JP2023149074A - Encryption key sharing system - Google Patents

Abstract

To provide an encryption key sharing system in which distance over which encryption keys can be shared is long and a large amount of encryption keys can be shared.SOLUTION: An encryption key sharing system 1 includes: a low orbit satellite 3A; a geostationary satellite 2 that shares keys K1 and K2 of the low orbit satellite 3A and a ground station 3B by line-of-sight communication quantum key distribution or physical layer encryption, obtains calculation data for decrypting the key K1 of the low orbit satellite 3A by exclusive OR of the keys K1 and K2, and transmits the calculation data to the ground station 3B via an authenticated public channel 5; and the ground station 3B that decrypts the key K1 of the low orbit satellite 3A by exclusive OR of the received calculation data and the key K2 of the ground station 3B.SELECTED DRAWING: Figure 1

Description

The present invention relates to an encryption key sharing system.

Quantum key distribution makes it possible to share cryptographic keys that are information-theoretically secure, and as long as one-time pads are used correctly, the security of cryptographic keys is guaranteed by the laws of physics. Furthermore, in quantum key distribution, in addition to optical fibers, propagation of light beams in free space is also assumed as a light transmission path. Information-theoretically secure means that it has been mathematically proven, based on information theory, that it is impossible for an eavesdropper to decipher the ciphertext, even if it is assumed that the eavesdropper has infinite computing power. It means that.

In quantum key distribution using optical fibers, the distance over which encryption keys can be shared is limited to about 100 km due to losses associated with optical transmission. Therefore, in terrestrial quantum key distribution, it is difficult to share encryption keys at distances of several hundred to several thousand kilometers.

Therefore, conventional techniques related to quantum key distribution using low orbit satellites have been proposed (for example, Patent Documents 1 and 2 and Non-Patent Documents 1 to 4). In these conventional technologies, a first encryption key is shared between the first ground station and the low orbit satellite (first step), and a second encryption key is shared between the second ground station and the low orbit satellite. (second step). In these conventional technologies, for example, when the low-orbit satellite enters the field of view of the first ground station again, the low-orbit satellite sends a second signal to the first ground station using a normal data communication line. Data obtained by anonymizing the encryption key with the first encryption key (calculating exclusive OR) is transmitted (third step). In this way, with these conventional techniques, the second encryption key can ultimately be shared between the first ground station and the second ground station that are located far apart.

China Patent Application Publication No. 112054852 China Patent Application Publication No. 111431623

J. Yin, et al., “Satellite-based entanglement distribution over 1200 kilometers”, Science 356, pp. 1140-1144, 2017. S. K. Liao, et al., “Long-distance free-space quantum key distribution in daylight towards inter-satellite communication”, Nat. Photon. 11, 509, 2017. S. K. Liao, et al., “Satellite-Relayed Intercontinental Quantum Network”, Phys. Rev. Lett., 120(3), 030501, 2018. Y. A. Chen, et al., “Satellite testing of a gravitationally induced quantum decoherence model”, Nature 589, pp. 214-219, 2021.

However, in the above-mentioned conventional technology, since the low orbit satellite moves in the sky at high speed, the time for each communication with the ground station is limited to about 10 minutes at the maximum. For this reason, in the conventional technology described above, sufficient communication time cannot be secured to generate an encryption key, and the amount of encryption keys that can be shared (the number of bits of the encryption key) becomes extremely small.

Therefore, an object of the present invention is to provide an encryption key sharing system that allows encryption keys to be shared over a long distance and in which a large amount of encryption keys can be shared.

In order to solve the above problems, an encryption key sharing system according to the present invention shares an encryption key between a first node and a second node using line-of-sight quantum key distribution or physical layer encryption relayed by a geostationary satellite. A cryptographic key sharing system for a geostationary satellite, wherein a geostationary satellite shares a first cryptographic key and a second cryptographic key between a first node and a second node, respectively, by line-of-sight quantum key distribution or physical layer cryptography, A calculation is performed using the exclusive OR of the first encryption key and the second encryption key, and the calculation result is transmitted to a second node via an authenticated public communication channel, and the second node receives the calculation result and the second encryption key. The configuration is such that the first encryption key is decrypted by calculating the exclusive OR with the first encryption key.

According to this configuration, the cryptographic key sharing system makes it possible to share cryptographic keys between the geostationary satellite and each node by using line-of-sight quantum key distribution or physical layer cryptography via the geostationary satellite. . This makes it possible to increase the distance at which encryption keys can be shared, that is, the distance between the first node and the second node. Here, since a sufficiently long communication time can be secured between the geostationary satellite and the node, the amount of encryption keys that can be shared increases.

According to the present invention, the distance over which encryption keys can be shared is long, and a large amount of encryption keys can be shared.

(a) to (c) are schematic diagrams of an encryption key sharing system according to the first embodiment. FIG. 2 is a block diagram showing the configuration of a first subsystem of the encryption key sharing system in the first embodiment. In the first embodiment, (a) is a block diagram showing the configuration of a receiving optical section, and (b) is a block diagram showing the configuration of a transmitting optical section. FIG. 2 is a block diagram showing the configuration of a second subsystem of the encryption key sharing system in the first embodiment. FIG. 2 is a sequence diagram showing the operation of the encryption key sharing system according to the first embodiment. (a) to (c) are schematic diagrams of an encryption key sharing system according to a second embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the second embodiment. (a) and (b) are schematic diagrams of an encryption key sharing system according to a third embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the third embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the third embodiment. (a) to (c) are schematic diagrams of an encryption key sharing system according to a fourth embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the fourth embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the fourth embodiment. FIG. 3 is a schematic diagram of an encryption key sharing system according to a fifth embodiment. FIG. 7 is a block diagram showing the configuration of a third subsystem of the cryptographic key sharing system in the fifth embodiment. FIG. 7 is a sequence diagram showing the operation of the encryption key sharing system according to the fifth embodiment.

Embodiments of the present invention will be described below with reference to the drawings. However, each embodiment described below is for embodying the technical idea of the present invention, and unless there is a specific description, the present invention is not limited to the following. For example, all possible combinations of geostationary satellites and nodes such as low-orbit satellites and ground stations are used as receivers or transmitters for line-of-sight communications, depending on the actual situation. is assumed. Further, the same means may be denoted by the same reference numerals, and the description thereof may be omitted.

(First embodiment)
[Overview of encryption key sharing system]
With reference to FIG. 1, an overview of an encryption key sharing system 1 according to the first embodiment will be described.
The cryptographic key sharing system 1 shares cryptographic keys between the low orbit satellite 3A and the ground station 3B using line-of-sight quantum key distribution or physical layer cryptography relayed by the geostationary satellite 2. As shown in FIG. 1(a), the encryption key sharing system 1 includes a geostationary satellite 2, a low orbit satellite 3A (first node) as a node 3, and a ground station 3B (second node). Further, in FIG. 1, a line-of-sight communication channel 4, an authenticated public communication channel 5, and the earth E are illustrated.

The geostationary satellite 2 is a communication satellite orbiting in a geostationary orbit at an altitude of 36,000 km above the equator. Here, the geostationary satellite 2 shares a first encryption key and a second encryption key between the first node and the second node, respectively, by line-of-sight quantum key distribution or physical layer cryptography. Furthermore, the geostationary satellite 2 performs a calculation using the exclusive OR of the first encryption key and the second encryption key, and transmits the calculation result to the second node via the authenticated public communication channel 5.

After the first node and the second node share the first encryption key, the first node uses the first encryption key to anonymize data and communicate. At this time, the second node decrypts the first encryption key by calculating the exclusive OR of the calculation result from the geostationary satellite 2 and the second encryption key. For example, in general, the node 3 includes one or more ground stations 3B, low orbit satellites 3A, and either a maritime station or an aviation station described later.

The low orbit satellite 3A is, for example, a communication satellite orbiting in a low orbit at an altitude of about 400 to 1200 km, and has a function as a node 3.
The ground station 3B is a node 3 placed on the ground. For example, the ground station 3B is a fixed station fixed at a predetermined position on the ground, or a mobile station mounted on a moving vehicle.

The line-of-sight communication channel 4 is a communication line for performing line-of-sight communication. Here, line-of-sight communication refers to communication in a state where there is no obstruction between the geostationary satellite 2 and the node 3 and they can see each other. For example, line-of-sight communication includes optical communication between a low-orbit satellite and a ground station, and optical communication between a high-altitude geostationary orbit satellite and a ground station.

Because line-of-sight communication channel 4 uses highly directional laser light, an eavesdropper can install a wiretapping device in the center of the light beam and perform some processing on all optical signals after receiving them, without being detected by the sender and receiver. In practice, it is extremely difficult to carry out an active attack such as retransmission. In addition, line-of-sight quantum key distribution and physical layer cryptography use light beams propagating through line-of-sight channels 4 in free space to share information-theoretically secure cryptographic keys, and are more secure than quantum key distribution. , has the advantage that the encryption key generation speed is fast and encryption keys can be distributed over long distances.

The authenticated public communication channel 5 is an authenticated public communication channel. For example, the authenticated public communication channel 5 is used to send and receive the state of the line-of-sight channel 4, the result of key distillation processing, calculation data of exclusive OR of encryption keys, and anonymized data for significant information. .

Note that physical layer cryptography is common, so a detailed explanation will be omitted (References 1 to 4).
Reference 1: Z. Pan et al., “Secret-key distillation across a quantum wiretap channel under restricted eavesdropping,” Phys. Rev. Applied, vol. 14, no. 2, 024044, 2020.
Reference 2: H.Endo, et al., OSA Continuum 3 pp. 2525-2543, 2020.
Reference 3: European Patent No. 3337063 Reference 4: International Publication No. 2019/139544

Encrypted communication in the encryption key sharing system 1 will be described below.
First, as shown in FIG. 1(a), the cryptographic key sharing system 1 uses line-of-sight quantum key distribution or physical layer encryption to exchange a key _K1 (first cryptographic key) between a geostationary satellite 2 and a low-orbit satellite 3A. ) to generate and share. Furthermore, the cryptographic key sharing system 1 generates and shares a key K ₂ (second cryptographic key) between the geostationary satellite 2 and the ground station 3B using line-of-sight quantum key distribution or physical layer cryptography. That is, the geostationary satellite 2 shares the keys K ₁ and K ₂ via the line-of-sight channel 4 .

Next, as shown in FIG. 1(b), the encryption key sharing system 1 calculates the exclusive OR of the keys K ₁ and K ₂ on the geostationary satellite 2, and via the authenticated public communication channel 5, The calculated data α is transmitted to the ground station 3B. Then, the cryptographic key sharing system 1 decrypts the key _K1 of the low orbit satellite 3A by calculating the exclusive OR of the calculation data α and the key _K2 of the ground station 3B at the ground station 3B. Thereby, the encryption key sharing system 1 can share the key _K1 between the low orbit satellite 3A and the ground station 3B. As a result, as shown in FIG. 1(c), the encryption key sharing system 1 can use this key _K1 as an encryption key to perform encrypted communication between the low orbit satellite 3A and the ground station 3B. .

[Configuration of encryption key sharing system]
<Geostationary satellite>
The configuration of the encryption key sharing system 1 will be explained with reference to FIGS. 2 to 4. In FIG. 2, a combination of the geostationary satellite 2 and the low orbit satellite 3A is extracted as the cryptographic key sharing subsystem 10.
As shown in FIG. 2, the geostationary satellite 2 includes a line-of-sight communication section 20, a key management section 21, and a data communication section 22.

The line-of-sight communication unit 20 is a general unit that shares a first encryption key and a second encryption key using line-of-sight communication quantum key distribution or physical layer cryptography. In this embodiment, the line-of-sight communication unit 20 shares a key _K1 with the low orbit satellite 3A, and shares a key _K2 with the ground station 3B. Further, the line-of-sight communication section 20 includes a reception optical section 200, a key distillation section 210, and a communication channel state monitoring section 220.

The receiving optical section 200 receives the optical signal 40 from the transmitting optical section 300 via the line-of-sight channel 4, and decodes random number bits from the received optical signal 40. As shown in FIG. 3A, the receiving optical unit 200 includes a light receiving unit 201 that receives an optical signal 40, an opto-electrical unit 202 that converts the optical signal into an electrical signal, and a decoding unit 203 that decodes the electrical signal. Be prepared.

The key distillation unit 210 generates an encryption key from the random number bit sequence of the receiving optical unit 200 by key distillation processing via the authenticated public communication channel 5. In this embodiment, the key distillation unit 210 generates keys K ₁ and K ₂ by key distillation processing, and outputs the generated keys K ₁ and K ₂ to the key management unit 21 .

Note that the key distillation process is a process performed while exchanging information over the authenticated public communication channel 5 in order to generate equally secure encryption keys from the bit strings of the receiving optical unit 200 and the transmitting optical unit 300. be. Since this key distillation process itself is common, further explanation will be omitted.

The channel condition monitoring unit 220 is a general unit that measures the condition of the line-of-sight channel 4 (for example, the atmospheric fluctuation 42 in FIG. 4). Here, the communication channel state monitoring unit 220 measures the state of the line-of-sight communication channel 4 by observing a sufficiently intense laser beam (probe light 41) irradiated by a communication channel state monitoring unit 320, which will be described later. Further, the communication channel state monitoring section 220 may irradiate the communication channel state monitoring section 320 with probe light.

The key management unit 21 obtains calculation data for the exclusive OR of the first encryption key and the second encryption key. In this embodiment, the key management unit 21 stores the keys K ₁ and K ₂ input from the key distillation unit 210, and calculates the exclusive OR of the keys K ₁ and K ₂ . Then, the key management unit 21 outputs calculation data α, which is the calculation result, to the data communication unit 22.

The data communication unit 22 transmits the calculation data α obtained by the key management unit 21 to the second node (ground station 3B) via the authenticated public communication channel 5.

<Low orbit satellite>
As shown in FIG. 2, the low orbit satellite 3A includes a line-of-sight communication section 30, a key management section 31, and a data communication section 32.

The line-of-sight communication unit 30 is a general unit that shares a first encryption key (key K ₁ of the low orbit satellite 3A) with the geostationary satellite 2 by line-of-sight communication quantum key distribution or physical layer cryptography. Further, the line-of-sight communication unit 30 includes a transmission optical unit 300, a key distillation unit 310, and a communication path status monitoring unit 320.

The transmission optical unit 300 encodes the random number bits into an optical signal 40 and transmits the encoded optical signal 40 via the line-of-sight channel 4 at a preset intensity. As shown in FIG. 3B, the transmission optical unit 300 includes a light emitting unit 301 that emits light, a light intensity adjustment unit 302 that adjusts the intensity of the optical signal 40, and an encoder that encodes random number bits into the optical signal 40. section 303 and a light transmitting section 304 that transmits the optical signal 40.

The key distillation unit 310 generates a first encryption key (the key K ₁ of the low orbit satellite 3A) from the random number bit sequence of the transmission optical unit 300 by a key distillation process via the authenticated public communication channel 5. Further, the key distillation unit 310 outputs the generated first encryption key to the transmission optical unit 300 and the key management unit 31.

The communication channel state monitoring section 320 is a general one that irradiates the communication channel state monitoring section 220 with the probe light 41. Further, the communication channel state monitoring unit 320 may measure the state of the line-of-sight communication channel 4 by observing the probe light emitted by the communication channel state monitoring unit 220.

The key management unit 31 stores the key _K1 input from the key distillation unit 310. For example, the key management unit 31 stores the key _K1 in a memory (not shown).

The data communication unit 32 receives calculation data α from the geostationary satellite 2 via the authenticated public communication channel 5.

<Ground station>
As shown in FIG. 4, the ground station 3B has the same configuration as the low orbit satellite 3A, and includes a line-of-sight communication section 30B, a key management section 31B, and a data communication section 32. In addition, in FIG. 4, the combination of the geostationary satellite 2 and the ground station 3B is extracted as the cryptographic key sharing subsystem 11.

The line-of-sight communication unit 30B is a general unit that shares a second encryption key (the key K ₂ of the ground station 3B) with the geostationary satellite 2 by line-of-sight communication quantum key distribution or physical layer cryptography. Further, the line-of-sight communication section 30 includes a transmission optical section 300, a key distillation section 310B, and a communication channel state monitoring section 320.

The key distillation unit 310B generates a second encryption key (key K ₂ of the ground station 3B) from the random number bit sequence of the transmission optical unit 300 by key distillation processing via the authenticated public communication channel 5. Further, the key distillation section 310 outputs the generated encryption key to the transmission optical section 300 and the key management section 31.

The key management unit 31B stores the second encryption key, that is, the key _K2 input from the key distillation unit 310B. Further, the key management unit 31B decrypts the first encryption key by calculating the exclusive OR of the calculation data received by the data communication unit 32 and the second encryption key. In this embodiment, the key management unit 31B decrypts the key _K1 of the low orbit satellite 3A by calculating the exclusive OR of the calculation data α and the key _K2 of the ground station 3B.

[Operation of encryption key sharing system]
The operation of the encryption key sharing system 1 will be explained with reference to FIG.
As shown in FIG. 5, in step S1, the low orbit satellite 3A transmits random number bits to the geostationary satellite 2 via the line-of-sight channel 4. Note that step S1 in FIG. 5 is illustrated with a thick arrow to indicate that the line-of-sight communication channel 4 is used.
In step S2, the geostationary satellite 2 and the low orbit satellite 3A generate and share a secure key _K1 through key distillation processing.
In step S3, the low orbit satellite 3A stores the key _K1 .
In step S4, the geostationary satellite 2 stores the key _K1 .

In step S5, the ground station 3B transmits random number bits to the geostationary satellite 2 via the line-of-sight channel 4.
In step S6, the geostationary satellite 2 and the ground station 3B generate and share a secure key _K2 by key distillation processing.
In step S7, the geostationary satellite 2 stores the key _K2 .
In step S8, the ground station 3B stores the key _K2 .

In step S9, the geostationary satellite 2 obtains the exclusive OR of the keys K ₁ and K ₂ stored in steps S4 and S7 as calculation data α.
In step S10, the geostationary satellite 2 transmits the calculation data α to the ground station 3B via the authenticated public communication channel 5. Note that an "x" is shown because the geostationary satellite 2 ends its operation in step S10.
In step S11, the ground station 3B decrypts the key _K1 of the low orbit satellite 3A by calculating the exclusive OR of the calculation data α and the key _K2 stored in step S8.
In step S12, the ground station 3B stores the key _K1 of the low orbit satellite 3A.
In step S13, the ground station 3B notifies the low orbit satellite 3A of the completion of sharing the key _K1 .

Thereafter, in the encryption key sharing system 1, the data can be anonymized and encrypted communication can be performed between the low orbit satellite 3A and the ground station 3B using the key _K1 .

[Action/Effect]
As described above, the cryptographic key sharing system 1 uses line-of-sight quantum key distribution or physical layer cryptography to communicate between the geostationary satellite 2 at an altitude of 36,000 km above the equator and the low-orbit satellite 3A or ground station 3B. Encryption keys can be shared between users. Here, since the encryption key sharing system 1 can secure a sufficiently long communication time, many encryption keys can be shared between the geostationary satellite 2 and the low orbit satellite 3A or the ground station 3B. Therefore, the encryption key sharing system 1 can increase the amount of encryption keys that can be shared between the low orbit satellite 3A and the ground station 3B using the geostationary satellite 2 as a relay point.

In other words, the encryption key sharing system 1 alleviates the limitations of the conventional technology, which was limited to about 10 minutes at most per pass, and stably shares many keys over a long period of time between the low orbit satellite 3A and the ground station 3B. can be shared between Thereby, the encryption key sharing system 1 can easily share encryption keys in a wide range including from the surface of the earth E to the orbit of a geostationary satellite.

In addition, in the encryption key sharing system 1, the low orbit satellite 3A is the sender (first node) of the shared encryption key, and the ground station 3B is the receiver (second node) of the shared encryption key. Although described above, the invention is not limited thereto. That is, in the encryption key sharing system 1, the low orbit satellite 3A may be the recipient of the shared encryption key, and the ground station 3B may be the sender of the shared encryption key.

(Second embodiment)
[Overview of encryption key sharing system]
With reference to FIG. 6, an outline of an encryption key sharing system 1B according to the second embodiment will be explained, and the points that are different from the first embodiment will be described.
As shown in FIG. 6(a), the encryption key sharing system 1B differs from the first embodiment in that it includes a low orbit satellite 3D instead of the ground station 3B in FIG. 1 as a recipient of the shared encryption key. . That is, the encryption key sharing system 1B includes a geostationary satellite 2, a low orbit satellite 3C, and a low orbit satellite 3D.

Here, the encryption key for the low orbit satellite 3C is referred to as a key _K3 , and the encryption key for the low orbit satellite 3D is referred to as a key _K4 . Note that the encrypted communication in the encryption key sharing system 1B is the same as in the first embodiment except that the key K ₃ is used instead of the key K ₁ and the key K ₄ is used instead of the key K ₂ , so the explanation will be omitted. Omitted. Further, the configuration of the low orbit satellite 3C is the same as the low orbit satellite 3A in FIG. 2, and the configuration of the low orbit satellite 3D is the same as the ground station 3B in FIG. 4, so a description thereof will be omitted.

[Operation of encryption key sharing system]
The operation of the encryption key sharing system 1B will be explained with reference to FIG.
In addition, in FIG. 7, the set of the geostationary satellite 2 and the low orbit satellite 3D is illustrated as the encryption key sharing subsystem 10B.

As shown in FIG. 7, in step S20, the low orbit satellite 3C transmits random number bits to the geostationary satellite 2 via the line-of-sight channel 4.
In step S21, the geostationary satellite 2 and the low orbit satellite 3C generate and share a secure key _K3 through key distillation processing.
In step S22, the low orbit satellite 3C stores the key _K3 .
In step S23, the geostationary satellite 2 stores the key _K3 .

In step S24, the low orbit satellite 3D transmits random number bits to the geostationary satellite 2 via the line-of-sight channel 4.
In step S25, the geostationary satellite 2 and the low orbit satellite 3D generate and share a secure key _K4 through key distillation processing.
In step S26, the geostationary satellite 2 stores the key _K4 .
In step S27, the low orbit satellite 3D stores the key _K4 .

In step S28, the geostationary satellite 2 obtains the exclusive OR of the keys K ₃ and K ₄ stored in steps S23 and S26 as calculation data α.
In step S29, the geostationary satellite 2 transmits the calculation data α to the low orbit satellite 3D via the authenticated public communication channel 5.
In step S30, the low orbit satellite 3D calculates the exclusive OR of the calculation data α and the key _K4 stored in step S27, and decrypts the key _K3 of the low orbit satellite 3C.
In step S31, the low orbit satellite 3D stores the key _K3 of the low orbit satellite 3C.
In step S32, the low orbit satellite 3D notifies the low orbit satellite 3C of the completion of sharing the key _K3 .

Thereafter, the encryption key sharing system 1B can perform encrypted communication between the low orbit satellites 3C and 3D using the key _K3 as an encryption key.

[Action/Effect]
As described above, the encryption key sharing system 1B can share a large amount of encryption keys between the two low-orbit satellites 3C and 3D that are far apart. That is, the encryption key sharing system 1B can stably share encryption keys even between the low orbit satellites 3C and 3D, which have limited communication establishment conditions. As a result, the cryptographic key sharing system 1B can share cryptographic keys among many low orbit satellites, making it possible to perform large-capacity confidential communications on the satellite constellation.

(Third embodiment)
[Overview of encryption key sharing system]
With reference to FIG. 8, an overview of an encryption key sharing system 1C according to the third embodiment will be described.
As shown in FIG. 8, the encryption key sharing system 1C is a combination of the above-mentioned encryption key sharing subsystem 11B. Note that the low orbit satellite 3A is shared by the encryption key sharing subsystem 11B. Furthermore, in FIG. 8, illustration of the two geostationary satellites 2 (2A, 2B) is omitted to make the drawing easier to read.

That is, in the cryptographic key sharing system 1C, as shown in FIG. 8(a), the key _K1 is first shared between the low orbit satellite 3A and the ground station 3B via the geostationary satellite 2A, The key _K3 is shared between 3A and 3C via the geostationary satellite 2B. As a result, as shown in FIG. 8(b), the encryption key sharing system 1C uses the key _K3 to transmit desired transmission data S (for example, observation data by a sensor) from the low orbit satellite 3C to the low orbit satellite 3A. Send confidentially to Next, the encryption key sharing system 1C can secretly transmit the transmission data S from the low orbit satellite 3A to the ground station 3B using the key _K1 .

[Operation of encryption key sharing system]
The operation of the encryption key sharing system 1C will be explained with reference to FIGS. 9 and 10.
The processing in steps S20 and S21 is the same as that in FIG. 7, so a description thereof will be omitted.
The processing in steps S1 and S2 is the same as that in FIG. 5, so a description thereof will be omitted.

The processing in steps S22 to S32 is the same as that in FIG. 7, so a description thereof will be omitted. In addition, in FIG. 9 and FIG. 10, the calculation data obtained by the exclusive OR of the keys K ₃ and K ₄ is shown as α ₁ .
The processing in steps S3 to S13 is the same as that in FIG. 5, so a description thereof will be omitted. Note that the calculation data obtained by the exclusive OR of the keys K ₁ and K ₂ is shown as α ₂ .

In step S33, the low orbit satellite 3C obtains anonymized data _β1 by exclusive ORing the transmission data S and the key _K3 .
In step S34, the low orbit satellite 3C transmits the concealed data _β1 to the low orbit satellite 3A.

In step S35, the low orbit satellite 3A calculates the exclusive OR of the anonymized data β ₁ and the key K ₃ stored in step S31, and decrypts the transmission data S. Furthermore, the low orbit satellite 3A obtains anonymized data β ₂ by exclusive ORing the transmission data S and the key K ₁ .

In step S36, the low orbit satellite 3A transmits the concealed data _β2 to the ground station 3B.
In step S37, the ground station 3B calculates the exclusive OR of the anonymized data β ₂ and the key K ₁ stored in step S12, and decrypts the transmission data S.

[Action/Effect]
In this way, in the cryptographic key sharing system 1C, keys can be stably shared between the two low orbit satellites 3A and 3C and the ground station 3B, so a large amount of secrecy can be achieved between the satellite constellation and the ground station 3B. Communication becomes possible. As a result, the encryption key sharing system 1C can secretly transmit a large amount of sensor data on the observation/monitoring satellite to the ground station. That is, in the encryption key sharing system 1C, safe data communication can be performed to the ground station 3B by relaying data using encryption communication on the low orbit satellite constellation.

Furthermore, in the encryption key sharing system 1C, by using optical communication on the satellite constellation, data can be relayed at a higher speed than RF communication.
Furthermore, in the encryption key sharing system 1C, a highly available data downlink can be realized by performing RF communication that is less susceptible to weather conditions between the low orbit satellites 3A, 3C and the ground station 3B.

Note that in the encryption key sharing system 1C, the number of low orbit satellites can be increased to three or more. Further, although FIGS. 9 and 10 illustrate the geostationary satellites 2A and 2B of the cryptographic key sharing subsystem 11B, one geostationary satellite 2 may be shared.

(Fourth embodiment)
[Overview of encryption key sharing system]
An overview of the encryption key sharing system 1D according to the fourth embodiment will be described with reference to FIG. 11.
This cryptographic key sharing system 1D is a further application of the key sharing performed by the cryptographic key sharing system 1C shown in FIG. As shown in FIG. 11, the encryption key sharing system 1D includes a geostationary satellite 2, one first node (node 3 ₁ ), and second nodes (nodes 3 ₂ to 3 _n ) (where n is a natural number of 2 or more). In this embodiment, it is assumed that the node 3 ₁ is a low orbit satellite, the node 3 ₂ is a ground station, the node 3 ₃ is a maritime station, and the node 3 _n is an air station. Note that the configurations of the nodes 3 are assumed to be the same (see FIGS. 2 and 4).

A sea station is a node 3 located on the sea. For example, the marine station is a fixed station fixed at a predetermined location on the ocean, or a mobile station mounted on a moving ship or the like.
The aviation station is a node 3 mounted on an airplane or balloon.

As shown in FIG _. 11(a), the cryptographic key sharing system 1D uses line-of-sight communication quantum key distribution or physical layer encryption between the geostationary satellite 2 and the nodes _{3 1 to} 3 _n . Each of the keys K ₁ to K _n is shared.

Next, as shown in FIG. 11(b), the encryption key sharing system 1D generates a random number R and copies n-1 copies of the generated random number R on the geostationary satellite 2. Further, the encryption key sharing system 1D encrypts each random number R using keys K ₂ to K _n (for example, one-time pad encryption) and transmits it to the nodes 3 ₂ to 3 _n forming the group. Nodes 3 ₂ to 3 _n share random number R as a group key.

Next, as shown in FIG. 11(c), the encryption key sharing system 1D encrypts the transmission data S with the key _K1 (for example, one-time pad encryption) at the node ₃₁ , and sends it to the geostationary satellite 2. Send. Further, the cryptographic key sharing system 1D decrypts the received transmission data S on the geostationary satellite 2, anonymizes it using the group key R, and transmits it to the nodes 3 ₂ to 3 _n by multicast.

[Operation of encryption key sharing system]
The operation of the encryption key sharing system 1D will be explained with reference to FIGS. 12 and 13.
The processing in steps S40 to S43 and the processing in steps S44 to S47 are the same as steps S1 to S4 in FIG. 5, respectively, so their explanations will be omitted.

In step S48, the key management unit 21 of the geostationary satellite 2 generates a group key R using a random number.
In step S49, the key management unit 21 of the geostationary satellite 2 obtains calculation data α _n using the exclusive OR of the generated group key R and the key K _n of the node 3 _n .
In step S50, the geostationary satellite 2 transmits the calculation data α _n to the node 3 _n via the authenticated public communication channel 5.

In step S51, the node 3 _n calculates the exclusive OR of the calculation data α _n and the key K _n stored in step S47, and decrypts the group key R.
In step S52, the node _3n notifies the geostationary satellite 2 of the completion of sharing the group key R.

In step S53, the node ₃₁ conceals the transmission data S using the key _K1 using line-of-sight quantum key distribution or physical layer cryptography. Note that the transmission data S anonymized using the key _K1 is assumed to be anonymized data _β3 .
In step S54, the node ₃₁ transmits the anonymized data _β3 to the geostationary satellite 2 via the authenticated public communication channel 5.

In step S55, the key management unit 21 of the geostationary satellite 2 calculates the exclusive OR of the anonymized data β ₃ and the key K ₁ stored in step S43, and decrypts the transmission data S. Further, the key management unit 21 of the geostationary satellite 2 obtains anonymized data β ₄ by exclusive ORing the transmission data S and the group key R stored in step S48.

In step S56, the geostationary satellite 2 transmits the anonymized data β ₄ to the node 3 _n via the authenticated public communication channel 5.
In step S57, the node 3 _n calculates the exclusive OR of the calculation data α _n and the group key R, and decrypts the transmission data S.

[Action/Effect]
As described above, similarly to the first embodiment, the encryption key sharing system 1D has a long distance over which encryption keys can be shared, and can share a large amount of encryption keys. Furthermore, the encryption key sharing system 1D can safely share the transmission data S possessed by the node 3 ₁ among the nodes 3 ₂ to 3 _n .

(Fifth embodiment)
[Overview of encryption key sharing system]
Referring to FIG. 14, an encryption key sharing system 1E according to the fifth embodiment will be described.
As shown in FIG. 14, the encryption key sharing system 1E realizes key sharing on a global scale by relaying three geostationary satellites 2 (2A, 2C, 2B). Specifically, the cryptographic key sharing system 1E uses a plurality of geostationary satellites 2A, 2C, and 22B to relay between the ground stations 3E and 3F using line-of-sight quantum key distribution or physical layer cryptography, and transmits data between the geostationary satellites 2A to 2C. However, by sharing the keys K ₂ and K ₃ for transmitting and receiving the key K ₁ in secret, the key K ₁ is decrypted at the ground station 3F.

Communication between ground stations 3E and 3F, which are located on opposite sides of Earth E, is required via submarine optical cables, but because they are equipped with repeater amplifiers, the quantum state of light is destroyed and quantum key distribution is not possible. doesn't work. Additionally, if quantum repeaters can be realized, it will be possible to share keys via submarine optical cables, but it is unclear when quantum repeaters will be put into practical use.

Therefore, the encryption key sharing system 1E further arranges a relaying geostationary satellite 2C, and as in the third embodiment, by combining the two encryption key sharing systems 1, key sharing is realized on a global scale. . As shown in FIG. 14, the encryption key sharing system 1E includes geostationary satellites 2A to 2C and ground stations 3E and 3F.

[Configuration of encryption key sharing system]
The configuration of the encryption key sharing system 1E will be described with reference to FIG. 15. In addition, in FIG. 15, a set of the relay geostationary satellite 2C and the geostationary satellites 2A and 2B is extracted as the encryption key sharing subsystem 12. Note that the configurations of the ground stations 3E and 3F are similar to the ground station 3B in FIG. 4, and therefore the description thereof will be omitted.

<Geostationary satellite for relay>
As shown in FIG. 15, the geostationary satellite 2C has the same configuration as the ground station 3B in FIG. 4, and includes a line-of-sight communication section 30E, a key management section 31B, and a data communication section 32.
Further, the line-of-sight communication section 30E includes a transmission optical section 300, a key distillation section 310B, and a communication channel state monitoring section 320E.

The communication path state monitoring section 320E is a general one that irradiates the communication path state monitoring section 220 with the probe light 41. Further, the communication channel state monitoring unit 320E measures the state of the line-of-sight communication channel 4 by observing the probe light 41E emitted by the communication channel state monitoring unit 220E.

<Geostationary satellite>
As shown in FIG. 15, the geostationary satellites 2A and 2B have the same configuration as the geostationary satellite 2 in FIG. 2, and include a line-of-sight communication section 20E, a key management section 21, and a data communication section 22.
Further, the line-of-sight communication section 30E includes a reception optical section 200, a key distillation section 210, and a communication channel state monitoring section 220E.

The communication channel state monitoring section 220E is a general one that irradiates the communication channel state monitoring section 320E with the probe light 41E. Furthermore, the communication channel state monitoring unit 220E measures the state of the line-of-sight communication channel 4 by observing the probe light 41 irradiated by the communication channel state monitoring unit 220E.

[Operation of encryption key sharing system]
The operation of the encryption key sharing system 1E will be explained with reference to FIG. 16.
As shown in FIG. 16, in step S60, the geostationary satellite 2C transmits random number bits to the geostationary satellite 2A via the line-of-sight channel 4.
In step S61, the geostationary satellites 2A and 2C generate and share a safe key _K2 through key distillation processing.
In step S62, the geostationary satellite 2A stores the key _K2 .
In step S63, the geostationary satellite 2C stores the key _K2 .

In step S64, the ground station 3F transmits random number bits to the geostationary satellite 2B via the line-of-sight channel 4.
In step S65, the geostationary satellite 2B and the ground station 3F generate and share a secure key _K4 through key distillation processing.
In step S66, the geostationary satellite 2B stores the key _K4 .
In step S67, the ground station 3F stores the key _K4 .

The processing in steps S68 to S71 is similar to the processing in steps S64 to S67, so the description thereof will be omitted. Note that the encryption key shared between the geostationary satellite 2A and the ground station 3E is key _K1 .
The processing in steps S72 to S75 is similar to the processing in steps S60 to S62, so the description thereof will be omitted. Note that the encryption key shared between the geostationary satellites 2B and 2C is key _K3 .

In step S76, the geostationary satellite 2A obtains the exclusive OR of the keys K ₁ and K ₂ stored in steps S62 and S71 as calculation data K _A.
In step S77, the geostationary satellite 2A transmits the calculation data _KA to the geostationary satellite 2C via the authenticated public communication channel 5.

In step S78, the geostationary satellite 2C decrypts the key _K1 of the ground station 3E by calculating the exclusive OR of the calculation data _KA and the key _K2 stored in step S63. Furthermore, the geostationary satellite 2C obtains the exclusive OR of the key _K1 and the key _K3 stored in step S74 as calculation data _KB .
In step S79, the geostationary satellite 2C transmits the calculation data _KB to the geostationary satellite 2B via the authenticated public communication channel 5.

In step S80, the geostationary satellite 2B decrypts the key _K1 of the ground station 3E by calculating the exclusive OR of the calculation data _KB and the key _K3 stored in step S75. Furthermore, the geostationary satellite 2C obtains the exclusive OR of the key _K1 and the key _K4 stored in step S66 as calculation data _K.sub.C.
In step S81, the geostationary satellite 2B transmits the calculation data _KC to the ground station 3F via the authenticated public communication channel 5.

In step S82, the ground station 3F decrypts the key _K1 of the ground station 3E by calculating the exclusive OR of the calculation data K _C and the key _K4 stored in step S67.
In step S83, the ground station 3F stores the key _K1 .
In step S84, the ground station 3F notifies the ground station 3E of completion of sharing the key _K1 .

[Action/Effect]
As described above, in the cryptographic key sharing system 1E, the keys K ₂ to K ₄ are used to anonymize the key K ₁ of the ground station 3E and relayed in three hops to the ground station located on the opposite side of the earth E. Can transmit up to station 3F. Thereby, in the cryptographic key sharing system 1E, the key _K1 can be shared between the ground stations 3E and 3F. Compared to the case where cryptographic keys are relayed using low-orbit satellites, the cryptographic key sharing system 1E can distribute a large amount of keys much more stably even between the ground stations 3E and 3F on the opposite side of the earth E.

The encryption key sharing systems 1 to 1E according to each embodiment are particularly effective on a global network consisting of a satellite constellation made up of satellites in various orbits, and ground stations, maritime stations, aviation stations, etc. . By applying the cryptographic key sharing systems 1 to 1D according to each embodiment to each satellite main body, the security of the TTC (Telemetry, Tracking & Control) of the satellite main body, observation data from space, data stored in space, and data transmitted through space can be improved. Key sharing for secure communications can be flexibly set according to the security level even after launch. Furthermore, by using geostationary satellites that centrally manage functions, it is possible to supervise TTC of satellite constellations made up of satellites in various orbits and key sharing for secure confidential communication of various data.

Furthermore, the observation data from space may include planetary observation data and space situation monitoring data in addition to earth observation data. Further, the various types of data subject to the safe confidential communication may include observation data from space, data stored in space, and data transmitted via space.

1 Encryption key sharing system 2 Geostationary satellite 3 Node 3A Low orbit satellite 3B Ground station 4 Line-of-sight communication channel 5 Public communication channel with authentication 20 Line-of-sight communication section 21 Key management section 22 Data communication section 30 Line-of-sight communication section 31 Key management section 32 Data communication Department

Claims (6)

A cryptographic key sharing system for sharing cryptographic keys between a first node and a second node by line-of-sight quantum key distribution or physical layer cryptography relayed by a geostationary satellite, the system comprising:
The geostationary satellite shares a first encryption key and a second encryption key between the first node and the second node, respectively, by the line-of-sight quantum key distribution or the physical layer encryption, and and a second encryption key, and transmitting the calculation result to the second node via an authenticated public communication channel,
The encryption key sharing system, wherein the second node decrypts the first encryption key by calculating an exclusive OR of the calculation result and the second encryption key. 2. The encryption key sharing system according to claim 1, wherein each of the first node and the second node is one or more of a ground station, a low orbit satellite, a maritime station, or an aviation station. The communication between the first node and the second node is relayed by the plurality of geostationary satellites using the line-of-sight communication quantum key distribution or the physical layer encryption, and the first encryption key is concealed and transmitted and received between the geostationary satellites. 3. The cryptographic key sharing system according to claim 1, wherein the second node decrypts the first cryptographic key by sharing a cryptographic key for decrypting the first cryptographic key. The first node conceals the transmission data using the encryption key shared with the geostationary satellite by the line-of-sight quantum key distribution or the physical layer encryption, and transmits the data to the geostationary satellite;
The geostationary satellite decrypts the transmission data using the encryption key, generates a group key with a random number, anonymizes the decrypted transmission data with the group key, and transmits the data via the authenticated public communication channel. , to each second node constituting the group,
The geostationary satellite conceals the group key using the second encryption key shared with each of the second nodes, and transmits the concealed group key to the public communication channel with authentication. to each second node,
Each of the second nodes decrypts the group key using an exclusive OR of the anonymized group key and the second encryption key, and combines the decrypted group key with the anonymized transmission data. 3. The cryptographic key sharing system according to claim 1, wherein the transmitted data is decrypted using an exclusive OR of the following. The geostationary satellite is
a line-of-sight communication unit that shares the first encryption key and the second encryption key by the line-of-sight communication quantum key distribution or the physical layer encryption;
a key management unit that obtains calculation data for an exclusive OR of the first encryption key and the second encryption key;
a data communication unit that transmits the calculation data obtained by the key management unit to the second node via the authenticated public communication channel;
The cryptographic key sharing system according to claim 1 or claim 2, comprising: The second node is
a line-of-sight communication unit that shares the second encryption key with the geostationary satellite by line-of-sight communication quantum key distribution or physical layer encryption;
a data communication unit that receives calculation data of an exclusive OR of the first encryption key and the second encryption key from the geostationary satellite via the authenticated public communication channel;
a key management unit that decrypts the first encryption key using an exclusive OR of the calculation data received by the data communication unit and the second encryption key;
The cryptographic key sharing system according to claim 1 or claim 2, comprising:

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