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1Background of developmente quantum ICT advanced development center has already succeeded in a demonstration experiment of en-crypted control communication using a drone. e control communication of the drone is performed at a low rate of several hundred Kbps, so it was relatively easy to imple-ment the concealing of data perfectly by using One-time Pad (OTP) encryption. On the other hand, a large volume of data such as videos between drones or between a drone and a ground station is transmitted at a high rate of sev-eral Mbps to several tens of Mbps. Hence, a technology to prepare a large amount of random number sequences and synchronize them as keys is necessary. A technology of relaying video via a drone as a wireless repeater is also necessary, because drones for monitoring key facilities or keeping watch over large-scale events need to move around wide areas to capture videos of them. So, we started to develop these technologies.2OTP encryption and true random numbersOTP encryption is a method in which both a sender and a receiver share a true random number sequence as an encryption/decryption key and the sender encodes a plain-text message by applying exclusive OR (XOR) with the encryption key, and the receiver decrypts it by XOR with the same key. Aer each communication completion, both the sender and the receiver dispose of the used encryption keys as if peeling post-it notes. is method is only one encryption protocol which is certied as information theo-retically secure [3]. Also, as XOR at the encryption and decryption is a simple process, the calculation could not be delayed if only true random number sequences whose sizes are the same as that of the data (plaintexts) are shared.e load capacity of a drone for small distributions is about 5 kilograms and its battery life is about 20 minutes, so the size of the onboard computer is limited in general. e security of public key encryption widely used today depends on the computational complexity, so if the capac-ity of the computer is limited, the calculation delays or radio interference due to these delays may deteriorate the communication quality. Also, simpler encryption devices increase the risk of decryption by powerful computers. By using OTP encryption, we can conduct information theo-retically secure communications without constraints due to a limitation of the capacity of computers until the supplied true random number sequences are used up.e true random number sequence is a sequence of completely random numbers without any regularity or reproducibility. Random numbers generated by a device which adopts unpredictable physical phenomena such as thermal noise or quantum mechanical phenomena have such a property. As generation rates with such generation methods are low, pseudo-random numbers generated by a determined computational algorithm are used for most cases of cryptography in general. However, pseudo-random number sequences have periodicity and powerful comput-ers can decrypt such cryptography. erefore, true random 3-4 Secure Transmission of Video Data Relayed by UAVRyoji NISHIZAWA, Kazuo ICHIHARA, Toshiyuki ITOH, Mikio FUJIWARA, and Masahide SASAKIHighly-secure communications with One-Time Pad (OTP)encryption for controls of UAVs was demonstrated in the automatic-book-delivery experiment by UAV which was implemented at Senpoku-city in Akita prefecture on 12th April, 2016 [1][2]. At that time, random numbers used in OTP were provided from the physical random number generator. By using this technology, we newly develop technologies of relay and transmission of OTP encrypted video-data from an UAV with a camera to the ground station relayed by another UAV. Both field experiment which simulated monitoring an outdoor facility, and the indoor experiment which simulated searching missing-person at the time of disaster, were accomplished successfully. In this paper, contents of this development, mainly, and also these experiments are described.413 Quantum Key Distribution Network