JP2019220762A - Secret key sharing system and secret key sharing method - Google Patents

Abstract

To provide a secret key sharing system and a secret key sharing method that share a secret key between a sender device and a normal receiver device by using optical space communication.SOLUTION: A sender device 11 generates a secret key for optical space communication and RF band communication and distributes it to a normal receiver device 14 by optical space communication and RF band communication. The sender device receives information on a secret key selected by the normal receiver device 14, generates an optical space communication secret key and RF band communication secret key, generates a final secret key to be shared with the normal receiver device 14 on the basis of a common random number sequence included in the generated optical space communication secret key and RF band communication secret key, and shares it with the normal receiver device 14.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a secret key sharing system and a secret key sharing method for sharing a secret key between a sender device and a legitimate recipient device using optical space communication.

  The development of quantum computers in recent years is being promoted not only by Japan but also by overseas research institutions and the like, and it is expected that quantum computers capable of handling large-capacity qubits will be realized in the future. Although this large-capacity qubit computer can be realized in principle, it is said that it takes an enormous amount of processing time. Current encryption methods require security for the discrete logarithm problem and the mathematical difficulties of prime factorization. Even if it is included in the encryption, it may be broken. Therefore, a threat such as eavesdropping of the confidential information by a third party (an eavesdropper) occurs. Furthermore, since the performance of computers has been improving year by year, security of security technologies such as encryption technologies may be reduced by advanced computing capabilities and decryption algorithms.

  As a method of encryption against the above-mentioned threats, eavesdropping by a third party, and the like, quantum key distribution (QKD: Quantum Key Distribution) has been proposed as a technology that can safely share an encryption key. This QKD is a quantum communication method for decoding an encoded communication resource using a quantum state using a quantum communication channel. The sender encodes information input by an encoder that performs QKD using a quantum effect, and transmits the encoded information to a communication channel as a communication resource. The receiving party can receive the communication resources transmitted to the communication path and obtain the target information by decoding the communication resources with the decoder (for example, see Patent Document 1). With QKD, it is possible to share information-theoretically secure random numbers between two remote parties.

  However, in the current fiber-based QKD, a strong limit is imposed on the distance and speed at which a key can be provided. Therefore, when the transmission distance is about 50 to 100 km, the key generation rate is about several k to 1 Mbps. For this reason, a QKD experiment using a satellite has been conducted with the aim of extending the key distribution distance of QKD. For example, in another country (China), there have been reports of successful key generation between a satellite and a ground station that are more than 1200 km away, but satellite-based QKD limits the time during which satellites can track satellites. . Further, since it is difficult to increase the speed of the QKD device mounted on a satellite, the key generation rate is at most about 1 kbps. The key security index value, which is a security parameter, is also set at a lower value than that used in terrestrial fiber-based QKD devices. Also, the information theory based on security is not the latest, and there is room for improvement in key security.

  The security of the key is information-theoretically secure, and there is a need for a technology capable of sharing a secure key across Japan or between continents. Even in the case where the capability of an eavesdropper assumed in QKD can be limited, research on physical layer encryption that enables secure key generation for information processing has been actively conducted in recent years.

  In these studies, for example, in the wire tap model, the receiving / retransmitting attack assumed in QKD is not assumed. Therefore, if it is possible to know what signal has passed to the eavesdropper by using the physical layer encryption, a secure key can be generated by using the public communication path together. In addition, if the unavoidable noise source can be set to the eavesdropper, the secret key sharing protocol that enables secure key generation due to the difference in signal-to-noise ratio between the normal transmitter and receiver devices will provide better communication performance than QKD. Could be realized.

  For example, a virtual eavesdropper having a strong receiving capability is installed near a legitimate receiver device on the line-of-sight communication path of optical communication, and the maximum amount of information leaked to a true eavesdropper is regarded as a safe key generation. (For example, see Non-Patent Document 1 and Non-Patent Document 2). In these proposals and demonstrations, lectures will be given on key security under the assumption that there are no eavesdroppers on the line of sight while monitoring the line with telescopes and cameras, etc. are doing. However, the ability of existing cameras to monitor the line-of-sight communication path can only identify objects of about 10 cm in size due to the fluctuation of the image due to the atmosphere, and even if space debris monitoring technology is introduced, it will be about 10 cm. This is a level at which an object (such as a small photodetector) can be identified (for example, see Non-Patent Document 3).

JP 2004-104345 A

M.Fujiwara, T.Ito, M.Kitamura, H.Endo, M.Toyoshima, H.Takanaka, Y.Takayama, R.Shimizu, M.Takeoka, and M.Sasaki, `` Secret key agreement demonstration over 7.8 km free -space optical channel '', International Conference on Quantum Communication, Measurement and Computing 2016, July 2016 H.Endo, M.Fujiwara, M.Kitamura, T.Ito, M.Toyoshima, Y.Takayama, H.Takenaka, R.Shimizu, N.Laurenti, G.Villoresi, T.Aoki, and M.Sasaki, `` Free-space optical channel estimation for physical layer security, Opt.Express, vol.24, no.8, August 2016, p.8940-8955 Ministry of Education, Culture, Sports, Science and Technology, Research and Development Bureau Counselor (in charge of aerospace policy), [online], "Information on the fall of the U.S. satellite" UARS "", September 2011, [Searched on June 6, 2018], Internet , <URL: http://www.mext.go.jp/a_menu/kaihatu/satel lite / detail / 1311417.htm>

  By the way, in the QKD technology including the above-mentioned Patent Document 1 and Non-Patent Documents 1 to 3, it is assumed that an eavesdropper on the line-of-sight communication path can perform any action such as using a quantum memory or a quantum computer. For this reason, a strong restriction must be imposed on the key generation speed and the service distance. Also, even if an object having a size of 10 cm or less (such as a small detector) is installed by an eavesdropper in the line of sight communication path, it cannot be identified, so it is difficult to eliminate the danger or risk from eavesdropping. .

  On the other hand, in the RF band (RF: Radio Frequency), considering the implementation of physical layer encryption using an RF band lower than 750 MHz, the antenna size must be at least as large as a wavelength of 10 cm. Therefore, it is difficult to reduce the size of the detection system as described above. If a detection system is installed in the line-of-sight communication path by an eavesdropper, an antenna having a size of at least 10 cm is required. However, in RF band communication using an antenna, band limitation and directivity are inferior to those using communication using light.

  Therefore, the present invention has been devised in view of the above-described problems, and has as its object to provide a secret key sharing system and a secret key sharing system capable of performing key sharing more securely on a line-of-sight communication path. It is to provide a method.

  The secret key sharing system according to the first invention is a secret key sharing system for sharing a secret key between a sender device and a legitimate receiver device arranged in a line-of-sight communication path, wherein the sender device includes: A key distribution unit that generates a secret key for optical space communication and RF band communication by modulating a registered random number sequence, and distributes the generated secret key to an authorized receiver device via the optical space communication and RF band communication. And a communication secret for receiving information about the secret key selected by the authorized receiver device based on the distribution of the key distribution unit, and generating an optical space communication secret key and an RF band communication secret key based on the received information. Based on a common random number sequence included in the optical space communication secret key and the RF band communication secret key generated by the key generation unit and the communication secret key generation unit, a final secret key to be shared with the authorized receiver is determined. Generate final secret key to generate The authorized receiver device has a transmission unit that receives the secret key distributed via the optical space communication and the RF band communication by the key distribution unit, selects the secret key, and transmits the selected private key to the transmitter device. It is characterized by the following.

  In the secret key sharing system according to the second invention, in the first invention, the final secret key generation unit matches the final secret key with the optical space communication secret key and the RF band communication secret key formed by a random number sequence of the same length. It is characterized in that it is generated by causing

  A secret key sharing system according to a third aspect of the present invention is a secret key sharing system for sharing a secret key between a sender device and an authorized receiver device arranged in a line-of-sight communication path, wherein the sender device is a registered device. The generated random number sequence is divided into a plurality of pieces, and a plurality of secret keys for optical space communication in which the divided random number strings are respectively superimposed are generated, and the normal receiver device is set in advance at the center of the beam for the optical space communication. A key distribution unit that distributes a plurality of secret keys by beam wandering so as to include the center of the beam; and a plurality of secret keys selected by the authorized receiver device based on distribution by the key distribution unit. A communication secret key generation unit that generates an optical space communication secret key; and a transmitter and the regular reception unit based on a common random number sequence included in the optical space communication secret key generated by the communication secret key generation unit. And a final secret key generation unit that generates a final secret key to be shared by the devices. The authorized receiver device receives the secret key distributed via the optical space communication by the key distribution unit and selects the secret key. And a transmitting unit for transmitting the data to the transmitter device.

  The secret key sharing system according to a fourth invention is characterized in that, in the third invention, the range of beam wandering is set and distributed based on the assumed position of the leakage information estimation receiver and the position of the eavesdropper. And

  A secret key sharing method according to a fifth aspect of the present invention is a secret key sharing method for sharing a secret key between a sender device and a legitimate receiver device arranged in a line-of-sight communication channel, wherein a registered random number sequence is A key distribution step of generating a secret key for the spatial optical communication and the RF band communication by modulating, and distributing the generated secret key from the sender device to the authorized receiver device via the spatial light communication and the RF band communication; A transmitting step of receiving the secret key distributed through the optical space communication and the RF band communication by the key distribution step in the authorized receiver device, selecting the secret key, and transmitting the selected secret key to the transmitter device; The transmitter device receives the information related to the secret key, and generates the optical space communication secret key and the RF band communication secret key based on the received contents. A final secret key generating step of generating a final secret key to be shared between the sender device and the authorized receiver device based on the common random number sequence included in the optical space communication secret key and the RF band communication secret key. It is characterized by having.

  A secret key sharing method according to a sixth aspect of the present invention is a secret key sharing method for sharing a secret key between a sender device and a legitimate receiver device arranged in a line-of-sight communication path. The generated random number sequence is divided into a plurality of pieces, and a plurality of secret keys for optical space communication in which the divided random number strings are respectively superimposed are generated, and the normal receiver device is set in advance at the center of the beam for the optical space communication. A key distribution step of distributing a plurality of secret keys by beam wandering so as to include the center of the beam, and a reception of the secret key distributed via optical space communication in the key distribution step in the authorized receiver device And transmitting a plurality of secret keys selected by the authorized receiver device to the transmitter device to generate an optical space communication secret key. Based on a common random number sequence included in the optical space communication secret key generated in the communication secret key generation step and the communication secret key generation step, a final secret key to be generated between the sender device and the authorized receiver device is generated. Secret key generation step.

  According to the first invention to the sixth invention, space communication and RF band communication are used for quantum cryptography communication between the sender device and the authorized receiver device. For this reason, a secret key can be shared even in RF communication at a frequency lower than 750 MHz, which cannot detect a substance of 10 cm or less in space optical communication, but cannot easily receive an antenna of 10 cm or less in RF band communication. As a result, the result of coding one key with another key is used as the final key common to the sender device and the legitimate receiver device, so that information to an eavesdropper associated with the wide beam spread angle of the RF band communication is provided. It is possible to securely implement a common secret key, which can eliminate a threat caused by the presence of an eavesdropper on a communication path in leakage and optical space communication.

  In particular, according to the second invention, the final secret key is generated by matching the optical space communication secret key and the high frequency band communication secret key formed of a random number sequence of the same length. For this reason, the receiving ability of an eavesdropper can be limited as compared with channel coding and secret key sharing using only optical space communication or only RF band communication. As a result, even if an eavesdropper is present in the communication path, secure key sharing can be performed between the sender device and the authorized receiver device.

  In particular, according to the third aspect, by changing the central axis of the light beam in the vicinity of the normal receiver device and transmitting the light beam, the light beam from the transmitter device becomes plural, and the range of the light beam is widened as a whole. For this reason, it is assumed that the maximum amount of information leaked to an eavesdropper is provided, and secure key generation and sharing can be performed between the sender device and the authorized receiver device. When the spread range is large, it is divided into a plurality, so that the light beam spread angle can be effectively narrowed, and the common use of the secret key can be implemented safely.

  In particular, according to the fourth aspect, the message is divided and transmitted according to the number of times of beam wandering. Therefore, even if only one eavesdropper eavesdrops, the eavesdropper does not know the whole image. As a result, even if there is an eavesdropper in the communication path, key sharing can be realized safely and at high speed. Further, information leakage due to the light beam divergence angle of light due to optical space communication can be suppressed. As a result, it becomes a very powerful method for realizing the physical layer encryption in the sender device and the authorized receiver device, and the secret key can be shared in common.

  In particular, according to the fifth aspect, optical space communication and RF band communication are used for quantum cryptography communication between the sender device and the authorized receiver device. For this reason, a secret key can be shared even in RF communication at a frequency lower than 750 MHz, which cannot detect a substance of 10 cm or less in optical space communication, but cannot easily receive an antenna of 10 cm or less in RF band communication. Thus, by using the result of coding one key with another key as the final key, information leakage to an eavesdropper due to the wide light beam divergence angle of the RF band communication and the communication path in the optical space communication Threats caused by the presence of an eavesdropper can be eliminated, and the secret key can be shared in common.

  In particular, according to the sixth aspect, by changing the central axis of the light beam near the regular receiver device and transmitting the light beam, a plurality of light beams are transmitted from the transmitter device, and the range of the light beam is broadened as a whole. For this reason, it is assumed that the maximum amount of information leaked to an eavesdropper is provided, and secure key generation becomes possible. When the spread range is large, it is divided into a plurality of parts, so that the light beam spread angle can be effectively narrowed, and the secret key can be securely shared between the transmitter device and the authorized receiver device.

FIG. 1 is a schematic diagram showing an example of a secret key sharing system to which the present invention is applied. FIG. 2 is a block diagram showing an example of the configuration of the satellite 1 of the secret key sharing system to which the present invention is applied. FIG. 3 is a block diagram illustrating an example of the secret key sharing system according to the first embodiment. FIG. 4 is a schematic diagram illustrating an example of an operation of sharing a secret key in the first embodiment. FIG. 5 is a schematic diagram illustrating an example of a secret key sharing system according to the second embodiment. FIG. 6 is a schematic diagram illustrating an example of the operation of secret key sharing in the second embodiment. FIG. 7 is a schematic diagram illustrating an example of an operation of sharing a secret key in the second embodiment.

  Hereinafter, an example of a secret key sharing system according to an embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 is a schematic diagram showing an example of a secret key sharing system 10 according to the present embodiment.

  As shown in FIG. 1, the secret key sharing system 10 of this embodiment is based on quantum key distribution using a satellite 1, two ground stations 2, and an antenna 3, and is capable of sharing a secret key on a global scale. Become. The satellite 1 is a sender device 11, and the ground station 2 and the antenna 3 are regular receiver devices 14. The authorized receiver device 14 is a device on the other side where the sender device 11 truly desires to share a secret key.

  The legitimate receiver device 14 performs processing such as bit error and error correction according to the reception status, and selects the secret key distributed from the sender device 11. The ground station 2 in the regular receiver device 14 performs optical space communication from the satellite 1 using a telescope, for example. Further, the antenna 3 of the regular receiver device 14 performs RF band communication with the satellite 1 using RF band radio waves.

  FIG. 2 is a block diagram showing an example of the configuration of the satellite 1 of the secret key sharing system to which the present invention is applied.

  The satellite 1 includes a key distribution unit 4, a communication secret key generation unit 5, and a final secret key generation unit 6, as shown in FIG. The key distribution unit 4 includes an optical space communication key distribution unit 41 and an RF band communication key distribution unit 42. The key distribution unit 4 modulates a random number sequence to generate each secret key in the optical space communication key distribution unit 41 and the RF band communication key distribution unit 42, and transmits the generated secret key to the optical space communication and the RF The data is distributed to the ground station 2 and the antenna 3 via the band communication.

  The optical space communication key distribution unit 41 generates a random number sequence modulated by a physical random number generator mounted on the satellite 1. This random number sequence may be registered in advance. The optical space communication key distribution unit 41 distributes the generated random number sequence to the ground station 2 by optical space communication using the quantum effect. This optical space communication may be transmitted, for example, by a light beam method provided in the satellite 1. In this case, the intensity of the light beam, the range of the light beam reaching the ground due to the aperture, and the like may be determined. Note that the light beam may be distributed while the position of the ground station 2 is set to be the center of the light beam, for example.

  The RF band communication key distribution unit 42 distributes the random number sequence modulated by the physical random number generator to the antenna 3 by RF band communication. The communication secret key generation unit 5 receives the secret key selected by the authorized receiver device 14 based on the distribution of the key distribution unit 4, and matches the secret key.

  The communication secret key generation unit 5 receives information on each secret key selected by the authorized receiver device 14. The communication secret key generation unit 5 matches the selection result based on the information about the secret key. The communication secret key generation unit 5 generates the selected optical space communication secret key and RF band communication secret key.

  The final secret key generation unit 6 should be shared with the authorized receiver device 14 based on the common random number sequence included in the optical space communication secret key and the RF band communication secret key generated by the communication secret key generation unit 5. Generate a final secret key. For example, the final secret key generation unit 6 may be provided in the authorized receiver device 14.

  FIG. 3 is a diagram showing an overall configuration when an eavesdropper device 15 intrudes in a secret key sharing system to which the present invention is applied. In FIG. 3, there is a case where there are a plurality of ground stations 2 distributed from the transmitter device 11 (satellite 1) corresponding to the satellite 1 described above, one of which is a legitimate receiver device 14 and the other is an eavesdropper device 15. It is.

  The regular receiver device 14 (the ground station 2 and the antenna 3) performs optical spatial communication with the transmitter device 11 (the satellite 1) via the main communication path 12. The eavesdropper device 15 has a configuration corresponding to at least the ground station 2 and may further include a configuration corresponding to the antenna 3. The eavesdropper device 15 is a device that does not want the sender device 11 to share a secret key. The eavesdropper device 15 has a purpose of eavesdropping by optical spatial communication from the sender device 11 via the eavesdropper communication path 13. Or interception of RF band communication.

  Next, the operation of the secret key sharing system 10 to which the present invention is applied will be described.

  The satellite 1 modulates a true random number generated by an on-board physical random number generator (not shown) into a quantum state of light, and distributes it to the ground station 2 by optical space communication. The satellite 1 similarly modulates the true random number, and transmits it to the antenna 3 by RF band communication. It is to be noted that the physical random number generator is held in common with the regular receiver device 14 before the launch of the satellite 1.

  The ground station 2 and the antenna 3 correct the deterioration of the information distributed by the optical space communication and the RF band communication distributed from the satellite 1 based on the intrinsic random numbers already possessed. This correction processing is, for example, bit error, error correction, and the like. As a result, the satellite 1 can generate the optical space communication secret key and the RF band communication secret key based on information (such as correction information) on the secret key transmitted from the authorized receiver device 14 and hold the common secret key. be able to.

  The satellite 1 receives the selection result information from the ground station 2 and the antenna 3 through the optical space communication and the RF band communication. The communication secret key generation unit 5 in the satellite 1 matches the random number sequence distributed by the optical space communication and the RF band communication based on the selection result information. Then, an optical space communication secret key and an RF band communication secret key are generated based on the result of the matching.

  The final secret key generation unit 6 prepares the same number of bits from the optical space communication secret key and the RF band communication secret key generated at different wavelengths according to the above-described processing. As shown in FIG. 4, the final secret key generation unit 6 calculates, for example, an exclusive OR from the prepared number of bits for the optical space communication secret key and the RF band communication secret key, and determines the calculation result as the final secret key. I do.

  The final secret key is calculated by, for example, an exclusive OR operation with respect to each bit in both the optical space communication secret key (Key1) and the RF band communication secret key (Key2). As a result, a common random number is generated as the final secret key, and the common random number is shared by the sender device 11 and the authorized receiver device 14.

  As described above, according to the first embodiment, the final secret key is generated between the sender device 11 and the authorized receiver device 14 based on the selection result of the separate communication using the spatial optical communication and the RF band communication. I do. Therefore, even if one of the optical space communication and the RF band communication is intercepted via the eavesdropper device 15, the final secret key cannot be reproduced from the eavesdropper device 15. For this reason, the authorized receiver device 14 can more securely share the final secret key without being intercepted by the eavesdropper device 15.

Second Embodiment Hereinafter, a second embodiment of the secret key sharing system 10 to which the present invention is applied will be described. In the second embodiment, the same components and members as those in the above-described first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.

  In the second embodiment, as shown in FIG. 5, only the satellite 1 is used as the transmitter device 11, and only the ground station 2 is used as the normal receiver device 14. Note that a configuration for generating the final key is installed in the authorized receiver device 14 in advance.

  The satellite 1 serving as the sender device 11 modulates a true random number generated by an on-board physical random number generator (not shown) into a quantum state of light, and a regular receiver device serving as the ground station 2 by optical space communication. 14 The authorized receiver device 14 generates a final secret key to be shared with the sender device 11 based on the secret key distributed through the optical space communication.

  Hereinafter, the optical space communication method according to the second embodiment will be described in detail.

  The sender device 11 presets the center of the light beam of the space optical communication to the authorized receiver device 14. FIG. 6 shows a setting example of the light beam. When setting the light beam, the center of the light beam of the optical space communication, the position of the authorized receiver device 14, and the position of the eavesdropper device 15 are considered. Incidentally, the eavesdropping device 15 may be set to a pseudo, so-called fictitious one.

  In the following example, the detection capability of the eavesdropper device 15 is assumed to be equivalent to that of the authorized receiver device 14. In addition, the eavesdropper device 15 enables reception of one light beam from the transmitter device 11 at the same energy density as that of the eavesdropper device 15, and that the other light beams are separated by 1σ or more. Assume.

  Under this assumption, the range of the beam wandering is set to include the center of the light beam of the optical space communication. The light beams 30 to 32 of the beam wandering in FIG. 6 are examples in which the center of the light beam of the optical space communication is set to include the center while being set to the regular receiver device 14. The light beams 30 to 32 are set so as not to completely overlap each other, and the centers thereof are set to be shifted from the regular receiver device 14.

  In the second embodiment, the sender device 11 divides the actually registered random number sequence into a plurality. Then, a plurality of secret keys in which the divided random number sequences are superimposed are generated. The key distribution unit 4 in the sender device 11 distributes the secret key based on the divided random number sequence to the authorized receiver device 14 by superimposing the secret key on each light beam to be beam-wandered.

  For example, as shown in FIG. 7, when a random number sequence is divided into three, a divided secret key A, a divided secret key B, and a divided secret key C, at least three light beams to be beam-wandered are set. The secret key is superimposed on each light beam and distributed to the authorized receiver device 14. In the example of FIG. 7, the divided secret key A is distributed on the light beam 30, the divided secret key B is distributed on the light beam 31, and the divided secret key C is distributed on the light beam 32.

  The divided secret key A, the divided secret key B, and the divided secret key C are used by the transmitter device 11 and the legitimate receiver device 14 in the optical space communication based on the difference between the error rate of each light beam and the estimated value of the leakage information amount. The key length of the secret key may be different. For this reason, the legitimate receiver device 14 that has received these beam-wandered light beams, for example, among the received divided secret keys A, B, and C, for example, has the smallest key length of the secret key. Is set as the key length obtained with each secret key, and processing for discarding keys longer than that is performed.

  Then, the authorized receiver device 14 extracts a common random number from each exclusive OR based on the divided secret key A, the divided secret key B, and the divided secret key C. Then, the extracted common random number is wandered via the optical space communication and used as the final secret key shared by the authorized receiver device 14.

  As shown in FIG. 6, the maximum approach distance in the actual eavesdropping device 15 is estimated by detecting the amount of leaked information through the leaky information estimating required receiver, which is set in a pseudo manner, centering on the legitimate receiver device 14. be able to. In order to generate the final secret key, it is necessary to accurately obtain all of the divided secret keys with high strength. That is, if even one of the divided secret keys is missing, the final secret key cannot be generated.

  In order for the eavesdropper device 15 to actually receive all of the beam-wandered light beams, it is necessary to approach the same position as the regular receiver device 14 or to a position very close to the same, but in practice this is quite difficult difficult. For this reason, the reception of the light beam by the eavesdropper device 15 is incomplete, and it is practically difficult to obtain the final secret key.

  Therefore, the authorized recipient device 14 can more securely share the final secret key without being intercepted by the eavesdropper device 15.

  Note that the key distribution unit 4 may perform beam wandering on the actually delivered light beam after narrowing the beam diameter. This makes it possible to extremely efficiently reduce information leakage due to the spread of the beam.

  The secret key sharing method for sharing a secret key between a sender device and a legitimate receiver device arranged in a line-of-sight communication path according to the present embodiment includes a key distribution step in the secret key sharing system 10 described above; By having a transmission step, a communication secret key generation step, and a final secret key generation step, secret key sharing is possible even in RF communication at a frequency lower than 750 MHz, which cannot be easily received by an antenna of 10 cm or less in RF band communication. It becomes.

  Thus, by using the result of coding one key with another key as the final key, information leakage to an eavesdropper due to the wide light beam divergence angle of the RF band communication and the communication path in the optical space communication Threats caused by the presence of an eavesdropper can be eliminated, and the secret key can be shared in common.

  Although the embodiments of the present invention have been described, each embodiment is presented by way of example and is not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

1: satellite 2: ground station 3: antenna 4: key distribution unit 5: communication secret key generation unit 6: final secret key generation unit 10: secret key sharing system 11: sender device 12: main communication path 13: eavesdropper communication Road 14: Normal receiver device 15: Eavesdropper devices 30, 31, 32: Light beam 41: Optical space communication key distribution unit 42: RF band communication key distribution units A to C: Divided secret key

Claims (6)

A secret key sharing system for sharing a secret key between a sender device and an authorized receiver device arranged in a line-of-sight communication path,
The sender device,
A key distribution unit that transmits the random number sequence using the optical spatial communication and the RF band communication, generates a secret key, and distributes the generated secret key to the authorized receiver device through the optical spatial communication and the RF band communication; ,
A communication secret key for receiving information on the secret key selected by the authorized receiver device based on the distribution of the key distribution unit and generating an optical space communication secret key and an RF band communication secret key based on the received content; A generating unit;
Based on a common random number sequence included in the optical space communication secret key and RF band communication secret key generated by the communication secret key generation unit, a final secret key to be shared with the authorized receiver is generated. A secret key generation unit,
The legitimate recipient device,
A transmitting unit that receives the secret key distributed via the optical space communication and the RF band communication by the key distribution unit, selects the secret key, and transmits the selected private key to the sender device;
A secret key sharing system characterized by the following. The final secret key generation unit generates the final secret key by matching the optical space communication secret key and the RF band communication secret key formed of a random number sequence of the same length,
The secret key sharing system according to claim 1, wherein: A secret key sharing system for sharing a secret key between a sender device and a legitimate receiver device arranged in a line-of-sight communication path,
The sender device,
The random number sequence is divided into a plurality, and a plurality of optical space communication secret keys are generated by superimposing the divided random number sequences, and the legitimate receiver device is set in advance at the center of the beam of the optical space communication. Having a key distribution unit that distributes the plurality of secret keys by beam wandering to include the center of the beam,
The legitimate recipient device,
A final secret key generation unit that generates a final secret key to be shared with the sender device based on a secret key included in each light beam distributed via the optical space communication by the key distribution unit. Secret key sharing system. The key distribution unit sets and distributes the beam wandering range based on the assumed position of the leakage information estimation receiver and the position of the eavesdropper,
The secret key sharing system according to claim 3, wherein: A secret key sharing method for sharing a secret key between a sender device and an authorized receiver device arranged in a line-of-sight communication path,
By modulating a random number sequence, secret keys for optical space communication and RF band communication are respectively generated, and the generated secret keys are distributed from the sender device to the legitimate receiver device via optical space communication and RF band communication. Key distribution process,
A transmission step of receiving the secret key distributed via the optical space communication and the RF band communication by the key distribution step in the authorized receiver apparatus, selecting the same, and transmitting the selected key to the transmitter apparatus,
A communication secret key generation step of receiving information on the secret key selected by the authorized receiver device at the sender device and generating an optical space communication secret key and an RF band communication secret key based on the received content,
A final secret to be shared between the sender device and the authorized receiver device based on a common random number sequence included in the optical space communication secret key and the RF band communication secret key generated in the communication secret key generation step. A final secret key generation step of generating a key,
Secret key sharing method characterized by the following. A secret key sharing method for sharing a secret key between a sender device and an authorized receiver device arranged in a line-of-sight communication path,
In the sender device, the random number sequence is divided into a plurality, and a plurality of secret keys for optical space communication in which the divided random number sequences are respectively superimposed are generated. A key distribution step of distributing each of the plurality of secret keys by performing beam wandering so as to include the center of the beam while presetting the
A final secret key for generating a final secret key to be shared with the sender device based on a secret key included in each light beam distributed to the authorized receiver device through the optical space communication in the key distribution step. Having a generation step,
Secret key sharing method characterized by the following.

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