UAV-Assisted Quantum Key Distribution for Secure Communications with Resource Limited Devices

One-time-pad (OTP) can provide unconditionally secure communications between devices with limited resources, but requires continuous key distribution. Existing quantum key distribution (QKD) protocols produce a continuous secret key stream, but cannot be deployed at the devices that have no quantum channels. In this paper, we first propose a scheme, called synchronized random measurement (SRM) to improve the secret key rate of a QKD protocol. Then, we further propose the novel idea of using unmanned aerial vehicles (UAV) as a physical courier to carrier secret key bits generated through QKD at a gateway to all control devices within coverage area of the gateway. When the UAV does not visit a control device to replenish its consumed secret key bits before the bits are depleted, the device suffers from key deficiency and secure communications are interrupted. We formulate an optimization to minimize the number of UAVs needed to cover all control devices, taking into account the limited battery capacity on-board UAVs and the key deficiency requirement. Through simulations, we have confirmed the key quality and rate improvement of the proposed SRM. We have also evaluated the proposed optimization in finding the minimum number of UAVs to cover different numbers of control devices within a gateway coverage area of different sizes. Increasing the coverage area diameter beyond the UAV flight range may require as many UAVs as the number of control devices for a complete service.