JP7486168B2 - System and method for securely sharing encryption keys between two points via flying object - Google Patents

Description

The present invention relates to an encryption key sharing system and method that enables secure sharing of an encryption key between two points on the ground without leaving any key information on the flying object.

Traditionally, there has been a demand for reliable communication technology between multiple base stations that are far apart. One such highly reliable technology is quantum key distribution. Quantum key distribution is a technology that uses the quantum mechanical properties of light to share encryption keys between multiple base stations. As an example, there is a case where encryption keys were successfully distributed between multiple base stations that were separated by 12,000 km.

Quantum key distribution technology between multiple base stations via satellites is also known. Non-Patent Document 1 discloses a technology in which encryption keys are distributed between multiple base stations via satellites. Specifically, as is also used in terrestrial quantum key distribution networks, keys are relayed assuming a trusted node. In the case of satellite quantum cryptography, it is expected that satellites will also become trusted nodes. Trusted terrestrial nodes can be quickly restored even if they are contaminated by a cyber attack, but in the case of satellites, human verification is extremely difficult.

Patent Document 1 also discloses a secret key sharing system in which an authorized receiver device and a sender device generate encryption keys for optical space communication and RF band communication and distribute them to the authorized receiver device via optical space communication and RF band communication, share the encryption keys between the authorized receiver device and the sender device, receive information related to the encryption key selected by the authorized receiver device, generate an optical space communication private key and an RF band communication private key, generate a final private key to be shared with the authorized receiver device based on common key information contained in the generated optical space communication private key and RF band communication private key, and share the final private key with the authorized receiver device.

JP 2019-220762 A

PHYSICAL REVIEW LETTERS 120, 030501 (2018)

When key information generated by a satellite is shared among multiple terrestrial base stations, processing is performed under the assumption that the satellite is trustworthy. However, the key information is stored in the satellite as classical information, so if a backdoor is installed in the satellite and the key information stored in the satellite is stolen, the encryption key generated based on the key information may lose its confidentiality. For this reason, if the encryption key is shared among multiple terrestrial base stations, the security of communications will be lost. Thus, there are safety concerns about leaving important key information on the satellite. Similar concerns also arise when flying objects such as drones are used.

The present invention was devised in consideration of the above-mentioned problems, and its purpose is to provide an encryption key sharing system and method that enables multiple base stations to share an information-theoretically secure encryption key without leaving any key information on the flying object.

The encryption key sharing system according to the first invention is an encryption key sharing system between two secure points via an airborne vehicle, and is characterized by comprising: a key information generating means for generating key information including a first random number and a second random number and used to generate an encryption key; a first storage means for storing the first random number; a first transmission means for transmitting the first random number to a plurality of base stations; a second storage means for deleting the first random number stored by the first storage means and storing the second random number; a second transmission means for transmitting the second random number to the plurality of base stations after the second storage means has stored the second random number; and an encryption key generating means for generating the encryption key to be shared among the plurality of base stations based on the key information including the first random number and the second random number.

The encryption key sharing system according to the second invention is characterized in that in the first invention, the first transmission means or the second transmission means includes transmitting the first random number or the second random number from the flying object to the base station via an optical communication path.

The encryption key sharing system according to the third invention is the first or second invention, characterized in that the key information generating means is provided in the flying object, and generates key information including a second random number after the first transmitting means transmits the first random number to a plurality of the base stations.

The encryption key sharing system according to the fourth invention is the first or second invention, characterized in that the key information generation means is provided in a first base station among the plurality of base stations, and the first base station includes a distribution means for distributing the key information to the flying object.

The encryption key sharing system according to the fifth aspect of the present invention is any one of the first to fourth aspects of the present invention, characterized in that the encryption key generation means includes shortening the bit string of the received key information by a key distillation process.

A cryptographic key sharing method according to a sixth aspect of the present invention is a method for securely sharing an cryptographic key between two points via an aerial vehicle, the method comprising: a key information generation step in which the aerial vehicle generates key information to be used for generating an cryptographic key, the aerial vehicle including a first random number and a second random number; a first storage step in which the aerial vehicle stores the first random number; a first transmission step in which the aerial vehicle transmits the first random number to a plurality of base stations; a second storage step in which the aerial vehicle deletes the first random number stored in the first storage step and stores the second random number; a second transmission step in which the aerial vehicle transmits the second random number to a plurality of the base stations after storing the second random number in the second storage step; and an encryption key generation step in which the base station that has received the first random number and the second random number through the first transmission step and the second transmission step generates the encryption key to be shared among the plurality of the base stations based on the key information including the first random number and the second random number.

According to the first to fifth inventions, the second storage means deletes the first random number stored by the first storage means and stores the second random number. Therefore, when a new random number is transmitted from the flying object, the previously stored random number can be deleted. This allows multiple base stations to share a secure encryption key without leaving any of the key information on the flying object side.

In particular, according to the second invention, the first transmission means or the second transmission means transmits the first random number or the second random number from the flying object to the base station via an optical communication path. Therefore, the reception range is limited to a narrower range than when RF band signals are used. This reduces the possibility of eavesdropping compared to when RF band signals are used.

In particular, according to the third invention, the key information generating means is provided in the flying object, and generates key information including the second random number after the first transmitting means transmits the first random number to the multiple base stations. Therefore, the key information is transmitted to the base station using the flying object as a transmission source. This shortens the time it takes for the key information to be shared among the multiple base stations, and by reducing the number of times the key information is transmitted and received, it is possible to reduce the possibility of eavesdropping during transmission and reception.

In particular, according to the fourth invention, the key information generating means is provided in a first base station among the multiple base stations, and the first base station includes a distribution means for distributing the key information to the air vehicle. Therefore, the air vehicle does not need to include a source of the key information. As a result, there is no need to equip the air vehicle with the key information generating means, and the memory capacity of the air vehicle can be reduced.

In particular, according to the fifth aspect of the invention, the encryption key generation means shortens the bit string of the received key information by key distillation processing. This makes it possible to generate a secure encryption key even if some of the key information is intercepted. This further improves the security of the encryption key.

According to the sixth aspect of the invention, the second storage step deletes the first random number stored in the first storage step and stores the second random number. As a result, the first random number and the second random number constituting the key information are transmitted from the flying object, and none of the key information for generating the encryption key remains on the flying object side. This allows multiple base stations to share the encryption key securely without leaving any of the key information on the flying object side.

FIG. 1 is a schematic diagram showing an example of an encryption key sharing system to which the present invention is applied. FIG. 2 is a block diagram showing an example of the functional configuration of the flying object in the first embodiment. FIG. 3 is a block diagram illustrating an example of a functional configuration of a base station in the first embodiment. FIG. 4 is a block diagram showing an example of a hardware configuration of the flying object in the first embodiment. FIG. 5 is a flowchart showing an example of the operation of the encryption key sharing system in the first embodiment. FIG. 6 is a block diagram showing an example of the functional configuration of a flying object according to the second embodiment. FIG. 7 is a block diagram illustrating an example of a functional configuration of a base station in the second embodiment. FIG. 8 is a flowchart showing an example of the operation of the encryption key sharing system in the second embodiment.

First Embodiment
An encryption key sharing system (wireless communication system) 100 according to an embodiment of the present invention will be described in detail below. FIG. 1 is a schematic diagram showing an example of the encryption key sharing system 100 according to this embodiment. The encryption key sharing system 100 functions as an optical/wireless communication system, and includes an air vehicle 10 and a plurality of base stations 20 (e.g., a first base station 20a, a second base station 20b) that communicate wirelessly with the air vehicle 10. That is, the encryption key sharing system 100 securely shares an encryption key between the plurality of base stations 20 via the air vehicle 10. Note that the number of base stations that communicate wirelessly with the air vehicle 10 is not limited to two, and may be three or more.

The flying object 10 is, for example, an artificial satellite. The artificial satellite orbits in a geostationary orbit (GEO: Geostationary Earth Orbit), which is a geosynchronous orbit around the Earth with an orbital period that coincides with the rotation period of the Earth, or flies in a low Earth orbit (LEO: Low Earth Orbit) or a medium Earth orbit (MEO: Medium Earth Orbit), which revolves independently of the rotation period of the Earth, or even in deep space. The flying object 10 performs optical communication with multiple base stations 20 on the ground (optical communication path A). Note that the flying object 10 is not limited to an artificial satellite, and may be any flying object that can perform optical communication with multiple base stations 20 located on the ground, such as a drone or an unmanned helicopter.

The multiple base stations 20 are base stations for wireless communication that are placed on the ground. The multiple base stations 20 are not limited to base stations that are completely fixed on the ground, but also include mobile base stations that are mounted on vehicles, etc. The multiple base stations 20 perform optical and wireless communication with the flying object 10. Note that the base stations placed on the ground are not limited to the multiple base stations 20, and other base stations may exist.

In the first embodiment, key information generated by the flying object 10 is transmitted to multiple base stations 20 by optical and wireless communication. The key information includes a first random number and a second random number, and is transmitted sequentially from the flying object 10 to the multiple base stations 20. The multiple base stations 20 use the transmitted key information to generate an encryption key to be shared between the base stations. The encryption key shared between the multiple base stations 20 may be, for example, a disposable key that is used once.

Figure 2 is a functional block diagram showing the configuration of the flying object 10. The flying object 10 includes an antenna 11, an optical/wireless communication unit 12, and a control unit 13.

The antenna 11 is used to transmit and receive various signals between the flying object 10 and the multiple base stations 20. The antenna 11 is a well-known antenna used, for example, for optical communication or millimeter wave communication.

The optical and wireless communication unit 12 performs frequency conversion and other various conversion processes required for optical and wireless communication with the flying object 10, and also includes an antenna that converts electrical signals into radio waves, or converts radio waves into electrical signals. The optical and wireless communication unit 12 also includes a converter that converts infrared light, near-infrared light, laser light, or optical signals of any wavelength into electrical signals, or converts electrical signals into optical signals. This optical and wireless communication unit 12 converts signals superimposed on radio waves or optical signals transmitted from outside into electrical signals, and outputs them to the control unit 13. This optical and wireless communication unit 12 also superimposes signals transmitted from the control unit 13 onto radio waves or optical signals, and transmits them to the outside.

The control unit 13 functions as a key information generating means 131, a storage means 132, and a transmission means 133 by following a control program stored in the storage unit 104 described below.

The key information generating means 131 generates key information. The key information is used to generate an encryption key to be used between multiple base stations 20. The key information generating means 131 has, for example, a first key information generating means 131a and a second key information generating means 131b. Note that the key information generating means 131 may have key information generating means other than the first key information generating means 131a and the second key information generating means 131b. For example, it may have a third key information generating means 131c to an n-th key information generating means 131n.

The storage means 132 stores the random numbers in the saving unit 104. The storage means 132 has, for example, a first storage means 132a that stores a first random number and a second storage means 132b that stores a second random number. Note that the storage means 132 may have storage means other than the first storage means 132a and the second storage means 132b. For example, it may have a third storage means 132c to an n-th storage means 132n.

The transmitting means 133 has, for example, a first transmitting means 133a and a second transmitting means 133b. The first transmitting means 133a transmits a first random number to a plurality of base stations 20, and the second transmitting means 133b transmits a second random number to a plurality of base stations 20. Note that the transmitting means 133 may have a transmitting means other than the first transmitting means 133a and the second transmitting means 133b. For example, it may have a third transmitting means 133c to an n-th transmitting means 133n.

Figure 3 is a functional block diagram showing the configuration of each base station 20. Each base station 20 includes an antenna 21, an optical/wireless communication unit 22, a memory unit 23, and a control unit 24.

The antenna 21 is used to transmit and receive various signals between the multiple base stations 20 and the flying object 10. The antenna 21 transmits the signal output by the optical and wireless communication unit 22 to the flying object 10 as radio waves. The antenna 21 also converts the optical and wireless communication received from the flying object 10 into a signal and outputs the signal to the optical and wireless communication unit 22.

The optical and wireless communication unit 22 performs frequency conversion and other various conversion processes required for optical and wireless communication with the flying object 10, and also includes an antenna that converts electrical signals into radio waves, or converts radio waves into electrical signals. The optical and wireless communication unit 22 also includes a converter that converts infrared light, near-infrared light, laser light, or optical signals of any wavelength into electrical signals, or converts electrical signals into optical signals. This optical and wireless communication unit 22 converts signals superimposed on radio waves or optical signals transmitted from outside into electrical signals, and outputs them to the control unit 24. This optical and wireless communication unit 22 also superimposes signals transmitted from the control unit 24 onto radio waves or optical signals, and transmits them to the outside.

The storage unit 23 stores various information acquired by the first base station 20a. The storage unit 23 includes, for example, a RAM (Random Access Memory) and a ROM (Read Only Memory), and stores programs executed by the control unit 24, etc.

The control unit 24 functions as an encryption key generating means 241 by following the control program stored in the memory unit 23.

The encryption key generation means 241 generates an encryption key to be shared among multiple base stations 20 based on key information including the first random number and the second random number transmitted from the flying object 10.

<Flying object 10>
4 is a schematic diagram showing an example of the components included in the flying object 10. The flying object 10 includes an antenna 11, a CPU 101, a ROM 102, a RAM 103, a storage unit 104, and I/Fs 105 to 106. Each component is connected by an internal bus 107.

The antenna 11 is used to transmit and receive various signals, such as terminal signals, to and from multiple base stations 20. The CPU (Central Processing Unit) 101 controls the entire flying object 10. The ROM (Read Only Memory) 102 stores the operating code of the CPU 101. The RAM (Random Access Memory) 103 is a working area used when the CPU 101 is operating.

Various information is stored in the storage unit 104. A data storage device such as a hard disk drive (HDD) or a solid state drive (SSD) is used as the storage unit 104. Each function shown in FIG. 2 is realized by the CPU 101 using the RAM 103 as a working area to execute a program stored in the storage unit 104 or the like. The storage unit 104 has a storage capacity sufficient to store only either the first random number or the second random number. In other words, the capacity of the storage area pre-allocated in the storage unit 104 for storing key information is set to be smaller than the combined capacity of the first random number and the second random number.

I/F 105 is an interface component for connecting to antenna 11. I/F 106 is an interface component for connecting to a communication network 200 such as a network.

(First embodiment: operation of encryption key sharing system 100)
Next, a description will be given of the operation of the encryption key sharing system 100 according to this embodiment. Fig. 5 is a flow chart showing an example of the operation of the encryption key sharing system 100 according to this embodiment.

As shown in FIG. 5, for example, the encryption key sharing system 100 executes a first key information generation step S10, a first storage step S20, a first transmission step S30, a second key information generation step S40, a second storage step S50, a second transmission step S60, and an encryption key generation step S70.

<First key information generation step S10>
First, the first key information generating means 131a generates key information used to generate an encryption key (first key information generating step S10). Specifically, in the flying object 10, a first random number is generated.

<First storage step S20>
Next, the first storage means 132a stores the first random number (first storage step S20). In the flying object 10, the generated first random number is stored in the storage unit 104, for example.

<First transmission step S30>
Next, the first transmitting means 133a transmits the first random number to the plurality of base stations 20 (first transmitting step S30). The first random number stored in the storage unit 104 of the flying object 10 is transmitted from the flying object 10 to the plurality of base stations 20 via, for example, the optical communication path A.

<Second key information generation step S40>
Next, the second key information generating means 131b generates a second random number different from the first random number (second key information generating step S40). In the flying object 10, after the first transmitting means transmits the first random number to the multiple base stations 20, the second random number different from the first random number is generated.

<Second storage step S50>
Next, the second storage means 132b deletes the first random number and stores the second random number (second storage step S50). In the flying object 10, the second random number is stored in the storage unit 104, for example.

<Second Transmission Step S60>
Next, the second storage means 132b transmits the second random number to the plurality of base stations 20 (second transmission step S60). The second random number stored in the storage unit 104 of the flying object 10 is transmitted from the flying object 10 to the plurality of base stations 20 via, for example, the optical communication path A.

The above process from the generation of the first random number in the first key information generation step S10 to the transmission of the second random number in the second transmission step S60 to the multiple base stations 20 may be performed periodically multiple times (e.g. 10 times). For example, the generation, storage, and transmission of the third random number through the generation, storage, and transmission of the nth random number may be performed. In this way, the base station 20 obtains key information including the multiple random numbers.

<Encryption key generation step S70>
Next, the encryption key generating means 241 generates an encryption key (encryption key generating step S70). The first base station 20a generates an encryption key shared among the multiple base stations 20 using key information including the first random number and the second random number transmitted from the flying object 10. Specifically, the first base station 20a transmits the key information received via the public communication channel B to the second base station 20b by a key distillation process including an error correction process and a privacy amplification process. The second base station 20b estimates an error rate based on (for example, by comparing) the two pieces of key information received from the flying object 10 and the first base station 20a. Next, the second base station 20b performs an error correction process on each piece of key information. Note that the first base station 20a and the second base station 20b may perform the reverse process.

Then, the multiple base stations 20 execute a privacy amplification process. The multiple base stations 20 estimate the amount of leaked information for the key information after error correction. For example, the multiple base stations 20 estimate random numbers that may have been intercepted by a third party, taking into account the beam diameter of the light beam emitted from the flying object 10 and the effects of atmospheric turbulence. Then, the random numbers that may have been intercepted are deleted from the random number sequence (key information) to shorten the random number sequence. An encryption key is generated based on the shortened random number sequence. The security of the encryption keys for the multiple base stations 20 is confirmed by comparing the hash values of the encryption keys.

In this way, the key distillation process allows multiple base stations 20 to share a secure encryption key that is less susceptible to eavesdropping via the public communication channel B.

By performing the above-described operations, the operation of the encryption key sharing system 100 in this embodiment is completed. Note that each of the above-described steps S10 to S60 may be performed multiple times.

According to this embodiment, after the first random number stored by the first storage means 132a is transmitted to the base station, the second storage means 132b deletes the first random number and stores the second random number. Therefore, when a new random number is transmitted from the flying object 10, the previously stored random number can be deleted. This allows multiple base stations to share a secure encryption key without leaving all of the key information on the flying object 10 side.

Furthermore, according to this embodiment, the first transmitting means 133a or the second transmitting means 133b transmits the first random number or the second random number from the flying object 10 to multiple base stations 20 via the optical communication path A. Therefore, the reception range is limited to a narrower range than when RF band signals are used. This reduces the possibility of eavesdropping compared to when RF band communication is used.

Furthermore, according to this embodiment, the first key information generating means 131a and the second key information generating means 131b are provided in the flying object 10, and generate key information including the second random number after the first transmitting means 133a transmits the first random number to the base station. Therefore, the key information is transmitted to multiple base stations 20 using the flying object 10 as a transmission source. This shortens the time it takes for the key information to be shared among multiple base stations 20, and by reducing the number of times the key information is transmitted and received, the possibility of eavesdropping during transmission and reception can be reduced.

Furthermore, according to this embodiment, the encryption key generation means 241 shortens the bit string of the received key information by key distillation processing. Therefore, it is possible to generate a secure encryption key even if some of the information is intercepted. This further improves the security of the encryption key. Note that the information-theoretic security of the encryption key is premised on the establishment of a wiretap model for quantum key distribution or physical layer encryption.

Second Embodiment
Next, an encryption key sharing system 100 according to a second embodiment will be described. The difference between the above-mentioned embodiment and the second embodiment is that a key information generating means is provided in a base station 60. Note that a description of the same contents as those in the above-mentioned embodiment will be omitted. The encryption key sharing system 100 according to the second embodiment has an air vehicle 50 and a plurality of base stations 60 (for example, a first base station 60a and a second base station 60b).

Figure 6 is a functional block diagram showing the configuration of a flying object 50 according to the second embodiment. As in the first embodiment, the flying object 10 includes an antenna 11, an optical and wireless communication unit 12, and a control unit 13. The configurations and functions of the antenna 11 and the optical and wireless communication unit 12 are similar to those of the flying object 10 according to the first embodiment.

The control unit 13 functions as a storage means 132 and a transmission means 133. That is, the second embodiment is different from the first embodiment in that the control unit 13 does not include a key information generation means.

The storage means 132 has a first storage means 132a and a second storage means 132b. The first storage means 132a stores a first random number distributed from the first base station 60a, and the second storage means 132b stores a second random number distributed from the first base station 60a. As in the first embodiment, the storage means 132 may have storage means other than the first storage means 132a and the second storage means 132b.

The transmitting means 133 has, for example, a first transmitting means 133a and a second transmitting means 133b. The first transmitting means 133a transmits a first random number to a plurality of base stations 60, and the second transmitting means 133b transmits a second random number to a plurality of base stations 60. Note that, as in the first embodiment, the transmitting means 133 may have a transmitting means other than the first transmitting means 133a and the second transmitting means 133b.

Figure 7 is a functional block diagram showing the configuration of each base station 60. The base station 60 includes an antenna 21, an optical/wireless communication unit 22, a storage unit 23, and a control unit 24.

By following the control program stored in the memory unit 23, the control unit 24 functions not only as the encryption key generating means 241, but also as the key information generating means 24a and the distribution means 24b.

The key information generating means 24a generates key information used to generate an encryption key. The key information is used to generate an encryption key used between multiple base stations 60. The key information generating means 24a may generate key information including the first random number and the second random number as one piece of key information, or may generate the key information including the first random number and the key information including the second random number separately.

The distribution means 24b distributes the key information to the flying object 10. The distribution means 24b sequentially distributes the key information including the first random number and the key information including the second random number to the flying object 10.

(Second embodiment: operation of encryption key sharing system 100)
Next, a description will be given of the operation of the encryption key sharing system 100 in the second embodiment. Fig. 8 is a flow chart showing an example of the operation of the encryption key sharing system 100 in this embodiment.

As shown in FIG. 8, for example, the encryption key sharing system 100 executes a key information generation step S110, a distribution step S120, a first storage step S130, a first transmission step S140, a second storage step S150, a second transmission step S160, and an encryption key generation step S170.

<Key information generation step S110>
First, the key information generating means 24a generates key information used to generate an encryption key (key information generating step S110). For example, the first base station 60a generates key information including a first random number and a second random number.

<Distribution Step S120>
Next, the distribution means 24b distributes the key information to the flying object 10 (distribution step S120). The key information stored in the memory unit 23 is distributed from the first base station 60a to the flying object 50.

<First storage step S130>
Next, the first storage means 132a stores the first random number (first storage step S130). Specifically, in the flying object 10, the first random number is stored in the storage unit 104, for example.

<First transmission step S140>
Next, the first transmitting means 133a transmits the first random number to the multiple base stations 60 (first transmitting step S140). The first random number stored in the storage unit 104 of the flying object 50 is transmitted from the flying object 50 to the multiple base stations 60, for example, via the optical communication path A. The first transmitting step S140 is, for example, a process of transmitting the first random number from the flying object 50 to a base station 60 other than the first base station 60a.

<Second storage step S150>
Next, the second storage means 132b deletes the first random number and stores the second random number (second storage step S150). In the flying object 50, the second random number is stored in the storage unit 104, for example.

<Second Transmission Step S160>
Next, the second transmitting means 133b transmits the second random number to the plurality of base stations 60 (second transmitting step S160). The second random number stored in the storage unit 104 of the flying object 50 is transmitted from the flying object 50 to the plurality of base stations 60 via, for example, the optical communication path A.

The above process from the generation of the first random number in the key information generation step S110 to the transmission of the second random number to the multiple base stations 60 in the second transmission step S160 may be performed periodically multiple times (e.g. 10 times). For example, the storage and transmission of the third random number through the storage and transmission of the nth random number may be performed. As a result, each base station 60 obtains key information including multiple random numbers.

<Encryption key generation step S170>
Next, the encryption key generating means 241 generates an encryption key (encryption key generating step S170). The first base station 60a generates an encryption key shared among the multiple base stations 60 using key information including the first random number and the second random number transmitted from the flying object 10. Details of the key distillation process including the error correction process and the privacy amplification process are the same as those in the first embodiment, so detailed explanations will be omitted. The key distillation process shortens the bit string of the received key information shared among the multiple base stations 60, so a secure encryption key can be obtained.

According to this embodiment, the key information generation means is provided, for example, in a first base station 60a among the multiple base stations, and the first base station 60a has a distribution means for distributing key information to the flying object 50. The key information generated in the first base station 60a and distributed to the flying object 50 is transmitted to the second base station 60b. Therefore, the flying object 50 does not need to have a source for generating key information. As a result, there is no need to install a key information generation means in the flying object 50, and the memory capacity of the flying object can be reduced.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

10: Flying object 11: Antenna 12: Optical/wireless communication unit 13: Control unit 131: Key information generating means 131a: First key information generating means 131b: Second key information generating means 132: Storage means 132a: First storage means 132b: Second storage means 133: Transmission means 133a: First transmission means 133b: Second transmission means 20: Base station 20a: First base station 20b: Second base station 21: Antenna 22: Optical/wireless communication unit 23: Storage unit 24: Control unit 24a: Key information generating means 24b: Distribution means 241: Encryption key generating means 50: Flying object 60: Base station 60a: First base station 60b: Second base station 100: Encryption key sharing system 101: CPU
102: ROM
103: RAM
104: Storage unit 105: I/F
106: I/F
107: Internal bus 200: Communication network

Claims (6)

A system for securely sharing an encryption key between two points via an aerial vehicle, comprising:
a key information generating means for generating key information including a first random number and a second random number and for use in generating an encryption key;
a first storage means for storing the first random number;
a first transmitting means for transmitting the first random number to a plurality of base stations;
a second storage means for deleting the first random number stored by the first storage means and storing the second random number;
a second transmission means for transmitting the second random number to a plurality of the base stations after the second storage means stores the second random number;
and an encryption key generation means for generating the encryption key to be shared among a plurality of the base stations based on the key information including the first random number and the second random number. The encryption key sharing system according to claim 1 , characterized in that the first transmission means or the second transmission means includes transmitting the first random number or the second random number from the flying object to the base station via an optical/wireless communication path. 3. The encryption key sharing system according to claim 1 or 2, wherein the key information generating means is provided in the flying object, and generates key information including the second random number after the first transmitting means transmits the first random number to the plurality of base stations. the key information generating means is provided in a first base station among the plurality of base stations,
3. The encryption key sharing system according to claim 1, wherein the first base station comprises a distribution unit that distributes the key information to the flying object. 5. The encryption key sharing system according to claim 1, wherein the encryption key generation means shortens a bit string of the received key information by a key distillation process. A method for securely sharing an encryption key between two points via an airborne vehicle, comprising the steps of:
a key information generating step of generating key information used to generate an encryption key, the key information including a first random number and a second random number;
a first storage step in which the flying object stores the first random number;
a first transmission step in which the flying object transmits the first random number to a plurality of base stations;
a second storage step in which the flying object deletes the first random number stored in the first storage step and stores the second random number;
a second transmission step of transmitting the second random number to a plurality of the base stations after the flying object stores the second random number in the second storage step;
and an encryption key generation step in which the base station, having received the first random number and the second random number through the first transmission step and the second transmission step, generates the encryption key to be shared among a plurality of the base stations based on the key information including the first random number and the second random number.

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