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the whole view of the experiment was taken by a handheld video camera (see NICT’s press release “Development of relaying video data by a drone with perfect secrecy” (only in Japanese): http://www.nict.go.jp/press/2017/03/22-1.html)e videos were reproduced smoothly in real time at the ground station without drop-frames (loss of image data). e phenomenon of paused reproduction of video data seen in the open-air experiment did not occur. From the above, the functions of video relay and encryption and decryption of the video were conrmed to work without problems under not only outdoor but also indoor environ-mental conditions.7Prospects for the futureIn the future, we will promote the development of compact and reliable encryption and decryption devices. Also, we will conduct experiments to study the distribution of radio wave intensity in the data transmission with the system of the components we used for these experiments, by conducting a communication experiment in a non-echoic chamber which will be utilized in developing technologies of relaying data. Moreover, we will develop technologies to construct a exible relaying network for various purposes and large areas by increasing both cam-eras and relay drones, as well as continue implementing experiments on reliability to utilize for monitoring key facilities which it is dicult for humans to enter.ReferenceR1T. Itoh, et al. “Security Enhanced Drone Control System and Its Application,” IEICE Society Conference 2016 – Engineering Sciences Society / NOLTA Society, AI-3-5, SS-33, Sept. 2016.2T. Itoh, et al. “Highly Secure Drone Communications Network,” IEICE General Conference 2017, AI-3-2, SS-50, March 2017.3C. E. Shannon, “Communication Theory of Secrecy Systems,” Bell System Technical Journal, vol.28(4), pp.656–715 (1949).4M. N. Wegman and J. L. Carter, “New hash functions and their use in authen-tication and set equality,” Journal of Computer and System Sciences, vol.22, no.3 pp.265–279 (1981).Ryoji NISHIZAWA Engineer, Quantum ICT Advanced Development Center, Advanced ICT Research InstituteUAV communicationsKazuo ICHIHARA Managing Director, Prodrone Co., Ltd.UAV controls & communicationsToshiyuki ITOH, Ph.DResearcher, Quantum ICT Advanced Development Center, Advanced ICT Reseach InstitutePhysical layer cryptography, Free space optical communicationMikio FUJIWARA, Ph.DResearch Manager, Qunatum ICT Advanced Development Center, Advanced ICT Reseach InstituteQuantum key distribution, Photon detection techology, Cryogenic electronicsFiF6Configuration of indoor experiment. Operators were assigned for manual operation of drones. (between ground station and relay drone, the distance between each drone is about 10 meters)StageFoyerWallDoor openCorridorStepsDoorObstacleObject17m20mFlying to approach to the objectDoorDoorDoorDoorDoor*Height of ceilinginside the building : 7mGroundstationCamera droneRelay droneTrans-mitting video data to relay droneTransmitting video data to ground station3 Quantum Key Distribution Network46　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 1 (2017)