Efficient vernam's one time pad encryption scheme in optical space communication

Abstract

To provide an optical space communication system that efficiently enables data transmission even when a packet loss occurs in concealed packets.SOLUTION: In a system 1 for performing optical space communication between a transmitting device 3 and a receiving device 5, the transmitting device includes an encryption unit that encrypts data using an encryption key to obtain encrypted data, a packet generation unit that adds information regarding the data size of the encrypted data, data identification information, and information regarding the encryption key to the encrypted data to generate an optical space communication packet, and a packet transmitting unit that transmits the optical space communication packet to the receiving device, and the receiving device includes a packet receiving unit that receives the optical space communication packet, and a decryption unit that decrypts the encrypted data using information regarding the encryption key included in the optical space communication packet.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a system and method for performing free space optical communication, and more particularly to a system and method for performing concealed free space optical communication having packet loss resistance. [Background technology]

[0002] Japanese Patent No. 7120607 describes a secret key sharing system. This system makes it possible to carry out free space optical communication using packets that are made confidential using an encryption key. On the other hand, there has been a demand for a free space optical communication system that allows efficient data transmission even when packet loss occurs in confidential packets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7120607 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an optical space communications system that enables efficient data transmission even when a packet loss occurs in a concealed packet. [Means for solving the problem]

[0005] This invention is based on the knowledge that, as a countermeasure against packet loss, by adding the data size, data ID, and initial address of key ID to each packet, encryption key synchronization can be ensured, and since this information is repeatedly transmitted, packet loss can be efficiently detected. If there is a gap in the data ID number, a retransmission request is transmitted by RF, making it possible to provide resistance to packet loss.

[0006] The first invention relates to a system 1 for performing free space optical communication between a transmitting device and a receiving device. The system includes a transmitting device 3 and a receiving device 5. The transmitting device 3 has an encryption unit 11, a packet generation unit 13, and a packet transmission unit 15. The encryption unit 11 is an element for encrypting data using an encryption key to obtain encrypted data. The packet generation unit 13 is an element for adding information on the data size of the encrypted data, data identification information, and information on the encryption key to the encrypted data to generate a packet for optical space communication. The packet transmission unit 15 is an element for transmitting the packet for optical space communication to the receiving device 5. The receiving device 5 also includes a packet receiving unit 21 and a decryption unit 23. The packet receiving unit 21 is an element for receiving packets for optical space communication. The decryption unit 23 is an element for decrypting encrypted data using information on an encryption key included in the packets for optical space communication.

[0007] Examples of data identification information include the file number of the data and a number in the file identified by the file number of the data. An example of information related to the encryption key is a key start number. Thus, in this example, the same file number is assigned to multiple packets and sent multiple times. The key start number also means the starting address of the encryption key.

[0008] A preferred example of the above system 1 further includes a packet count acquisition unit 17 . The packet count acquisition unit 17 is an element that uses optical space climate information, which is information about the climate of the optical space where optical space communication is performed, and the required number of times to transmit an optical space communication packet in the optical space climate information as training data to construct a learning model that determines the number of times to transmit an optical space communication packet, and determines the number of times to transmit an optical space communication packet using the optical space climate information and the learning model.

[0009] In a preferred example of the above system 1, the receiving device 5 further includes a non-received data information acquiring unit 25 and an RF transmitting unit 27. The non-received data information acquiring unit 25 is an element for analyzing an optical space communication packet and acquiring identification information related to non-received data, which is data that has not been correctly received among the data. The RF transmitting unit 27 is an element for transmitting identification information related to non-received data due to packet loss to the transmitting device 3 by using RF band communication. In this example, the transmitting device 3 further includes an RF receiving unit 19 that receives identification information related to the non-received data. Then, the packet transmitting unit 15 transmits to the receiving device 5 a retransmission packet, which is an optical space communication packet including encrypted data identified by the identification information related to the non-received data. In this example, if there is a gap in the data number of the received data, a packet loss is likely to have occurred, so a transmission request can be made via RF.

[0010] The second invention relates to a method for performing free space optical communication between a transmitting device and a receiving device. This invention is basically a method for performing free space optical communication using the above-mentioned system. The transmitting device 3 performs an encryption step, a packet generating step, and a packet transmitting step. That is, the sending device 3 encrypts the data using the encryption key to obtain encrypted data (encryption step). The transmitting device 3 adds information on the data size of the encrypted data, data identification information, and information on the encryption key to the encrypted data, and generates a packet for optical space communications (packet generating step). The transmitting device 3 transmits the optical space communications packet to the receiving device 5 (packet transmitting step). Then, the receiving device 5 performs a packet receiving step and a decoding step. That is, the receiving device 5 receives the optical space communication packet (packet receiving step). The receiving device 5 decrypts the encrypted data using information about the encryption key included in the optical space communications packet (decryption step). Effect of the Invention

[0011] The present invention can provide an optical space communications system that enables efficient data transmission even when a packet loss occurs in a concealed packet. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram of a system for performing free space optical communications. [Diagram 2] FIG. 2 is a conceptual diagram showing an image of the data format. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art.

[0014] FIG. 1 is a block diagram of a system for performing free space optical communication. As shown in FIG. 1, the system 1 includes a transmitting device 3 and a receiving device 5. The system 1 is a system for performing free space optical communication between the transmitting device and the receiving device. The system 1 is mainly used for optical communication between a satellite and the ground. In optical communication between a satellite and the ground, packet loss occurs very frequently. Since the system is resistant to packet loss, it can be preferably used for optical communication between a satellite and the ground. In the system, an encryption key can be shared between the transmitting device 3 and the receiving device 5. The transmitting device 3 and the receiving device 5 are implemented by a computer or a server.

[0015] The computer has an input unit, an output unit, a control unit, a calculation unit, and a storage unit, and each element is connected by a bus or the like so as to be able to exchange information. For example, the storage unit may store a control program or various information. When predetermined information is input from the input unit, the control unit reads out the control program stored in the storage unit. Then, the control unit appropriately reads out the information stored in the storage unit and transmits it to the calculation unit. Also, the control unit appropriately transmits the input information to the calculation unit. The calculation unit performs calculation processing using the various information received and stores it in the storage unit. The control unit reads out the calculation result stored in the storage unit and outputs it from the output unit. In this way, various processes and each process are executed. The various units and means execute these various processes. The computer may have a processor, and the processor may realize various functions and various processes. The computer may be standalone. A part of the functions of the computer may be distributed between a server and a terminal. In that case, it is preferable that the server and the terminal are able to exchange information through a network such as the Internet or an intranet. The computer may include a processor and a memory coupled to the processor. The memory may store instructions that, when executed by the processor, cause the computer to execute various processes or function as various elements. The computer may be provided with various teaching data to construct a learning model and realize various calculations by machine learning. In this case, the computer may perform various analyses using a learning model created by machine learning and deep learning of AI (artificial intelligence).

[0016] The transmitting device 3 includes an encryption unit 11, a packet generation unit 13, and a packet transmission unit 15. The transmitting device 3 may further include either or both of a packet count acquisition unit 17 and an RF reception unit 19. An example of the transmitting device 3 is a data communication device mounted on a satellite (e.g., a low-earth orbit satellite).

[0017] The encryption unit 11 is an element for encrypting data using an encryption key to obtain encrypted data. That is, the encryption unit 11 encrypts data using an encryption key to obtain encrypted data (encryption process). Methods for encrypting data are publicly known, and publicly known encryption methods and encryption systems can be appropriately adopted. In optical communication between a satellite and the ground, it is preferable to realize optical communication with high confidentiality (preferably completely confidential communication). From this perspective, an encryption method using a Vernam encryption key (for example, Vernam's one-time pad (OTP) encryption) is preferable. For example, Japanese Patent No. 3876324 describes a system in which a Vernam encryption key is shared between a transmitting device and a receiving device. In this example, the transmitting device has an encryption device, and selects a number sequence from a random number sequence output from a random number sequence sharing device according to a sampling rule, and uses this as a Vernam encryption key. Then, the received information (data) is Vernam encrypted using the generated Vernam encryption key. The receiving device has a decryption device. Then, the receiving device selects a number sequence from a random number sequence output from a random number sequence sharing device according to a sampling rule, and uses this as a Vernam encryption key. The receiving device then uses the generated Vernam cipher key to Vernam-decrypt the received information. One-Time Pad (OTP) encryption is an encryption method that uses a random number sequence at most once.

[0018] FIG. 2 is a conceptual diagram showing a configuration image of a data format. The transmitting device 3 receives data. This data may be data transmitted from another communication means or data read from a storage unit of the transmitting device 3. An example of the encryption unit 11 is an OTP encryption unit. The OTP encryption unit selects a number sequence from a random number sequence using a sampling rule, and generates a one-time pad (OTP) encryption key. The encryption unit 11 may receive not only data, but also identification information of the data. The OTP encryption unit encrypts the data using the OTP encryption key, and obtains OTP encrypted data. The OTP encryption unit obtains information related to the encryption key, such as a key start number, and stores it in the storage unit as appropriate. The OTP encryption unit may also store either or both of information related to the data size of the encrypted data and identification information of the data in the storage unit.

[0019] The packet generating unit 13 is an element for generating a packet for optical space communication by adding information on the data size of the encrypted data, data identification information, and information on the encryption key to the encrypted data. That is, the packet generating unit 13 adds information on the data size of the encrypted data, data identification information, and information on the encryption key to the encrypted data, and generates a packet for optical space communication (packet generating process). An example of the data identification information includes a file number of the data and a number in a file specified by the file number of the data. Another example of the data identification information is a data number. An example of the information on the encryption key is a key start number. For example, the packet generating unit 13 not only obtains OTP encrypted data from the encryption unit 11, but also receives other data from the encryption unit 11 or reads other data from the storage unit. In this way, the packet generating unit 13 obtains encrypted data, information on the data size of the encrypted data, data identification information, and information on the encryption key, and adds information on the data size of the encrypted data, data identification information, and information on the encryption key to the encrypted data. In this way, the packet generating unit 13 generates a packet for optical space communication. The packet generator 13 may perform interleaving processing as necessary, or may further add an error correction code such as a Reed-Solomon code to generate a packet for optical space communication. Also, as shown in FIG. 2, the encrypted data that has been subjected to various processes may be stored in a payload for optical communication to generate a packet for optical space communication. An example of a protocol for optical communication is a connectionless communication protocol, and a specific example is UDP. UDP is an abbreviation for User Data Protocol, and is a communication protocol that emphasizes high-speed communication. In this way, the packet for optical space communication may be one that has been appropriately subjected to known processing, so long as it contains data based on the encrypted data. Data is encrypted and packets for optical space communication are generated based on the above-mentioned protocol, so that key synchronization can be ensured.

[0020] The packet transmitting unit 15 is an element for transmitting the optical space communication packet to the receiving device 5. That is, the packet transmitting unit 15 transmits the optical space communication packet to the receiving device 5 (packet transmitting process). An example of the packet transmitting unit 15 is a QKD unit. QKD stands for quantum key distribution. The QKD unit converts the optical space communication packet into signal light, combines this with synchronization light, and outputs the combined light to the transmitting device 5. An example of the packet transmitting unit 15 is a telescope capable of outputting a beacon, and the optical space communication packet may be transmitted to the receiving device 5 by a light beam method.

[0021] The packet count acquisition unit 17 is an element for determining the number of times a packet for optical space communication is transmitted, using optical space weather information and a learning model (trained model). The packet count acquisition unit 17 obtains the number of times a packet for optical space communication is transmitted (packet transmission number acquisition process). The packet count acquisition unit 17 outputs the number of times a packet for optical space communication is transmitted to the packet generation unit 13 or the packet transmission unit 15. The packet transmission unit 15 receives the number of times a packet for optical space communication is transmitted, and transmits a certain packet that number of times. By transmitting the same packet multiple times, it is possible to provide resistance to packet loss. Furthermore, by setting the number of transmissions to an appropriate number, it is possible to improve the efficiency of processing.

[0022] The packet count acquisition unit 17 preferably uses machine learning to construct a trained model and obtain an appropriate packet transmission count. The trained model may be a trained model that uses optical space climate information, which is information about the climate of the optical space where optical space communication is performed, and the necessary transmission count of packets for optical space communication in the optical space climate information as training data to determine the number of times to transmit packets for optical space communication. Examples of the information about the climate of the optical space may be one or more of weather, cloud cover, temperature, humidity, satellite altitude, and aerosol concentration. By including the correct answer data in the training data, the accuracy of the trained model can be improved. In addition, by repeatedly performing optical communication and feeding back the results of the optical communication, the accuracy of the trained model can be improved. In addition, information about attenuation of light intensity due to atmospheric conditions and information about empirical values ​​of fading of optical packets may be used as training data.

[0023] The receiving device 5 includes a packet receiving unit 21 and a decoding unit 23. The receiving device 5 may further include a non-received data information acquiring unit 25 and an RF transmitting unit 27. An example of the receiving device 5 is receiving equipment provided in a ground station.

[0024] The packet receiving unit 21 is an element for receiving a packet for optical space communication. That is, the packet receiving unit 21 receives a packet for optical space communication (packet receiving step). For example, the packet receiving unit 21 receives the packet for optical space communication and separates it into a synchronization light and a signal light using, for example, an optical demultiplexer.

[0025] The decryption unit 23 is an element for decrypting encrypted data using information on the encryption key included in the optical space communication packet. The decryption unit 23 decrypts the encrypted data using information on the encryption key included in the optical space communication packet (decryption step). For example, the decryption unit 23 has a QKD (Quantum Key Distribution) module, and a key management unit having the QKD module creates an encryption key for decrypting the optical space communication packet using information on the encryption key. Then, the decryption unit 23 decrypts the encrypted data using the created encryption key. The decrypted data may be stored in a storage unit as appropriate, or may be output to a user's terminal.

[0026] In a preferred example of the system 1, the receiving device 5 further includes a non-received data information acquisition unit 25 and an RF transmitting unit 27. The transmitting device 3 further includes an RF receiving unit 19 that receives identification information related to the non-received data.

[0027] The non-received data information acquisition unit 25 is an element for analyzing the optical space communication packet and acquiring identification information regarding non-received data, which is data that has not been correctly received among the data. The non-received data information acquisition unit 25 analyzes the optical space communication packet, acquires the identification information of the data, and stores it in the storage unit. Then, if there is missing data, the non-received data information acquisition unit 25 regards the data as non-received data. If the identification information of the data is the file number of the data and a number in the file specified by the file number of the data, the non-received data information acquisition unit 25 reads the number in the file for the file number from the storage unit and checks whether all the numbers have been received. Then, if there is a number that has not been received for a certain file number, the non-received data information acquisition unit 25 acquires the file number and the data number in the file number as identification information regarding the non-received data. The non-received data information acquisition unit 25 may store the acquired identification information regarding the non-received data in the storage unit. When the identification information of the data is a data number, the non-received data information acquisition unit 25 reads the data number from the storage unit and causes the calculation unit to perform a calculation to find the data number that has not been received among the data numbers. As a result, if there is a data number that has not been received, the data number is acquired as identification information related to the non-received data. The non-received data information acquisition unit 25 may store the acquired identification information related to the non-received data in the storage unit.

[0028] The RF transmitting unit 27 is an element for transmitting identification information related to the non-received data to the transmitting device 3 by using RF band communication. The RF transmitting unit 27 transmits the identification information related to the non-received data to the transmitting device 3 by a wireless signal by using RF band communication (non-received data information transmitting step). The RF band communication is wireless communication that normally uses a frequency band lower than 750 MHz. An example of the RF transmitting unit 27 is an output device including an antenna.

[0029] The transmitting device 3 has an RF receiving unit 19 that receives the identification information related to the non-received data. The RF receiving unit 19 receives the identification information related to the non-received data (non-received data information receiving step). An example of the RF receiving unit 19 is an antenna. The RF receiving unit 19 converts the received radio signal into, for example, an electrical signal related to the identification information related to the non-received data. The identification information related to the non-received data is output to the packet generating unit 13 or the packet transmitting unit 15. The packet transmitting unit 15 transmits a retransmission packet to the receiving device 5. The retransmission packet is an optical space communication packet including encrypted data specified by the identification information related to the non-received data. This retransmission packet may be generated again by the packet generating unit 13 and output from the packet transmitting unit 15. It is extremely difficult to establish two-way communication between a satellite and the ground. In this example, if there is a jump in the data number of the received data, packet loss is considered, so a transmission request can be made by RF, and the device has resistance to packet loss. [Industrial Applicability]

[0030] The present invention can be used, for example, in the field of free space optical communications, etc. In particular, since the present invention has resistance to packet loss, it can be preferably used in the fields of satellite quantum key distribution and completely secure communications. [Explanation of symbols]

[0031] 1 System 3. Transmitting Device 5. Receiving device 11 Encryption section 13 Packet Generation Unit 15 Packet transmitter 17 Packet count acquisition unit 19 RF receiver 21 Packet receiver 23 Decoding section 25. Non-received data information acquisition unit 27 RF transmitter

Claims

1. A system for performing free space optical communication between a transmitting device and a receiving device, the transmitting device includes an encryption unit that encrypts data using an encryption key to obtain encrypted data; a packet generating unit that generates a packet for optical space communication by adding information on a data size of the encrypted data, identification information of the data, and information on the encryption key to the encrypted data; a packet transmitting unit that transmits the optical space communication packet to the receiving device, The receiving device includes a packet receiving unit for receiving the optical space communication packet; a decryption unit that decrypts the encrypted data using information about the encryption key included in the optical space communications packet.

2. 2. The system of claim 1, the identification information of the data includes a file number of the data and a number in a file identified by the file number of the data, The information regarding the encryption key is a key start number.

3. 2. The system of claim 1, constructing a learning model for determining the number of times to transmit the optical space communication packet by using optical space climate information, which is information about the climate of the optical space where the optical space communication is performed, and the required number of times to transmit the optical space communication packet in the optical space climate information as training data; The system further comprises a packet count acquisition unit that uses the optical space climate information and the learning model to determine the number of times the optical space communication packet is transmitted.

4. 2. The system of claim 1, The receiving device includes a non-received data information acquiring unit that analyzes the optical space communication packet and acquires identification information regarding non-received data, which is data that has not been correctly received among the data; an RF transmission unit that transmits identification information related to the non-received data to the transmission device using RF band communication; The transmitting device further includes an RF receiving unit for receiving identification information related to the non-received data; The packet transmitting unit transmits, to the receiving device, a retransmission packet which is an optical space communication packet including encrypted data identified by identification information relating to the non-received data.

5. A method for performing free space optical communication between a transmitting device and a receiving device, comprising: The transmitting device, an encryption step of encrypting data using an encryption key to obtain encrypted data; a packet generating step of adding information about a data size of the encrypted data, identification information of the data, and information about the encryption key to the encrypted data, and generating a packet for free space optical communications; a packet transmitting step of transmitting the optical space communication packet to the receiving device; a packet receiving step in which the receiving device receives the optical space communication packet; and a decryption step of decrypting the encrypted data by using information on the encryption key included in the optical space communications packet.

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