JP6923151B2 - Signal transmission system by unmanned aerial vehicle - Google Patents

Description

According to the present invention, encryption key sharing via an unmanned aerial vehicle for sharing a common encryption key required for highly confidential broadcast encryption communication between a satellite or a large aircraft and a plurality of ground stations. It relates to a system, a signal transmission system by an unmanned aerial vehicle for transmitting a signal for such broadcast encrypted communication by an unmanned aerial vehicle, and an unmanned aerial vehicle applied to the system.

In recent years, unmanned aerial vehicles consisting of small drones (multicopters) capable of unmanned flight and unmanned helicopters have become widespread. This unmanned aerial vehicle is being used in various industries such as surveying, disaster relief, research on the natural environment, sports relay, delivery, and pesticide spraying. As the technology of this unmanned aerial vehicle continues to advance, it is expected that its usage will expand further.

In particular, this unmanned aerial vehicle has a wide range of cruising range and flight altitude, and is also capable of staying in an almost fixed position in the air, so that it has excellent characteristics in terms of maneuverability. In addition, unmanned aerial vehicles that can stay in the stratosphere for more than a few years using solar cells have also appeared. By connecting these unmanned aerial vehicles to satellite communications while utilizing them as base stations and relay stations, it is expected that a flexible and dynamic wireless communication network can be constructed over the space, stratosphere, high-altitude troposphere, and the ground. Efforts to improve communication connectivity are progressing.

In addition to this, it goes without saying that in a wireless communication network that includes an unmanned aerial vehicle as a relay node, in addition to improving convenience and connectivity, improving the information security of the entire system is required. When an unmanned aerial vehicle is used as a relay node for wireless communication, it is naturally possible to relay highly confidential information such as medical information, finance, and personal information from satellites and large aircraft. In communication networks for air traffic control of various aircraft, regardless of whether they are manned or unmanned, it is necessary to completely prevent unauthorized access and falsification of control signals, as well as the flow of highly confidential information. In addition, GPS (Global Positioning System) signals are often acquired from satellites when unmanned aerial vehicles are navigating, but if an unmanned aerial vehicle is hijacked and manipulated illegally by spoofing this GPS signal, the wireless communication network itself It leads to the collapse of.

Therefore, when the wireless communication network including this unmanned aerial vehicle is used for important purposes where information leakage, falsification, or unauthorized access is not allowed, it is required to construct a system with extremely high security in terms of security. Various cryptographic techniques have been studied in order to improve the security of wireless communication. Common cryptographic techniques currently in use are public key cryptography and symmetric key cryptography. Public key cryptography issues an electronic signature to authenticate and prevent tampering (ensuring integrity), and exchanges keys between necessary senders and receivers. Common key cryptography encrypts data communication at high speed based on the key (ensuring confidentiality). They are secured on the basis of certain mathematical algorithms that require enormous calculations to decrypt. However, cryptanalysis technology continues to advance to this day, and it is predicted that remarkable progress will be made in the future. For this reason, even if confidential information is encrypted with a cryptographic method that has sufficient strength at present and wireless communication is performed, the intercepted ciphertext can be stored for a long period of time, and more advanced cryptanalysis technology can be used in the future. When a high-performance computer is available, there is a risk that the ciphertext will be decrypted retroactively.

Therefore, in order to improve the information security of the wireless communication network including the unmanned aerial vehicle as the relay node, it is necessary to perform wireless communication based on the encryption technology that cannot be deciphered as much as possible. For this purpose, it is necessary to improve information security by applying at least a cryptographic technology that satisfies computational security. And in communication that handles important information, no matter how much computing power the attacker has, it can prove that it is impossible to decipher plaintext from ciphertext in principle, so-called information-theoretic security. It is strongly desired to use a cryptographic technology that satisfies the characteristics.

Conventionally, disclosure techniques of Patent Documents 1 and 2 and Non-Patent Document 1 have been proposed as a method of performing encrypted communication between a satellite or an aircraft and a plurality of ground stations. In the disclosure technology of Patent Document 1, a public key cryptosystem is used between a broadcasting station and a receiver so that only a receiver who is qualified to view the information can be decrypted by the broadcasting station using a satellite. A key delivery method for key sharing using the above has been proposed. Further, in Patent Document 2, a seed value for generating a pseudo-random number is given by using noise contained in observation data acquired from a sensor mounted on an artificial satellite, and a cipher that enables safe pseudo-random number generation in the artificial satellite. Communication technology has been proposed. Non-Patent Document 1 proposes a method for exchanging and managing an encryption key between an unmanned aerial vehicle and a plurality of ground moving objects based on public key cryptography. However, these disclosure technologies are based on cryptographic technology based on computational security, and cannot prevent security from being compromised with the progress of decryption technology.

In addition, from the viewpoint of network construction method, even if the ground stations are dispersed, the satellite and the plurality of ground stations can be relayed by multiple unmanned aerial vehicles in multiple stages in a hierarchical manner. It is possible to perform ultra-confidential encrypted communication to individual ground stations. The cryptographic communication technology proposed in Patent Documents 1 and 2 and Non-Patent Document 1 is not a technology premised on such a flexible and hierarchical network configuration.

For this reason, a technique for performing information-theoretic secure encrypted communication by relaying a plurality of unmanned aerial vehicles between a satellite and a plurality of ground stations has been conventionally desired.

Japanese Unexamined Patent Publication No. 11-340962 Japanese Unexamined Patent Publication No. 2014-62941

K.-H. Rhee, Y.-H. Park, and G. Tsudik, "A Group Key Management Architecture for Mobile Ad-hoc Wireless Networks," J. Inform. Sci. Eng., 21, 415-428 (2005) ). M. Bloch and J. Barros, "Physical-Layer Security," Cambridge University Press, 2011. O. Gungor, F. Chen, and C. E. Koksal, "Secret Key Generation Via Localization and Mobility," IEEE Trans. Vehicular Tech. 64 (6), 2214-2230 (June 2015). H. Liu, J. Yang, Y. Wang, Y. Chen, and CE Koksal, "Group Secret Key Generation via Received Signal Strength: Protocols, Achievable Rates, and Implementation," IEEE Trans. Mobile Computing, 13 (12), pp. 2820--2835 December 2014.

As a conventional cryptographic communication technology that can guarantee information-theoretic security, one-time pad cryptography based on key sharing on the ground has been proposed. In this proposed technology, a large amount of true random numbers common to each other are shared and stored in advance between a satellite or a large aircraft before flight and a ground station. Then, the plaintext is encrypted between the satellite or large aircraft after launch or takeoff and the ground station using the one-time pad encryption using the above-stored true random numbers. Since the encryption key is disposable each time, the information-theoretic security can be guaranteed as long as the encryption key can be shared securely.

However, in the cryptographic communication technology based on this one-time pad encryption, a large amount of intrinsic random number data that will not be exhausted for a long period of time is stored in advance, especially on the satellite side, and this is retained and managed in the space environment after launch. Is not easy. Ideally, a physical random number source should be mounted on the satellite side to constantly generate true random numbers within the satellite, but how to generate the true random number data between unmanned aerial vehicles and ground stations while guaranteeing information-theoretic security. The question of whether to share it still remains.

As another cryptographic communication technology for guaranteeing information-theoretic security, a method using physical layer cryptography has been conventionally proposed (see, for example, Non-Patent Documents 2, 3 and 4).

However, the disclosure technique described in Non-Patent Document 2 relates to pure mathematical research of proof of the theorem of information theory, and is specific for constructing a wireless communication network between a satellite or an aircraft and a plurality of ground stations. It does not offer a method. Further, the disclosure technique described in Non-Patent Document 3 implements a secret key exchange method by one-to-one wireless communication between vehicles, and is not intended for one-to-many broadcast encrypted communication. On the other hand, Non-Patent Document 4 discloses information on a protocol for sharing an information-theoretically secure encryption key and a demonstration experiment by incorporating a relay operation while coordinating between a plurality of wireless communication devices. However, this technology uses noise (random intensity fluctuation of the received signal) in the communication path of radio wave propagation as the source of encryption key generation, and the fluctuation speed of the source is limited to about kHz at most, so the key generation speed is extremely high. It has the drawback of being slow. Moreover, it is extremely difficult to secure such a random noise source between satellites and high-altitude aircraft. Further, this Non-Patent Document 4 does not present a hierarchical network configuration utilizing the navigation function of an aircraft.

In particular, since it is inevitably required for one satellite or aircraft to send and receive information not only to one ground station but to a plurality of ground stations, the effect expected in the present invention can be realized. The current situation is that the technical configuration has not yet been disclosed.

Therefore, the present invention has been devised in view of the above-mentioned problems, and an object thereof is to perform highly confidential broadcast encrypted communication between a satellite or a large aircraft and a plurality of ground stations. Above, an encryption key sharing system via an unmanned aerial vehicle that can be relayed via multiple unmanned aerial vehicles and can share a common encryption key that can guarantee information-theoretic security, as well as this It is an object of the present invention to provide a signal transmission system by an unmanned aerial vehicle for safely transmitting a signal for such broadcast encrypted communication without being intercepted by another unmanned aerial vehicle, and an unmanned aerial vehicle applied to the system.

The signal transmission system according to an unmanned aircraft according to the first invention, in the signal transmission system comprising a plurality of unmanned aircraft for relaying by sending transfer radio signals to a ground station having directivity sent large aircraft or al , each of the plurality of the unmanned aircraft to move in a range capable of receiving the radio signal, close to each other, deviating from the radio signal from the reception after the above-mentioned range, to transmit the radio signal to the ground station and wherein the relay child in Rukoto.

The signal transmission system according to an unmanned aircraft according to the second invention, in the first invention, satellite and, and the large aircraft flying at low altitude than the satellites, a plurality of the unmanned aircraft to fly at low altitude than the large aircraft 1 and hierarchy or unmanned aircraft layer containing respectively, and a plurality of the ground station, by the satellite to generate an initial random number R ₀ of the encryption key, which encrypts communication toward the large aircraft, the initial common to each other _{by 'between} the large aircraft and the satellite receiving the initial random number R ₀ and the random number R _0' random number R ₀ based on the random number R ₀ transmits and receives information about the mutual association of between Random number R _{ST is generated and shared, and the random number R LA} ^(k) based on the random _{number R ST} is encrypted and communicated with the ground station by relaying the unmanned aircraft layer from the large aircraft to the random number R. _LA and information about mutual association among the R _ST said random number, each held between each ground station and the satellite, which has received the random number R _{n ^(k)} based on ^_(k) R _{n ^(k)} It is characterized in that a random number R common to each other is generated by transmission / reception and shared.

The signal transmission system according to an unmanned aircraft according to the third invention, in the first invention, and the large aircraft, a plurality of the unmanned aircraft 1 hierarchy or unmanned aircraft layer containing respectively to fly low altitude than the large aircraft, and a plurality of the ground station, the by large aircraft to generate an initial random number R _ST of encryption key, and encrypted communication toward the unmanned aircraft layer made it from one level or more, based on the initial random number R _ST transmits and receives information regarding each other relevancy between the initial random number R _ST and the random number R _{ST ^(k)} between the random number R _{ST ^(k)} multiple received a between the unmanned aircraft and the large aircraft _{By generating and sharing a random number R HA} common to each other, and relaying the unmanned aerial vehicle layer, the _{random number R LA} ^(k) based on the random _{number R HA} is encrypted and communicated with the ground station, and the random number R is communicated with the ground station. Regarding the mutual relationship between the _{random number R n} ^(k) and the random number R _HA held by each ground station receiving the random number R _n ^(k) _{based on LA} ^{(k) and the large aircraft.} It is characterized in that a random number R common to each other is generated by transmitting and receiving information and shared.

The signal transmission system according to an unmanned aircraft according to the fourth invention, in any one of the second invention or the third invention, the unmanned aircraft in the large aircraft or the unmanned aircraft layer, communication characteristics of the communication channel before transmission of the random number Is evaluated, and it is determined whether or not to transmit the above random number based on the evaluation result of the above communication characteristics.

Further, with respect to the second invention, more specifically, one or more levels of unmanned aircraft including a satellite, a large aircraft flying at a lower altitude than the satellite, and a plurality of unmanned aircraft flying at a lower altitude than the large aircraft. A stratospheric link that has an aircraft layer and a ground station and transmits a random number for an encryption key from the satellite to the large aircraft, a relay link that transmits the random number from the large aircraft to the unmanned aircraft layer, and the unmanned. It is equipped with a ground link that transmits the above random number from the aircraft layer to the above ground station, _{generates an initial random number R 0} for the encryption key by the above satellite, performs cryptographic communication with the above large aircraft, _{and performs the above initial random number R 0.} By transmitting and receiving information on the mutual relationship between the _{initial random number R 0} and the random number R ₀ ′ between the large aircraft and the satellite that received the random number R _{0 ′ based on} and stratosphere link step of sharing this generates a _ST, then the cryptographic communication to the plurality of first unmanned aircraft the random number R _ST from the large aircraft in the first unmanned aircraft layer, based on the random number R _ST between the random number R _ST ^(k) the first respective unmanned aircraft and the large aircraft that receives the transmitting and receiving information about the mutual association of between the random number R _ST and the random number R _ST ^(k) was A high-altitude link step that generates and shares a common random number R _{HA with each other, and a first that flies the random number R HA} from one of the first unmanned aircraft at a lower altitude than the first unmanned aircraft layer. The second unmanned aircraft and the first unmanned aircraft that received the random number R _HAk ⁽ⁱ⁾ _{based on the random number R HA} by performing cryptographic communication with the plurality of second unmanned aircraft in the second unmanned aircraft layer. By transmitting and receiving information on the mutual relationship between the _{above-mentioned random number R HA} and the above-mentioned random number R _HAk ⁽ⁱ⁾ with the aircraft, the random numbers R common to each other.
_LA and the low altitude link step of sharing this generates a ^(k), the random number R _LA ^(k) from the second unmanned aircraft to encrypted communication with respect to the ground station, the random number R _LA ^(k) the transmitting and receiving information about the association of each other between the random number R _n ^(k) and the R _ST, each held between each ground station and the satellite, which has received the random number R _n ^(k) based on It is characterized by having a ground link step that generates a random number R common to each other and shares the random number R.

According to the present invention having the above-described configuration, in transmitting a radio signal transmitted from another aircraft via a plurality of unmanned aerial vehicles, a radio having directional transmission from another aircraft flying over the sky. A plurality of unmanned aerial vehicles approach each other to a range where the signal can be received, and after receiving the radio signal, deviate from the above range and fly away from each other.

As a result, even if the ground stations are dispersed, it is possible for the unmanned aerial vehicles to fly to individual ground stations by relaying multiple unmanned aerial vehicles between the satellite and the plurality of ground stations. It is possible to perform encrypted communication without omission. According to the present invention having the above-described configuration, since the random numbers held by the satellite and each ground station are generated based on the initial random numbers, it goes without saying that there are bits common to each other. Yes, it is a random number sequence that is highly related to each other. Therefore, it is possible to find bits common to each other and generate common random numbers to each other through simple transmission / reception of metadata. Therefore, the satellite and the ground station can perform encrypted communication with guaranteed information-theoretic security by creating and transmitting / receiving a one-time pad encryption using a common random number as an encryption key. In particular, since the initial random number can be generated infinitely on the satellite side via the initial random number generator, there is no possibility that the initial random number will be exhausted. Once a satellite is launched, it is almost impossible to replenish random numbers on the way, but according to the present invention, a common encryption key is used between the satellite and each ground station based on the initial random numbers generated from the satellite. It becomes possible to continuously generate new random numbers as. Further, according to the present invention, it is possible to continue the encrypted communication between each link based on the one-time pad encryption that can completely guarantee the information-theoretic security for the entire system by using the above-mentioned physical layer encryption. It becomes. Furthermore, the satellite can continue encrypted communication based on so-called one-to-many one-time pad encryption with a plurality of ground stations spread on the ground.

It is a figure which shows the whole structure of the encryption key sharing system to which this invention is applied. It is a figure which shows the system configuration of a satellite. It is a figure which shows the system configuration of a large aircraft. It is a figure which shows the system configuration of an unmanned aerial vehicle. It is a figure for demonstrating the processing operation method in a stratosphere link. It is a figure for demonstrating the processing operation method in a high altitude link. It is a figure for demonstrating the flight operation of each unmanned aerial vehicle of the first unmanned aerial vehicle layer in the case of shifting to a low altitude link. It is a figure for demonstrating the processing operation method in a low altitude link. It is a figure for demonstrating the flight operation of each unmanned aerial vehicle of the 2nd unmanned aerial vehicle layer in the case of shifting to a ground link. It is a figure for demonstrating the metadata generated in each ground station. It is a figure for demonstrating the example of transmitting the final metadata from each ground station to a satellite via a central base station. It is a figure which shows the example which transmits by broadcasting the final metadata from a satellite to all ground stations. It is a figure which shows the example which applies this invention to wireless cryptographic communication on the ground or near the ground.

Hereinafter, a mode for implementing the encryption key sharing system to which the present invention is applied will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of the encryption key sharing system 1 to which the present invention is applied. The encryption key sharing system 1 includes a satellite 2, a large aircraft 3 flying at a lower altitude than the satellite 2, an unmanned aerial vehicle layer 4 consisting of one or more layers flying at a lower altitude than the large aircraft 3, and a plurality of ground stations. 5 and a central base station 6 connected to each ground station 5. The purpose of this encryption key sharing system 1 is to share a common encryption key required for performing one-time pad encryption that can guarantee information-theoretic security between the satellite 2 and each ground station 5. There is.

Satellite 2 orbits a geostationary earth orbit (GEO) as an orbit around the earth with an orbital period that matches the rotation period of the earth, or is in an orbit located at a height of about 500 to 2000 km above the ground. It is an artificial satellite that orbits low earth orbit (LEO), etc., which rotates independently of the rotation period of. The satellite 2 may be launched based on any purpose. FIG. 2 shows the system configuration of the satellite 2. The satellite 2 includes an initial random number generation unit 21, a coding processing unit 22 connected to the initial random number generation unit 21, and a satellite communication unit 23 connected to the coding processing unit 22.

The initial random number generation unit 21 is a random number source that randomly generates a random number as an encryption key required for encrypted communication. The initial random number generated by the initial random number generation unit 21 is hereinafter referred to as a random number R ₀ . In the following description, the initial random number generation unit 21 will be _{described by taking the case of generating a random number R 0} as a physical random number string for an encryption key as an example, but the present invention is not limited to this, and is used for encryption. Any random number string for the encryption key may be used. The initial random number generation unit 21 outputs the generated random number R ₀ to the coding processing unit 22.

_{The coding processing unit 22 applies appropriate coding to the random number R 0} sent from the initial random number generation unit 21 in order to prevent error correction and leakage to an eavesdropper. _{That is, the coding processing unit 22 sets a random number R 0,} which is the base of the encryption key to be shared with the ground station 5, as plain text, performs appropriate encryption processing on the random number R 0, and sends the random number R 0 to the satellite communication unit 23. And send. The encryption processing performed by the coding processing unit 22 may be based on any conventional encryption method capable of ensuring information-theoretic security.

The satellite communication unit 23 converts the coded random number R ₀ sent from the coding processing unit 22 into a wireless signal by superimposing it on radio waves, laser light, or the like, and converts this into a large aircraft 3 flying in the stratosphere or troposphere. Send to. Further, the satellite communication unit 23 receives a radio signal composed of radio waves and laser light transmitted from the large aircraft 3 and the central base station 6.

The large aircraft 3 is a manned or unmanned aircraft such as a passenger aircraft, a transport aircraft, a military aircraft, and various observation aircraft. The large aircraft 3 is not limited to the case where it is actually large, but includes small aircraft, but it flies in the stratosphere or troposphere and is superimposed on radio waves or laser light with the satellite 2. Send and receive radio signals.

As shown in FIG. 3, the large aircraft 3 flies based on the flight control unit 30, and in addition to this, the satellite communication unit 31, the coding / decoding unit 32 connected to the satellite communication unit 31, and the coding / decoding. It includes a wireless communication unit 33 connected to the conversion unit 32, and further includes an arithmetic processing unit 34 connected to the coding / decoding unit 32. Further, a surveillance camera 35 connected to the flight control unit 30 and the arithmetic processing unit 34 is further provided.

The satellite communication unit 31 receives the radio signal sent from the satellite 2 and transmits it to the coding / decoding unit 32. The satellite communication unit 31 superimposes the signal transmitted from the coding / decoding unit 32 on the radio wave or the laser beam, and transmits the signal toward the satellite 2.

The coding / decoding unit 32 decodes the signals transmitted from the satellite communication unit 31 and the wireless communication unit 33, and then transmits the signals to the arithmetic processing unit 34. Further, the coding / decoding unit 32 performs appropriate coding / encryption processing on the random number sequence sent from the arithmetic processing unit 34 to prevent error correction and leakage to an eavesdropper, and wirelessly communicates the random number sequence. It is transmitted to the unit 33.

The arithmetic processing unit 34 decodes a signal such as a random number sequence from the coding / decoding unit 32 and performs various controls.

The wireless communication unit 33 converts a random number string from the coding / decoding unit 32 into a radio signal by superimposing it on radio waves, laser light, or the like, and transmits this to the unmanned aerial vehicle layer 4. The wireless communication unit 33 receives a radio signal composed of radio waves and laser light transmitted from the unmanned aerial vehicle layer 4.

The surveillance camera 35 confirms the field of view of the communication path by taking an image with the photographing direction directed to the communication path side. The image data captured by the surveillance camera 35 is sent to the flight control unit 30 and the arithmetic processing unit 34 and used for various determinations.

As shown in FIG. 1, the unmanned aerial vehicle layer 4 is assigned the first unmanned aerial vehicle layer 4-1 and the second unmanned aerial vehicle layer 4-2 in order from the highest altitude. However, the unmanned aerial vehicle layer 4 may be composed of at least one layer, or may be allocated over three or more layers. In the following example, the case where the unmanned aerial vehicle layer 4-1 and 4-2 are composed of two layers will be described as an example.

A plurality of unmanned aerial vehicles 40 will be arranged in each of the unmanned aerial vehicle layers 4-1 and 4-2. The unmanned aerial vehicle 40 referred to here is a so-called small aircraft capable of unmanned flight, and a typical one is a drone (multicopter), but it is not limited to this and is embodied by an unmanned helicopter or the like. It may be the one to be converted.

The unmanned aerial vehicle 40-1 assigned to the first unmanned aerial vehicle layer 4-1 located at the highest altitude transmits and receives various information to and from the large aircraft 3 flying at a higher altitude than itself. Further, the unmanned aerial vehicle 40-1 transmits and receives various information to and from the unmanned aerial vehicle 40-2 in the second unmanned aerial vehicle layer 4-2 flying at a lower altitude than itself. Further, the unmanned aerial vehicle 40-2 assigned to the second unmanned aerial vehicle layer 4-2 is connected to the unmanned aerial vehicle 40-1 in the first unmanned aerial vehicle layer 4-1 flying at a higher altitude than itself. Send and receive various information. Further, the unmanned aerial vehicle 40-2 transmits and receives various information to and from the ground station 5.

FIG. 4 shows a block configuration of a control unit 45 for controlling an unmanned aerial vehicle 40. The control unit 45 is supplied with power from the connected battery 44, is centered on the flight controller 50, and is connected to the coding / decoding unit 52, the wireless communication unit 51, and the ESC (Electronic Speed Controller), respectively. It is equipped with 54.

The unmanned aerial vehicle 40 can obtain buoyancy by rotating a plurality of rotors. This rotor can be rotated based on the rotation of the rotor motor 42. The rotor motor 42 can rotate based on the electric power supplied from the battery 44. The rotor can be rotated by rotating the rotor motor 42, and the unmanned aerial vehicle 40 can be immediately raised or lowered in the vertical direction, or can be stopped in place. When the unmanned aerial vehicle 40 is moved back and forth and left and right, the rotation speed of the rotor motor 42 in the traveling direction is decreased, and the rotation speed of the rotor motor 42 on the opposite side of the traveling direction is increased. As a result, the unmanned aerial vehicle 40 is in a leaning posture with respect to the traveling direction, and can move in the traveling direction. Further, by adjusting the output according to the rotation direction of the rotor motor 42, it is possible to rotate the unmanned aerial vehicle 40 itself. The rotation speed of these rotor motors 42 is controlled via the ESC 54 under the control of the flight controller 50 in the control unit 45.

The wireless communication unit 51 performs frequency conversion and other various conversion processes necessary for wireless communication with the large aircraft 3, other unmanned aerial vehicles 40, and ground stations, and converts the electric signal into radio waves. Alternatively, an antenna that converts radio waves into electrical signals is also included. The wireless communication unit 51 also includes a converter that converts a laser beam into an electric signal or a converter that converts an electric signal into a laser beam. The wireless communication unit 51 converts a signal superimposed on a radio wave or a laser beam transmitted from the outside into an electric signal and then outputs the signal to the coding / decoding unit 52. Further, the wireless communication unit 51 superimposes the signal transmitted from the coding / decoding unit 52 on the radio wave or the laser beam and transmits the signal to the outside.

The coding / decoding unit 52 decodes the signal transmitted from the wireless communication unit 51 and then transmits the signal to the flight controller 50. Further, the coding / decoding unit 52 performs appropriate coding / encryption processing on the random number sequence sent from the flight controller 50 to prevent error correction and leakage to an eavesdropper, and performs this on the wireless communication unit. Send to 51.

The flight controller 50 includes a control unit 57, a flight control sensor group 55 connected to the control unit 57, and a GPS receiving unit 56.

The control unit 57 is a so-called central calculation unit for controlling all the components. The control unit 57 notifies each component of an instruction for reading a program stored in a memory (not shown) and performing various operations. For example, if the program stored in the memory is related to the encryption processing method and the flight method in the unmanned aerial vehicle 40, the encryption processing is performed based on this, or various instructions for flying are stationary and each configuration is performed. Send to element.

The flight control sensor group 55 includes at least an accelerometer, an angular velocity sensor, a pressure sensor (altitude sensor), a geomagnetic sensor (orientation sensor), an altitude meter for detecting flight altitude, and a wind direction and wind speed meter for detecting wind speed and direction. It is composed of various sensors such as an acceleration sensor for detecting the tilt angle and tilt direction of the aircraft, a gyro sensor, and the like. The flight control sensor group 55 transmits each detected data to the control unit 57.

The GPS receiving unit 56 acquires the current position information of the unmanned aerial vehicle 40 during flight in real time based on the satellite positioning signal sent from the artificial satellite. The GPS receiving unit 56 transmits the acquired position information to the control unit 57.

Among the above-mentioned components, the flight controller 50, the ESC 54, and the like are all connected to the battery 44, and electric power is supplied.

The ground station 5 is a base station for wireless communication scattered on the ground. The ground station 5 is not limited to a base station that is completely fixed on the ground, but also includes a movable base station mounted on a vehicle or the like. The ground station 5 is configured to enable wireless communication with the unmanned aerial vehicle 40 in the second unmanned aerial vehicle layer 4-2. Further, the central base station 6 connected to each ground station 5 enables satellite communication with the satellite 2.

Next, a processing operation method of encryption key sharing by the encryption key sharing system 1 having the above-described configuration will be described. As shown in FIG. 1, the processing operation of the encryption key sharing is a stratospheric link between the satellite 2 and the large aircraft 3, and a high altitude performed between the large aircraft 3 and the first unmanned aerial vehicle layer 4-1. Link, low altitude link between first unmanned aerial vehicle layer 4-1 and second unmanned aerial vehicle layer 4-2, between second unmanned aerial vehicle layer 4-2 and ground station 5. It can be classified as a ground link.

In the stratospheric link, a _{common random number R ST} is generated with the large aircraft 3 based on the _{initial random number R 0} transmitted from the satellite 2, and in the high altitude link, it is based on _{the R ST transmitted from the large aircraft 3. A random number R HA} common to the first unmanned aerial vehicle layer 4-1 is generated. _{In the low altitude link, a random number R LA} common to the second unmanned aerial vehicle layer 4-2 is generated _{based on the R HA} transmitted from the first unmanned aerial vehicle layer 4-1. A common random number R is generated between each ground station 5 and the satellite 2 based on _{the R LA} transmitted from the second unmanned aerial vehicle layer 4-2. The random number R'that the ground station 5 initially acquires from the second unmanned aerial vehicle layer 4-2 is based on the initial random number R ₀ , but the generated random numbers R _ST , R _HA , R _LA , R'has a high proportion of being linked to each other. The ground station 5 transmits and receives metadata to and from the satellite 2 via the central base station 6, and creates a common random number R from the random _{numbers R ST and R', which are possessed by each and have a high ratio of being linked to each other.} Share this as an encryption key.

Hereinafter, the processing operation will be described in order from the stratosphere link. In the stratosphere link, first, as shown in FIG. 5, the large aircraft 3 evaluates the communication path characteristics of the communication path with the satellite 2. In this communication path characteristic evaluation, for example, the surveillance camera 35 of the large aircraft 3 is used to confirm the field of view of the communication path to the satellite 2, and no suspicious eavesdropping flying object or the like is flying between the satellite 2 and the satellite 2. Check. Further, in this communication path characteristic evaluation, the large aircraft 3 may transmit the probe signal toward the communication path, for example, via the satellite communication unit 31. The communication path characteristics may be estimated through this probe signal, and the characteristics may be evaluated by comparing with the evaluation data of the communication characteristics by the past probe signals.

Through such communication path characteristic evaluation, it was confirmed that there is no eavesdropping flying object between the large aircraft 3 and the satellite 2, or even if there is an eavesdropping flying object, it is considerably far from the communication path. Later, satellite 2 generates an _{initial random number R 0.} The initial random number R ₀ is generated by the initial random number generation unit 21, and after being sent to the coding processing unit 22, error correction or the like is performed. At this time, in this stratosphere link, the initial random number R ₀ as plain text may be encrypted by any conventional encryption technique capable of ensuring information-theoretic security. The encrypted initial random number R ₀ is transmitted to the large aircraft 3 via the satellite communication unit 23.

_{The data consisting of the ciphertext including the random number R 0} transmitted to the large aircraft 3 as plain text is received by the satellite communication unit 31 of the large aircraft 3 and decoded by the coding / decoding unit 32. Here, a random number obtained by receiving and decoding by the large aircraft 3 is defined as a random number R ₀ ′. The random number R ₀ 'is also be a completely identical with the initial random number R _0, may not necessarily the same depending on the environment of radio communication.

_{In the process of transmitting the initial random number R 0} in this stratosphere link, it may be encrypted by, for example, physical layer encryption. As the physical layer encryption, an appropriate one may be appropriately selected and used from the two methods of secret message transmission and private key exchange.

Confidential message transmission is a method of transmitting a message in one direction on one communication path. It is used when the communication path is relatively good, in other words, when it can be determined that the SN ratio of the large aircraft 3 as a regular receiver is superior to the SN ratio of the eavesdropper 83. In such a case, it can be assumed that the large aircraft 3 can receive the data of the initial random number R _{0 with a small error rate.}

When the confidential message transmission is adopted, the initial random number R ₀ is transmitted in one direction from the satellite 2 to the large aircraft 3. At this time, in order to perform more reliable transmission, the satellite 2 may _{prepare a plurality of copies of the initial random number R 0} and transmit these to the large aircraft 3 by interleaving. The coding / decoding unit 32 of the large aircraft 3 can obtain a plurality of random numbers after performing error correction. One of them is a random number R ₀ '.

Since the initial random number R ₀ and the random number R ₀ ´ may be different from each other, the satellite 2 and the large aircraft 3 are common to each other as shown in FIG. 5 in order to match them. The processing operation for obtaining the random number R _{ST is executed.}

In the secret message transmission, a _{common random number R ST} may be extracted by discarding bits that are different from each other between _{the initial random number R 0} and the random number R _{0', so-called residual error cutting.} .. The satellite 2 and the large aircraft 3 may negotiate with each other via a public communication channel. In such a case, the relationship between the data may be confirmed with each other, such as which bit position is common or different between the satellite 2 and the large aircraft 3. As an example of the negotiation between these satellites 2 and the large aircraft 3, what bit position is used, how many bits are averaged and how much error occurs, and so on. preoccupied to transmit and receive information only about sex, never random number R _0, R ₀ 'disclose or suggest without a public communication path, it is assumed that mutually check each other's association of only a fragment attribute information .. As a result, specific initial random numbers R ₀ and random numbers R ₀ ′ are not leaked to the outside only by transmitting and receiving such bit positions.

Through these confirmations, the arithmetic processing unit 34 in the large aircraft 3 finally determines the bit position to be left and the bit position to be discarded from the _{random number R 0 ′.} It is considered that the bit position to be left _{is common to the initial random number R 0,} and the bit position to be discarded is different from the _{initial random number R 0.} The large aircraft 3 notifies the satellite 2 of the bit position to be discarded via the public communication channel, and the satellite 2 discards the bit at the notified bit position. Similarly, the large aircraft 3 discards the bit at the bit position notified to the satellite 2 that it should be discarded. As a result, the satellite 2 and the large aircraft 3, so that the mutually leaving a random number R _ST as a common encryption key. In order to create a state in which the SN ratio of the large aircraft 3 as a regular receiver is superior to the SN ratio of the eavesdropper 83, the distance between the satellite 2 and the large aircraft 3 is measured or the communication distance is measured in advance. The signal strength of the satellite communication unit 23 of the satellite 2 may be adjusted so as to have a predetermined error rate in the satellite communication unit 31 of the large aircraft 3 for these distances.

By the way, when the communication path is relatively poor, the error rate of the received data in the large aircraft 3 is large, and in the above-mentioned confidential message transmission, there are too many bit positions different from each other under the poor communication environment, and the initial random number R _{A random number R ST} as an encryption key must be extracted by discarding a considerable number of bit positions from _0. As a result, the size of the random number R _ST as a common encryption key is much smaller than the initial random number R _0. In particular by the conditions of the communication path is sometimes no longer be shared random number R _ST as a common encryption key.

Therefore, if the communication path is relatively poor, and if it is judged that the SN ratio of the eavesdropper 83 is superior to the SN ratio of the large aircraft 3 of the regular receiver, the secret key exchange in the physical layer encryption is performed. conduct. In this private key exchange, in addition to the communication path for sharing random numbers, a public communication path for key distillation is prepared. An encryption key that ensures information-theoretic security is generated by appropriately combining a communication path that shares this random number and a public communication path for key distillation.

On the contrary, this method by exchanging the private key can be adopted even when the SN ratio of the eavesdropper 83 is inferior to the SN ratio of the large aircraft 3 of the regular receiver. However, in this secret key exchange method, it is necessary to prepare another public communication path in addition to the passage for sharing the random number as described above, so that power consumption and communication time are excessively consumed. Therefore, when selecting either method, the priority of confidential message transmission is set high, and the secret is given only when the SN ratio of the eavesdropper 83 is higher than the SN ratio of the large aircraft 3 of the regular receiver. It is desirable to select a key exchange method.

_{In this secret key exchange, the initial random number R 0} is regarded as a transmission message (plain text) from the satellite 2 side in the same manner as described above, and appropriate coding is applied to prevent error correction and leakage to eavesdroppers to the large aircraft 3. Send. _{The random number R 0} ′ acquired by the large aircraft 3 is further subjected to an appropriate key distillation process. As a result, even in this key distillation step, the random numbers R ₀ and R ₀ ′ are never disclosed or suggested on the public communication path, and only the information showing the fragmentary association is confirmed. Thus, the specific initial random number R0, numerical random number R ₀ 'without also leak outside, it is possible to generate a common random number R _ST from one another.

_{If the size of the random number R ST} of the common encryption key is significantly smaller than the size of the initial random number R ₀ as a result of adopting the above-mentioned physical layer encryption, in other words, the size (key length) L of the _{random number R ST. If ST} can only perform key distillation with a _{key length L 0} ′ shorter than that, a means for expanding the key _{to L ST} / L _{0 ′ times may be implemented by the method described below.} In this key expansion, a procedure of randomly shuffling from the _{initial random number R 0 to generate another random number Rs 1 , and further generating Rs 2} ... From the _{random number Rs 1} by the same processing. Then, the generated random numbers Rs ₁ to Rs _X may be sequentially connected and _{expanded to the required size L ST} to expand the key. In this case, instead of performing random shuffle, it may be performed L _ST / L ₀ 'times the key expansion by a simple calculation using the random number generated in situ.

Further, in this stratosphere link, the communication path characteristic evaluation result initially performed may be reflected in the parameters of the physical layer encryption. Examples of the parameters to be reflected include the redundancy of error correction, the code length, the message rate, the compression rate of the confidentiality enhancement, and the like.

The satellite 2 and the large aircraft 3 each hold _{a common random number R ST generated by the stratospheric link as described above.} The large aircraft 3 uses the generated random number R _ST to shift to the high altitude link described below.

When shifting to the high altitude link, as shown in FIG. 6, each of the plurality of unmanned aerial vehicles 40-1 in the first unmanned aerial vehicle layer 4-1 has a laser beam, a radio wave, or the like on which a random number sequence from the large aircraft 3 is superimposed. Signals approach each other to the extent that they can be broadcast. As shown in FIG. 6, this signal is premised on being transmitted in a state of having directivity in either direction. In such a case, the large aircraft 3 also descends to lower the altitude to the vicinity of the altitude at which each of these unmanned aerial vehicles 40-1 stands by. At this time, each unmanned aerial vehicle 40-1 may also be raised in altitude in order to get closer to the large aircraft 3.

At this time, if the radiation angle is wide, the laser beam or radio wave broadcast from the large aircraft 3 is likely to be captured by another eavesdropper 83's flying object. Therefore, by narrowing the beam of the laser beam broadcast from the large aircraft 3 as much as possible or narrowing the directivity of the radio wave as much as possible, a range consisting of a so-called secure zone in which the unmanned aerial vehicle 40-1 can receive a signal is formed. Even when the beam or the like actually broadcast from the large aircraft 3 is narrowed down, if the drone is used as the unmanned aerial vehicle 40-1, a plurality of unmanned aerial vehicles 40-1 can be set in a secure zone area having a diameter of, for example, about 10 m. Even in the case of, it is possible to fly while being almost stopped in a state of being close to each other.

Even in this high altitude link, the large aircraft 3 and / or the unmanned aerial vehicle 40-1 evaluates the communication path characteristics for the communication path. In this communication path characteristic evaluation, for example, the surveillance camera 35 in the large aircraft 3 and the flight control sensor group 55 of the unmanned aerial vehicle 40-1 are used to confirm the fields of view of each other's communication paths, and a suspicious eavesdropping flying object or the like is detected. Make sure you are not flying. Further, in the evaluation of the communication path characteristics in this high altitude link, the communication path characteristics may be evaluated via the probe signal.

Through such communication path characteristic evaluation, there is no eavesdropping aircraft between the large aircraft 3 and the plurality of unmanned aerial vehicles 40-1, or even if there is an eavesdropping aircraft, it is considerably far from the communication path. after confirming, large aircraft 3, the generated R _ST as plaintext, encodes it by the coding and decoding unit 32, encrypts a plurality of unmanned aircraft in the secure zone via the wireless communication unit 33 Broadcast to 40-1. This broadcast includes any concept as long as the signal is wirelessly transmitted from the wireless communication unit 33 to the plurality of unmanned aerial vehicles 40-1 in the secure zone. It should be noted that the present invention is not limited to the case where it is determined whether or not to transmit a random number according to the communication path characteristic evaluation result, and the step may be omitted.

Comprising data from the ciphertext that includes a plurality of unmanned aircraft 40-1 broadcast random number R _ST toward the plaintext, is received by the wireless communication unit 51 of each unmanned aircraft 40-1, decodes the encoding decoding portion 52 Be transformed. Here, the random number obtained by receiving and decoding by each unmanned aerial vehicle 40-1 is defined as a random number R _ST ⁽ⁿ⁾ . The random number R _ST ⁽ⁿ⁾ may be completely the same as the random number R _ST , but may not necessarily be the same depending on the wireless communication environment. Further, since the communication environment may be different between the plurality of unmanned aerial vehicles 40-1, the received random numbers R _ST ⁽ⁿ⁾ may be different from each other even between the unmanned aerial vehicles 40-1. Hereinafter, a random number k number of unmanned aircraft 40-1 receives each ^{_{R ST (1), R ST}} (2), R ST (3), ····, and R _ST ^(k).

_{In the process of transmitting the random number RST} in this high-altitude link, it may be encrypted based on any encryption method that can guarantee the information-theoretic security, but it may be encrypted by, for example, physical layer encryption. As the physical layer encryption, an appropriate one is appropriately selected from the two methods of secret message transmission and private key exchange based on the SN ratio of the unmanned aerial vehicle 40-1 of the regular recipient and the SN ratio of the eavesdropper 83. You may use it.

In the confidential message transmission, it is used when it can be determined that the SN ratio of the unmanned aerial vehicle 40-1 as a regular receiver is higher than the SN ratio of the eavesdropper 83.

_{When the confidential message transmission is adopted, the random number RST} is transmitted in one direction from the large aircraft 3 to the unmanned aerial vehicle 40-1. Large aircraft 3 this time, for more secure transmission, a copy of the random number R _ST preparing a plurality may be transmitted toward the unmanned aircraft 40-1 these by interleaving. In the coding / decoding unit 52 of the unmanned aerial vehicle 40-1, after performing error correction, the random numbers R _ST ⁽¹⁾ , R _ST ⁽²⁾ , R _ST ⁽³⁾ , ..., R _ST ^{(k), respectively. )} Can be obtained.

Random numbers R _ST and random numbers R _ST ⁽¹⁾ , R _ST ⁽²⁾ , R _ST ⁽³⁾ , ..., R _ST ^(k) are different from each other, although they have some relation to each other. Since there is a possibility, in order to match with these, the large aircraft 3 and each unmanned aerial vehicle 40-1 execute a processing operation for obtaining _{a random number R HA common to each other as shown in FIG.} do.

This confidential message transmission, after restoring multiple copies of interleaved random number R _ST, performs Reaper residual error, to extract the random number data. However, due to the difference in communication path characteristics between the plurality of unmanned aerial vehicles 40-1, the random number data that can be actually acquired by each unmanned aerial vehicle 40-1 are random numbers R _ST ⁽¹⁾ , R _ST ⁽²⁾ , and R. _ST ⁽³⁾ , ..., R _ST ^(k) . The large aircraft 3 and each unmanned aerial vehicle 40-1 confirmed the relationship between _{the random number R ST} and the random numbers R _ST ⁽¹⁾ , R _ST ⁽²⁾ , ..., R _ST ^(k). By meeting, negotiations are performed to obtain a subset R _{HA of common random numbers.} This negotiation is performed via the transmission and reception _{of metadata D HA on the public channel.} The metadata D _HA to be sent and received should contain only information about the relationship between data, such as what bit position to use and how many bits should be averaged to make an error. Therefore, the _{random numbers R ST and R ST} ⁽ⁿ⁾ are never disclosed or suggested on the open communication path, and only the information on the fragmentary association is confirmed. As a result, the specific random numbers R _ST and R _ST ⁽ⁿ⁾ are not leaked to the outside.

In the large aircraft 3, the random numbers R _{ST and the random numbers R ST} ⁽¹⁾ , R _ST ⁽²⁾ , in all the unmanned aerial vehicles 40-1 are _{based on the metadata D HA} sent from each of these unmanned aerial vehicles 40-1. Determine the bit positions common to each other with R _ST ⁽³⁾ , ..., R _ST ^(k). _{Then, a metadata D HA} that newly incorporates the information regarding the determined bit position is generated, and this is transmitted to each unmanned aerial vehicle 40-1. Each unmanned aerial vehicle 40-1 that has received this metadata D _HA discards bits based on the information of the bit position (remaining bit position) common to each other or the bit position to be discarded described in the _{metadata D HA.} I do. Similarly, the large aircraft 3 leaves the bits at the bit positions common to each other and discards the bits at the other bit positions. _{As a result, random number data R HA} as an encryption key common to each other is generated between the large aircraft 3 and all the unmanned aerial vehicles 40-1.

In order to create a state in which the SN ratio of the unmanned aerial vehicle 40-1 as a regular receiver is superior to the SN ratio of the eavesdropper 83, the distance between the large aircraft 3 and the unmanned aerial vehicle 40-1 is measured. Alternatively, the communication distances are specified in advance, and the signal strength of the radio communication unit 33 of the large aircraft 3 is adjusted so that the error rate is determined in advance by the radio communication unit 51 of the unmanned aerial vehicle 40-1 for these distances. May be good.

Further, even in this high altitude link, when the communication path is relatively poor, the SN ratio of the eavesdropper 83 is judged to be superior to the SN ratio of the unmanned aerial vehicle 40-1 of the regular receiver. , Performs private key exchange in physical layer encryption. In this secret key exchange is regarded as a large aircraft 3 transmits the random number R _ST in the same manner as described above from the side message (plain text), unmanned aerial vehicle is subjected to appropriate encoding in order to prevent leakage of the error correction and eavesdroppers 40- Send to 1. Each unmanned aerial vehicle 40-1 performs a key distillation process on _{the acquired random numbers R ST} ⁽¹⁾ , R _ST ⁽²⁾ , ..., R _ST ^(k). As a result, even in this key distillation step, the random numbers R _ST and R _ST ⁽ⁿ⁾ are never disclosed or suggested on the public communication path, and only fragmentary attribute information is confirmed via the _{metadata D HA.} It shall fit. As a result, it is possible to generate _{random numbers R HA} common to each other without leaking _{specific random numbers R ST} and R _ST ^{(n) to} the outside only by transmitting and receiving such bit positions.

In the description of the physical layer encryption in this high altitude link, it goes without saying that the method described in the stratosphere link may be applied to any of the other processing operation methods.

The large aircraft 3 and each unmanned aerial vehicle 40-1 each hold _{a common random number R HA generated by the high altitude link as described above.} The unmanned aerial vehicle 40-1 uses the generated random number _RHA to shift to the low altitude link described below.

When shifting to the low altitude link, as shown in FIG. 7, each of the plurality of unmanned aerial vehicles 40-1 in the first unmanned aerial vehicle layer 4-1 deviates from the range of the secure zone set in the high altitude link, respectively. It descends to the flight altitude of the second unmanned aerial vehicle layer 4-2, separated from each other. Instead, the unmanned aerial vehicle 40-2 in the second unmanned aerial vehicle layer 4-2 may be made to rise to the flight altitude of the first unmanned aerial vehicle layer 4-1. Further, the unmanned aerial vehicle 40-1 may descend and the unmanned aerial vehicle 40-2 may ascend.

The plurality of unmanned aerial vehicles 40-1 descend separately in each airspace at low altitude. It is assumed that a plurality of unmanned aerial vehicles 40-2 are flying in each airspace in the second unmanned aerial vehicle layer 4-2 at a low altitude. It is assumed that a plurality of unmanned aerial vehicles 40-2 are pre-assigned to each unmanned aerial vehicle 40-1 that has descended to each airspace. The plurality of unmanned aerial vehicles 40-2 in each airspace approach each other to a range in which signals such as laser light and radio waves on which a random number sequence from the unmanned aerial vehicle 40-1 is superimposed can be broadcast.

The laser beam and radio waves broadcast from the unmanned aerial vehicle 40-1 form a secure zone by further narrowing the radiation angle, and the plurality of unmanned aerial vehicles 40-2 are mutually formed in the secure zone region formed in this narrow region. Fly while staying in close proximity. The broadcast described above includes any concept as long as it wirelessly transmits a signal to a plurality of unmanned aerial vehicles 40-2 in a secure zone. As shown in FIG. 8, it is premised that the wirelessly transmitted signal is transmitted in a state of having directivity in either direction.

Even in this low altitude link, the unmanned aerial vehicle 40-1 and / or the unmanned aerial vehicle 40-2 evaluates the communication path characteristics for the communication path as shown in FIG. This communication path characteristic evaluation method is the same as that for high altitude links.

Through a communication channel characterization, after confirming such that there is no eavesdropping aircraft between unmanned aircraft 40-1 and a plurality of unmanned aircraft 40-2, unmanned aircraft 40-1, the generated R _HA as plaintext, which Is encoded and encrypted by the coding / decoding unit 52, and is broadcast to a plurality of unmanned aerial vehicles 40-2 in the secure zone via the wireless communication unit 51.

_{The data consisting of the ciphertext including the random number R HA} broadcasted to the plurality of unmanned aerial vehicles 40-2 as plain text is received by the radio communication unit 51 in each unmanned aerial vehicle 40-2 and decoded by the coding / decoding unit 52. Be transformed. Here, the random number obtained by receiving and decoding by each unmanned aerial vehicle 40-2 is _defined ^{as a random number R HAk (n)} . The random number R _HAk ⁽ⁿ⁾ may be completely the same as the random number R _HA , but may not necessarily be the same depending on the wireless communication environment. Further, since the communication environment may be different between the plurality of unmanned aerial vehicles 40-2, the received random numbers R _HAk ⁽ⁿ⁾ may be different from each other even between the unmanned aerial vehicles 40-2. Hereinafter, the random numbers received by the k unmanned aerial vehicles 40-2 are referred to as R _HAk ⁽¹⁾ , R _HAk ⁽²⁾ , ..., R _HAk ^(k) , respectively.

_{In the process of transmitting the random number R HA} on this low altitude link, any cryptographic communication method that can ensure information-theoretic security may be applied, and for example, it may be encrypted by physical layer encryption. As the physical layer encryption, an appropriate one is appropriately selected from the two methods of secret message transmission and secret key exchange based on the SN ratio of the unmanned aerial vehicle 40-2 of the regular recipient and the SN ratio of the eavesdropper 83. You may use it. The specific method of secret message transmission and private key exchange is the same as that of the high altitude link, so the explanation is omitted. However, in either method, the random number R _HA transmitted from the unmanned aerial vehicle 40-1 and each unmanned aerial vehicle 40 It is possible that the random numbers R _HAk ⁽¹⁾ , R _HAk ⁽²⁾ , R _HAk ⁽³⁾ , ..., R _HAk ^(k) received by -2 are related to each other but different from each other. Therefore, in order to match with these, the unmanned aerial vehicle 40-1 and each unmanned aerial vehicle 40-2 are processed to obtain _{a random number R LA} ^{(k) common to each other as shown in FIG.} To execute. This processing operation confirms the linkage with each other in order to obtain _{a subset of random numbers R LA} ^(k) common to each other between the unmanned aerial vehicle 40-1 and each unmanned aerial vehicle 40-2 as in the case of the high altitude link. Negotiate. This negotiation may be performed via the transmission / reception of metadata D _{LAk on the public channel.} The metadata D _LAk to be sent and received is made public by including only information on the association, such as what bit position is used and how many bits are averaged to make an error. _{Random numbers R HA} and R _HAk ⁽ⁿ⁾ shall never be disclosed or suggested on the communication path, and shall be confirmed only by information on fragmentary associations. As a result, _{the numerical values of specific random numbers R HA} and R _HAk ⁽ⁿ⁾ are not leaked to the outside.

Since the unmanned aerial vehicle 40-1 is negotiating with all the unmanned aerial vehicles 40-2 under its control or _{receiving the metadata D LAk} , it is possible to grasp the relationship between the random numbers of each other. Because it is made, between the random number R _{HA and the random numbers R HAk} ⁽¹⁾ , R _HAk ⁽²⁾ , R _HAk ⁽³⁾ , ..., R _HAk ^(k) in all unmanned aerial vehicles 40-2. Bit positions common to each other can be determined. _{Then, a metadata D HAk} ^(k) newly incorporating the information regarding the determined bit position is generated, and this is transmitted to each unmanned aerial vehicle 40-2. Each unmanned aircraft 40-2 which has received the metadata D _HAk ^(k) is a common bit position to each other is described in the meta data D _HAk ^(k) (left bit position), or information of bit positions to be discarded Based on, discard the bit. Similarly, the unmanned aerial vehicle 40-1 leaves bits at bit positions common to each other and discards bits at other bit positions. _{As a result, random number data R LA} ^(k) as an encryption key common to each other is generated between the unmanned aerial vehicle 40-1 and all the unmanned aerial vehicles 40-2.

In order to create a state in which the SN ratio of the unmanned aerial vehicle 40-2 as a regular receiver is superior to the SN ratio of the eavesdropper 83, the distance between the unmanned aerial vehicle 40-1 and the unmanned aerial vehicle 40-2 is measured. Alternatively, the communication distances are specified in advance, and the signal strength of the radio communication unit 51 of the unmanned aerial vehicle 40-1 is adjusted so that the error rate is determined in advance by the radio communication unit 51 of the unmanned aerial vehicle 40-2 for these distances. You may try to do it.

Further, even in this low altitude link, when the communication path is relatively poor, the SN ratio of the eavesdropper 83 is judged to be superior to the SN ratio of the unmanned aerial vehicle 40-2 of the regular receiver. , Performs private key exchange in physical layer encryption. The specific method of this private key exchange is the same as that of the high altitude link.

In the explanation of the physical layer encryption in this low altitude link, it goes without saying that the method described in the stratosphere link and the high altitude may be applied to any of the other processing operation methods.

By executing the above-mentioned processing between the unmanned aerial vehicle 40-1 and the plurality of unmanned aerial vehicles 40-2 for each airspace, random data as an encryption key common to each other in the unmanned aerial vehicles 40-2 in the individual airspaces. R _LA ^(k) is generated.

The unmanned aerial vehicle 40-1 and the plurality of unmanned aerial vehicles 40-2 each hold _{a common random number R LA} ^{(k) generated by the low altitude link as described above.} Each unmanned aerial vehicle 40-2 uses the generated random number R _LA ^(k) to shift to the ground link described below.

When migrating to the ground link, as shown in FIG. 9, each of the plurality of unmanned aerial vehicles 40-2 in the second unmanned aerial vehicle layer 4-2 deviates from the range of the secure zone set in the low altitude link and deviates from each other. It descends to the flight altitude of the ground station 5 at a distance. Each unmanned aerial vehicle 40-2 is assigned a ground station 5 under its jurisdiction. Therefore, the plurality of unmanned aerial vehicles 40-2 that were close to each other on the low altitude link will be separated from each other and will fly to the ground station 5 under their respective jurisdiction. It should be noted that the present invention is not limited to the case where one ground station 5 is assigned to one unmanned aerial vehicle 40-2, and a plurality of ground stations 5 are assigned to one unmanned aerial vehicle 40-2. It may be a thing.

Each unmanned aerial vehicle 40-2 approaches each other to a range in which signals such as laser light and radio waves on which a random number sequence is superimposed can be broadcast.

Also in this ground link, the unmanned aerial vehicle 40-2 and / or the ground station 5 evaluates the communication path characteristics of the communication path. This communication path characteristic evaluation method is the same as that for high altitude links and low altitude links. Incidentally, the communication path characteristic evaluation may be omitted in this ground link.

After confirming that there is no eavesdropping aircraft between the unmanned aerial vehicle 40-2 and the ground station 5 through the communication path characteristic evaluation, the unmanned aerial vehicle 40-2 uses the generated R _LA ^(k) as plain text. It is encoded and encrypted by the coding / decoding unit 52, and broadcast to the ground station 5 via the wireless communication unit 51. This broadcast includes any concept as long as it wirelessly transmits a signal to the ground station 5. child

_{The data consisting of the ciphertext containing the random number R LA} ^(k) broadcasted to the plurality of unmanned aerial vehicles 40-2 as plain text is received by the ground station 5 and decrypted. _{In the process of transmitting the random number R LA} ^(k) on this ground link, it may be encrypted by, for example, physical layer encryption. As the physical layer encryption, an appropriate one is appropriately selected from the two methods of secret message transmission and private key exchange based on the SN ratio of the ground station 5 which is a regular receiver and the SN ratio of the eavesdropper 83. You may choose to use it. Since the specific methods of secret message transmission and private key exchange are the same as those of high-altitude links and low-altitude links, the description thereof will be omitted.

Here, a random number obtained by receiving and decoding by each ground station 5 is _{defined as a random number R n} ^(k) . ^{The superscript (k)} in this random number R _n (k) is a number corresponding to each airspace of the unmanned aerial vehicle 40-2. Further, n in the subscript is a number assigned to each ground station 5. When there are i ground stations 5 in each of the k airspaces, the random numbers R _n ^(k) are R ₁ ⁽¹⁾ , ..., R _i ^{(1), respectively, as shown in FIG.} , R ₁ ⁽²⁾ , ..., R _i ⁽²⁾ , R ₁ ^(k) , ..., R _i ^(k) . The random number R _n ^(k) may be completely the same as the random number R _LA ^(k) , but may not necessarily be the same depending on the wireless communication environment. Further, since the communication environment may be different between the ground stations 5, the received random numbers R _n ^(k) may be different between the ground stations 5. However, these R ₁ ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , ..., R _i ⁽²⁾ , R ₁ ^(k) , ..., R _i ^(k) are to the last. Although it is based on the random number R _LA ^(k) , it is related to each other at least to some extent, and is also related to the random number R _LA ^(k) .

Each ground station 5 generates metadata as shown in FIG. In each ground station 5, the metadata corresponding to _{R 1} ⁽¹⁾ _{is D 1} ⁽¹⁾ , the metadata corresponding to _{R 2} ⁽¹⁾ _{is D 2} ^(1), and the metadata corresponding to _{R i} ^{(1) is} _{Let the} data be D _i ⁽¹⁾ and the metadata corresponding to ^{R n (k)} _{be D n} ^(k) . The ground station 5 has generated each metadata D ₁ ⁽¹⁾ , ..., _Di ⁽¹⁾ , D ₁ ⁽²⁾ , ..., _Di ⁽²⁾ , D ₁ ^{(k) as shown in FIG. )} , ..., _Di ^(k) is transmitted to the central base station 6. Similarly, these metadata D _n ^(k) are also made public by including only information such as which bit position is used and how many bits are averaged to cause an error. _{Random numbers R n} ^(k) are never disclosed or suggested on the communication path, and are confirmed only by fragmentary attribute information. Similarly, the central base station 6 also transmits metadata to each ground station 5 to mutually confirm the bit positions common to each other. Since the central base station 6 _{can receive the metadata D n} ^(k) from all the ground stations, it can grasp the positions of bits common to each other and the positions of bits different from each other among all the ground stations 5. can do.

As shown in FIG. 11, the central base station 6 creates the final metadata D _{final based on the metadata D n} ^(k) collected from all of these ground stations 5, and directs it toward the satellite 2. Send. This final metadata D _final reflects information on the bit positions common to all ground stations 5, but as the specific data content, the bit position is used as described above. By including only information on the relationship between each other, such as how many bits are averaged and how much error occurs, the random number R _n ^(k) is never disclosed or disclosed on the open communication path. Don't suggest.

The satellite 2 receives such final metadata D _final via the satellite communication unit 23 and collates it with the _{random number data RST owned by the satellite 2.} The final metadata D _{final is the random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , ..., R _i ⁽²⁾ , R ₁ ^(k) acquired by each ground station 5. , ..., The bit position of the bit common to _Ri ^{(k) is reflected.} Therefore, by acquiring this final metadata D _final , the satellite 2 acquires the random number data R _{ST and the random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽² ) acquired by each ground station 5. ⁾ , ..., R _i ⁽²⁾ , R ₁ ^(k) , ..., It is possible to confirm the bit position of the bits common to _{R i} ^{(k), and by extension, the mutual relationship.} Can be confirmed.

Finally, the satellite 2 generates the _{metadata D final} ′ to be transmitted to the ground station 5. This metadata D _{final'is the random numbers R 1} ⁽¹⁾ , ..., _Ri ⁽¹⁾ , R ₁ ⁽²⁾ , ..., _Ri ⁽²⁾ , R acquired by R _ST and each ground station 5. Information on the bit position of the bits common to ₁ ^(k) , ..., _Ri ^{(k) is reflected.} Similar to the above, this metadata D _final ´ also contains only information on the relationship such as which bit position is used, how many bits are averaged and how much error occurs. Of course. The satellite 2 newly generates a random number R from _{the random number R ST} based on the contents included in the generated metadata D _{final ′. Further, the satellite 2 transmits the metadata D final} ′ to all the ground stations 5 via the satellite communication unit 23 by broadcasting as shown in FIG.

All the ground stations 5 _{receive the metadata D final} ′ broadcast from the satellite 2 and newly generate a random number R based on the metadata D final ′. The metadata D _final ´ is _{the random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , ..., R _i ⁽²⁾ , R _{1 acquired by R ST} and each ground station 5. ^{Since the information on the bit position of the bit common to (k)} , ..., _Ri ^(k) is reflected, based on this, the satellite 2 and all the ground stations 5 are connected. It is possible to match random numbers R as encryption keys common to each other. In particular, the generation of this random number R can be realized only by leaving only the bits common to _{R ST} and _Ri ^{(k) and deleting the bits different from each other.} By performing the process of leaving only the common bit, the above-mentioned common random number R is created. As a result, the satellite 2 and each ground station 5 will eventually share the random number data R that is common to each other. _{Random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , ..., R _{i acquired by R ST} and each ground station 5 through the transmission and reception of metadata D _final and D _{final ´. ^{(2), R 1 (k}} ), ··, if it can be confirmed each other relevancy between R _i ^(k), may be used in any other way.

In particular, since these R _ST and R _i ^(k) are originally generated based on the initial random number R ₀ , they are related to each other, and it goes without saying that there are common bits, and they are related to each other. It is a highly probable random number sequence. Therefore, it is highly possible that bits common to each other can be found through simple transmission and reception of metadata.

Therefore, the satellite 2 and each ground station 5 can perform encrypted communication with guaranteed information-theoretic security by creating and transmitting / receiving a one-time pad encryption using the random number R as an encryption key. _{In particular, since the initial random number R 0} can be generated infinitely on the satellite 2 side via the initial random number generation unit 21, there is no possibility that the initial random number R 0 will be exhausted. Once the satellite 2 is launched, it is almost impossible to replenish random numbers on the way, but according to the present invention, between the satellite 2 and each ground station 5 based on the _{initial random number R 0 generated from the satellite 2.} It becomes possible to continuously create a new random number R as an encryption key common to each other. Further, according to the present invention, it is possible to continue the encrypted communication between each link based on the one-time pad encryption that can completely guarantee the information-theoretic security for the entire system by using the above-mentioned physical layer encryption. It becomes. Further, the satellite 2 can continue the encrypted communication based on the so-called one-to-many one-time pad encryption with the plurality of ground stations 5 spread on the ground.

As a method of enhancing the information-theoretic security in actual operation, the finally shared random number data R is appropriately divided to prepare R'and R', and Fisher-Yates is used using the random number R'. R ″ may be a random numbered R ″ called shuffle, and this may be used as an encryption key.

An object of the present invention is to generate and share a common random number R between the satellite 2 and the ground station 5, but the present invention is not limited to this. A common random number R may be generated between the large aircraft 3 and the ground station 5 and shared with each other.

In such a case, the configuration of the satellite 2 and the stratosphere link are omitted in the encryption key sharing system 1, and _{instead of generating the initial random number R 0 on the satellite 2 side, the initial random number R ST} is generated on the large aircraft 3. _{After that, the random number R HA} is acquired in the large aircraft 3 by similarly executing the processing operation on the high altitude link. The low altitude link and the ground link are the same as above, but the central base station 6 creates the final metadata D _{final based on the metadata D n} ^{(k) collected from all the ground stations 5.} This is transmitted to the large aircraft 3.

The large aircraft 3 receives the final metadata D _final via the wireless communication unit 33 and collates it with the _{random number data R HA that it owns. By acquiring the final metadata D final} , the large aircraft 3 has random number data R _{HA and random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , acquired by each ground station 5. It is possible to confirm the bit position of the bit common to R _i ⁽²⁾ , R ₁ ^(k) , ..., R _i ^(k).

The large aircraft 3 finally generates _{metadata D final} ′ to be transmitted to the ground station 5. This metadata D _{final'is the random numbers R 1} ⁽¹⁾ , ..., R _i ⁽¹⁾ , R ₁ ⁽²⁾ , ..., R _i ⁽²⁾ , R acquired by R _HA and each ground station 5. Information on the bit position of the bits common to ₁ ^(k) , ..., _Ri ^{(k) is reflected.} The large aircraft 3 newly generates a random number R from _{the random number R HA} based on the contents included in the generated metadata D _{final ´.} Further, the large aircraft 3 transmits the _{metadata D final} ′ to all the ground stations 5 via the wireless communication unit 33.

All ground stations 5 receive the _{metadata D final} ′ transmitted from the large aircraft 3. Then, as described above, it is possible to share the random number R as an encryption key common to each other with the large aircraft and all the ground stations 5.

Further, in the above-described embodiment, the case where the unmanned aerial vehicle layer 4 is composed of two layers, the first unmanned aerial vehicle layer 4-1 and the second unmanned aerial vehicle layer 4-2, has been described as an example. , Not limited to this. The relay unmanned aerial vehicle layer 4 may be inserted over one or more layers between the first unmanned aerial vehicle layer 4-1 and the second unmanned aerial vehicle layer 4-2. The processing operation method of the unmanned aerial vehicle layer 4 for relay is the same as the low altitude link described above.

Further, according to the present invention, the unmanned aerial vehicle layer 4 may be composed of one layer of the first unmanned aerial vehicle layer 4. In such a case, the unmanned aerial vehicle 40-1 in the first unmanned aerial vehicle layer 4 descends to just above the ground station 5 after terminating the high altitude link, and performs the processing operation on the ground link with the second unmanned aerial vehicle. The unmanned aerial vehicle 40-1 will take the place of 40-2.

Further, according to the present invention, it is embodied as a signal transmission system by an unmanned aerial vehicle for transmitting a radio signal transmitted from another aircraft via a plurality of unmanned aerial vehicles 40 on a high altitude link or a low altitude link. It may be a thing.

In the high altitude link, a plurality of unmanned aerial vehicles 40-1 are brought close to each other within the range of the secure zone in which the directional radio signal transmitted from the large aircraft 3 flying over the sky can be received. Then, the unmanned aerial vehicle 40-1 that has received the radio signal from the large aircraft 3 in the secure zone transmits the radio signal by departing from the range of the secure zone and flying away from each other.

Similarly, at low altitude links, multiple unmanned aerial vehicles 40-2 are brought close to each other to the extent of a secure zone in which directional radio signals transmitted from unmanned aerial vehicle 40-1 flying over can be received. Then, the unmanned aerial vehicle 40-2, which has received the radio signal from the unmanned aerial vehicle 40-1 in the secure zone, deviates from the range of the secure zone and flies away from each other to transmit the radio signal.

That is, both the high-altitude link and the low-altitude link are secure capable of receiving directional radio signals transmitted from other airplanes (unmanned aerial vehicle 40, large aircraft 3) flying over the unmanned aerial vehicle 40. It may be embodied in any form as long as it is close to each other up to the range of the zone.

At this time, the transmitted radio signal is not limited to the above-mentioned random numbers, and may be any. Further, the transmitted radio signal is not limited to the case where it is encrypted, and includes an unencrypted state.

It goes without saying that ordinary radio signals can be transmitted by realizing the operation of the unmanned aerial vehicle 40 as described above. Further, even in the high altitude link and the low altitude link of the encryption key sharing system 1 to which the present invention is applied, the unmanned aerial vehicle 40 is flown to the secure zone narrowed down by giving directivity to the beam and radio waves to perform wireless communication. It can be safely transmitted without being intercepted by other unmanned aerial vehicles.

Further, the present invention can be similarly applied to wireless encrypted communication on the ground or near the ground as shown in FIG. Central control station 103 in other equipment city installed on the ground plays a role as the satellite 2 to generate an initial random number R _ST, which toward the moving body layer 104 consisting of one or more layers to encrypted communication. The moving body 141 in the moving body layer 104 that has received the random number R _ST ^(k) based on the initial random number R _ST may be the above-mentioned unmanned aerial vehicle 40, a vehicle traveling on the ground, or moving on the sea. It is a concept that includes any mobile object, including ships and even humans.

The mobile body 141 generates _{a random number R HA} common to each other by transmitting and receiving information on the mutual relationship between the _{initial random number R ST} and the random number R _ST ^(k) with the central control station. Share.

The mobile layer 104 encrypts and communicates a _{random number R LA} ^(k) based on the random _{number R HA} with the terminal mobile body 105 by relaying the _{random number R HA in the same manner as described above.} The terminal mobile body 105 is also a concept including any movable object like the mobile body 141.

The terminal mobile 105 receives a random _{number R n} ^(k) based on the random _{number R LA} ^(k) . Then, similarly to the satellite 2 and the ground station 5 described above, the terminal mobile body 105 and the central control station 103 transmit and receive information on the mutual relationship between the _{random numbers R n} ^(k) and R _{HA held by each.} conduct. Information on this association may be transmitted and received to _{and from the metadata D final} and D _final ′ as in the case of the satellite 2 and the ground station 5. As a result, random numbers R common to each other can be generated and shared.

1 Encryption key sharing system 2 Satellite 3 Large aircraft 4 Unmanned aerial vehicle layer 5 Ground station 6 Central base station 21 Initial random number generation unit 22 Coding processing unit 23 Satellite communication unit 30 Flight control unit 31 Satellite communication unit 32 Coding and decoding unit 33 Wireless communication unit 34 Arithmetic processing unit 35 Surveillance camera 40 Unmanned aerial vehicle 42 Rotor motor 44 Battery 45 Control unit 50 Flight controller 51 Wireless communication unit 52 Coding and decoding unit 54 ESC
55 Flight control sensor group 56 GPS receiver 57 Control unit 83 Eavesdropper

Claims (4)

In a signal transmission system including a plurality of unmanned aerial vehicles that relays directional radio signals transmitted from a large aircraft to a ground station.
Each of the plurality of unmanned aerial vehicles moves to a range in which the radio signal can be received, approaches each other, deviates from the range after receiving the radio signal, and transmits the radio signal to the ground station. An unmanned aerial vehicle signal transmission system characterized by relaying. A satellite, a large aircraft flying at a lower altitude than the satellite, an unmanned aerial vehicle layer having one or more layers including a plurality of unmanned aerial vehicles flying at a lower altitude than the large aircraft, and a plurality of ground stations. With
The satellite generates an initial random number R0 for an encryption key, performs cryptographic communication with the large aircraft, and receives a random number R0'based on the initial random number R0 between the large aircraft and the satellite. By transmitting and receiving information on the mutual relationship between the initial random number R0 and the above random number R0', a random number RST common to each other is generated and shared.
By relaying the unmanned aerial vehicle layer from the large aircraft, the random number RLA (k) based on the random number RST is encrypted and communicated with the ground station.
Transmission and reception of information on the mutual relationship between the random number Rn (k) and the RST held by each ground station and the satellite that received the random number Rn (k) based on the random number RLA (k). The signal transmission system by an unmanned aerial vehicle according to claim 1, wherein a random number R common to each other is generated and shared by the above. It is provided with the above-mentioned large aircraft, one or more layers of unmanned aerial vehicles including the above-mentioned unmanned aerial vehicles flying at a lower altitude than the above-mentioned large aircraft, and the plurality of the above-mentioned ground stations.
A plurality of random numbers RST (k) based on the initial random number RST are generated by generating an initial random number RST for an encryption key by the large aircraft, performing cryptographic communication with the unmanned aircraft layer composed of one or more layers, and receiving the random number RST (k) based on the initial random number RST. By transmitting and receiving information on the mutual relationship between the initial random number RST and the random number RST (k) between the unmanned aircraft and the large aircraft, a random number RHA common to each other is generated and shared.
By relaying the unmanned aerial vehicle layer, the random number RLA (k) based on the random number RHA is encrypted and communicated with the ground station.
Information on the mutual relationship between the random number Rn (k) and the random number RHA held by each ground station receiving the random number Rn (k) based on the random number RLA (k) and the large aircraft. The signal transmission system by an unmanned aerial vehicle according to claim 1, wherein a random number R common to each other is generated and shared by transmitting and receiving. The large aircraft or the unmanned aerial vehicle in the unmanned aerial vehicle layer evaluates the communication characteristics in the communication path before transmitting the random numbers, and determines whether or not to transmit the random numbers based on the evaluation result of the communication characteristics. The signal transmission system by an unmanned aerial vehicle according to claim 2 or 3, wherein the signal transmission system is characterized.

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