WKG-UFS). Specifically, the legitimate communication nodes send random signals to each other within a coherent time. Then, the received signals are forwarded back within the coherent time after a random time interval. The legitimate nodes estimate the equivalent channel based on the final received signal and generate the secure key. Since eavesdropper does not know the original signals sent by the legitimate communication nodes, the channel feature cannot be effectively estimated. The results of theoretical analysis and experimental simulation show that the proposed scheme can effectively reduce the threat of eavesdropping on secure communication. Besides, since the time intervals for receiving and forwarding signals are variable, it can also effectively resist active attacks which by manipulating the channel.