Existence and tampering prevention technique using quantum key delivery and high-precision time synchronization technique

Abstract

The present invention provides a communication method that uses a cryptographic key and that is capable of performing time synchronization with high accuracy and preventing tampering.　In the communication method, a terminal (3) at an exchange, a plurality of relay stations (9a, 9b, 9c), and a terminal (11) of a transactor receive a cryptographic key (7d) from a space-time standard station (5), the plurality of relay stations (9a, 9b, 9c) transmit encrypted relay station information to the terminal (11) of the transactor, the terminal (11) of the transactor transmits, to a selected relay station (9a), transaction information to which the encrypted relay station information has been added, the selected relay station (9a) transmits, to the terminal (3) at the exchange, the transaction information to which reception time has been added, and, when time information at the standard time is within a predetermined delay time, the terminal (3) at the exchange receives the transaction information included in the transaction information to which the relay station information has been added.

Description

Presence and tamper prevention technology using quantum key distribution and high-precision time synchronization technology

[0001] The present invention relates to a communication method using an encryption key and a system used in the method.

[0002] Currently, new financial services using ICT are being implemented in financial transactions. In order to make it easier for new entrants to enter the market, standards are being set for the quality of financial system construction. These standards include financial regulations such as MiFID II and FINRA, and the Financial Industry Regulatory Authority. However, the time synchronization achieved by the NTP communication protocol, which distributes time information in the past and is based on millisecond accuracy, is no longer sufficient; microsecond accuracy is now required. Furthermore, while there is a requirement to store and make public historical information on transaction prices, quantities, and times as close to real time as possible, progress has been slow in building such systems in Japan. One factor behind this is the lack of a means of obtaining accurate time.

[0003] Traditionally, GNSS (Global Navigation Satellite System) has been widely used. GNSS is a collective term for satellite positioning systems such as GPS, GLONASS, Galileo, and Beidou. In recent years, research has begun into using quasi-zenith satellites (QZSS) for time acquisition. GNSS has been considered ideal for mission-critical networks that must remain operational 24 hours a day, 365 days a year, and has therefore been widely used in environments requiring time information. However, GNSS has been found to have significant vulnerabilities. GNSS satellites are installed approximately 20,000 km from Earth to cover every corner of the globe. As a result, GNSS signals become weak radio waves by the time they reach Earth, making them vulnerable to jamming. GNSS signals can also be easily accessed free of charge by private services, such as car navigation systems. Because it is not encrypted, it can easily be spoofed (a type of DoS attack, such as tampering with time information).

[0004] For this reason, encryption key sharing systems are considered to be effective for financial services. Encryption key sharing systems are described in Japanese Patent Application No. 2022-057435, Japanese Patent Laid-Open No. 2023-149074, and Japanese Patent Laid-Open No. 2023-93938. Meanwhile, encryption key sharing systems also require highly accurate time synchronization and prevention of tampering.

[0005] Japanese Patent Application No. 2022-057435 Japanese Patent Application Laid-Open No. 2023-149074 Japanese Patent Application Laid-Open No. 2023-93938

[0006] This specification provides a communication method and system using an encryption key that can perform time synchronization with high accuracy and prevent tampering.

[0007] The communication method using an encryption key includes an encryption key receiving step (S101), an encryption relay station information transmitting step (S102), a transaction information transmitting step (S103), a transaction information transmitting step with a receipt time added (S104), and a transaction information receiving step (S105). In this way, transaction information from the trader's terminal 11 is transmitted to the exchange terminal 3. Each step will be described below.

[0008] Encryption Key Receiving Step (S101) The exchange terminal 3 receives encryption keys 7a, 7b, 7c, and 7d from the space-time standard station 5. Furthermore, multiple relay stations 9a, 9b, and 9c, which are connected to the space-time standard station 5 via a communication network and share standard time with the space-time standard station 5, receive encryption keys 7a, 7b, and 7c from the space-time standard station 5. The trader's terminal 11 receives encryption key 7d from the space-time standard station 5. Any one or more of the exchange terminal 3, the space-time standard station 5, the multiple relay stations 9a, 9b, and 9c, and the trader's terminal 11 are connected to each other so as to be able to exchange information via a communication network. One or more of these may be present on a quantum key distribution (QKD) network. The encryption keys may be distributed via a quantum key distribution (QKD) network, by hand (by mail, etc.), or via a communication network.

[0009] Encrypted relay station information transmission step (S102) The multiple relay stations 9a, 9b, 9c encrypt the identification information of each relay station 9a, 9b, 9c and the time information based on standard time using the encryption keys 7a, 7b, 7c received by each relay station 9a, 9b, 9c to obtain encrypted relay station information. Then, in this step, the multiple relay stations 9a, 9b, 9c transmit the encrypted relay station information to the trader's terminal 11. The identification information of each relay station 9a, 9b, 9c may be set in advance.

[0010] Transaction information transmission step (S103) The trader's terminal 11 receives encrypted relay station information from multiple relay stations 9a, 9b, and 9c, adds the transaction information to the encrypted relay station information, and obtains the transaction information with the relay station information added. The trader's terminal 11 encrypts the transaction information with the received encryption key 7d with the relay station information added, and obtains the encrypted transaction information with the relay station information added. The trader's terminal 11 transmits the encrypted transaction information with the relay station information added to the selected relay station 9a, which is one of the multiple relay stations 9a, 9b, and 9c.

[0011] Transaction information transmission step after addition of receipt time (S104) The selected relay station 9a receives the transaction information after the addition of encrypted relay station information. The selected relay station 9a adds the time at which the selected relay station 9a received the transaction information after the addition of encrypted relay station information to the transaction information after the addition of encrypted relay station information, thereby obtaining transaction information after the addition of receipt time. The selected relay station 9a transmits the transaction information after the addition of receipt time to the exchange terminal 3. Note that the selected relay station 9a may encrypt the transaction information after the addition of receipt time using the encryption key 7a received from the space-time standard station 5, and then transmit the encrypted transaction information after the addition of receipt time to the exchange terminal 3.

[0012] Transaction Information Receiving Step (S105) The exchange terminal 3 receives the transaction information with the receipt time added. The exchange terminal 3 decrypts the transaction information with the receipt time added using the encryption keys 7a, 7b, 7c, and 7d, and obtains the standard time information encrypted by the relay stations 9a, 9b, and 9c. If the standard time information is within a predetermined delay time, the exchange terminal 3 receives the transaction information included in the transaction information with the relay station information added. The exchange terminal 3 can preferably analyze the location information of the relay station in the QKD network using the identification information of the relay stations 9a, 9b, and 9c. The exchange terminal 3 can also preferably analyze the location information of the trader's terminal 11 using the location information of the relay station in the QKD network. The identification information of the relay stations 9a, 9b, and 9c may include the ID information of the relay station and the location information of the relay station in the QKD network.

[0013] This specification can provide a communication method and system using an encryption key that can perform time synchronization with high precision and prevent tampering.

[0014] Fig. 1 is a conceptual diagram for explaining a communication system using an encryption key. Fig. 2 is a chart for explaining a communication method using an encryption key. Fig. 3 is a conceptual diagram showing an encryption key receiving process and an encryption relay station information transmitting process. Fig. 4 is a conceptual diagram for explaining a transaction information receiving process.

[0015] The following describes embodiments of the present invention with reference to the drawings. The present invention is not limited to the embodiments described below, but also includes appropriate modifications of the embodiments that are obvious to those skilled in the art.

[0016] FIG. 1 is a conceptual diagram illustrating a communication system using a cryptographic key. This system 1 includes an exchange terminal 3, a space-time standard station 5, multiple relay stations 9a, 9b, and 9c, and a trader terminal 11. These preferably include computers, including a memory unit and a processor storing a program. Any one or more of these are connected to a communication network so that information can be exchanged. One or more of these may reside on a quantum key decryption (QKD) network. The cryptographic key may be distributed via the quantum key decryption (QKD) network, by hand (by mail, etc.), or via a communication network. The quantum cryptography communication device includes, for example, a transmitter and a receiver. Quantum cryptography communication is performed between these devices using optical signals (laser light). The transmitter may be a mobile device, such as a communication satellite. The receiver may be a fixed station, such as a ground station (base station).

[0017] Exchange Terminal 3 The exchange terminal 3 is also referred to simply as the exchange 3. The exchange 3 may be a terminal of an organization or entity that conducts some kind of transaction, such as a financial institution, a securities company, a stock market, an e-commerce site, an ATM, a credit card payment site, or a cryptocurrency management site. The exchange 3 conducts various transactions based on transaction information from the trader 11. For this purpose, the exchange 3 has a user database that stores various information, such as identification information about the trader 11 and account information about the trader 11 associated with the identification information about the trader 11. The exchange 3 may be connected to a communication network or have a receiver (antenna) that receives wireless signals. The exchange 3 may also have an encryption key receiver for receiving the encryption keys 7a, 7b, 7c, and 7d from the space-time standard station 5. The exchange 3 may also have a storage unit for storing the encryption keys 7a, 7b, 7c, and 7d. The exchange 3 may receive time information based on standard time together with the encryption keys 7a, 7b, 7c, and 7d from the space-time standard station 5 and store the information in a storage unit.

[0018] Space-Time Standard Station 5 The space-time standard station 5 is an element that can provide the exchange 3 with a reference time (standard time). An example of the space-time standard station 5 is the National Institute of Information and Communications Technology and its terminal. Preferably, the space-time standard station 5 can provide the reference time (standard time) to one or both of the multiple relay stations 9a, 9b, and 9c and the trader's terminal 11. An example of the standard time is time using an atomic clock. The space-time standard station 5 can output the standard time, for example, as radio waves (wireless signals), optical signals, or information to a quantum cryptography (QKD) network. The space-time standard station 5 also creates and distributes encryption keys to various elements. In this example, the space-time standard station 5 distributes the standard time and encryption keys. However, two or more elements may distribute the standard time and encryption keys, respectively.

[0019] Multiple Relay Stations 9a, 9b, 9c The multiple relay stations 9a, 9b, 9c are elements connected to the space-time standard station 5 via a communication network and share standard time with the space-time standard station 5. Examples of the relay stations 9a, 9b, 9c are nodes in the network or terrestrial base stations. The relay stations 9a, 9b, 9c are also called lighthouses. The multiple relay stations 9a, 9b, 9c can obtain time information based on standard time from the space-time standard station 5. The standard time may be transmitted by radio waves or provided by wire. Alternatively, the space-time standard station 5 and the multiple relay stations 9a, 9b, 9c may exist on a quantum keying (QKD) network, and the multiple relay stations 9a, 9b, 9c may receive standard time using the quantum keying (QKD) network. Each relay station 9a, 9b, 9c stores predetermined identification information (ID) of the respective relay stations 9a, 9b, 9c. ９ａ , ID ９ｂ , ID ９ｃ Therefore, each of the relay stations 9a, 9b, and 9c stores identification information (ID ９ａ , ID ９ｂ , ID ９ｃ ) can be read out and used for various calculations.

[0020] Trader's terminal 11 The trader's terminal 11 is also referred to simply as the trader 11. Examples of the trader 11 include a mobile terminal owned by the trader and a computer operated by the trader. For example, if the trader 11 is a mobile terminal, the trader 11 is a mobile object.

[0021] Any one or more of the exchange 3, the space-time standard station 5, the multiple relay stations 9 a, 9 b, and 9 c, and the traders 11 are connected to each other via a communication network so as to be able to exchange information. One or more of these may be on a quantum cryptography (QKD) network.

[0022] A computer has an input unit, an output unit, a control unit, a calculation unit, and a memory unit, and each element is connected by a bus or the like to enable the exchange of information. For example, the memory unit may store a control program or various information. When predetermined information is input from the input unit, the control unit reads the control program stored in the memory unit. The control unit then reads the information stored in the memory unit as appropriate and transmits it to the calculation unit. The control unit also transmits the input information as appropriate to the calculation unit. The calculation unit performs calculation processing using the received various information and stores it in the memory unit. The control unit reads the calculation results stored in the memory unit and outputs them from the output unit. In this way, various processes and steps are performed. Each unit or means executes these various processes. A computer may have a processor, and the processor may realize various functions and steps. A computer may be standalone. A computer may have some of its functions distributed between a server and a terminal. In this case, it is preferable that the server and the terminal can exchange information via 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 perform various processes or function as various elements. The computer may be provided with various training data to construct a learning model and perform various calculations through machine learning. In this case, the computer may perform various analyses using the learning model created through machine learning and deep learning of AI (artificial intelligence).

[0023] FIG. 2 is a chart for explaining a communication method using an encryption key. As shown in FIG. 2, the communication method using an encryption key includes an encryption key receiving step (S101), an encryption relay station information transmitting step (S102), a transaction information transmitting step (S103), a transaction information transmitting step with a receipt time added (S104), and a transaction information receiving step (S105). In this manner, transaction information from the trader 11 is transmitted to the exchange 3. Various pieces of information are processed by a computer as digital information that can be processed by a computer. An example of digital information is binary information of 0 or 1. Each step will be described below.

[0024] FIG. 3 is a conceptual diagram showing the encryption key receiving process and the encryption relay station information transmitting process.

[0025] Encryption Key Receiving Step (S101) In one example, the space-time standard station 5 distributes all types of encryption keys 7a, 7b, 7c, and 7d to the exchange 3. Meanwhile, the space-time standard station 5 distributes some of the encryption keys 7a, 7b, 7c, and 7d distributed to the exchange 3 to multiple relay stations 9a, 9b, and 9c. Then, the space-time standard station 5 distributes encryption key 7d, which is some of the encryption keys 7a, 7b, 7c, and 7d distributed to the exchange 3 but has not been distributed to the multiple relay stations 9a, 9b, and 9c, to the transactor 11. The encryption key may be distributed via a quantum cryptography (QKD) network, by hand (by mail, etc.), or via a communication network. Methods for creating and distributing encryption keys are publicly known, as described in, for example, Japanese Patent Application No. 2022-057435, Japanese Patent Application Laid-Open No. 2023-149074, and Japanese Patent Application Laid-Open No. 2023-93938. The space-time standard station 5 may transmit the encryption keys 7a, 7b, 7c, and 7d together with time information when the encryption keys were transmitted (or generated). The encryption keys 7a, 7b, 7c, and 7d may include time information when the space-time standard station 5 generated the encryption keys. The exchange 3 then receives the encryption keys 7a, 7b, 7c, and 7d from the space-time standard station 5. The exchange 3 receives time information based on standard time from the space-time standard station 5. Therefore, the exchange 3 may store the time information when the encryption keys 7a, 7b, 7c, and 7d are received in a storage unit. Furthermore, the plurality of relay stations 9a, 9b, 9c receive encryption keys 7a, 7b, 7c from the space-time standard station 5. The plurality of relay stations 9a, 9b, 9c receive time information based on standard time from the space-time standard station 5. The relay stations 9a, 9b, 9c receive the time information based on standard time (T Ｓ１０１) may be stored in a memory unit. The trader 11 receives the encryption key 7d from the space-time standard station 5. The trader 11 receives time information based on standard time from the space-time standard station 5. The trader 11 may store the time based on standard time when the encryption key 7d was received in a memory unit. The received encryption keys 7a, 7b, 7c, and 7d are stored appropriately in the memory unit of the exchange 3, the memory unit of the relay stations 9a, 9b, and 9c, and the memory unit of the trader 11. The stored encryption keys 7a, 7b, 7c, and 7d are read from the memory unit based on program instructions and used for various calculations. The exchange 3, the relay stations 9a, 9b, and 9c, and the trader 11 may also store the time when the encryption keys 7a, 7b, 7c, and 7d were received.

[0026] Encrypted relay station information transmission step (S102) A plurality of relay stations 9a, 9b, and 9c transmit the identification information (ID) of each of the relay stations 9a, 9b, and 9c. ９ａ , ID ９ｂ , ID ９ｃ ) and the time information based on standard time are encrypted by the encryption keys 7a, 7b, and 7c. In this process, the multiple relay stations 9a, 9b, and 9c transmit the encrypted relay station information to the trader 11. This process will be described in detail below. In the following example, the time information based on standard time is the time (T Ｓ１０１ ) However, the time information based on standard time may be time based on standard time encrypted using encryption keys 7a, 7b, and 7c. Each of the relay stations 9a, 9b, and 9c receives time information based on standard time (S.T) from the space-time standard station 5. Each of the relay stations 9a, 9b, and 9c receives identification information (ID) of each of the relay stations 9a, 9b, and 9c. ９ａ , ID ９ｂ , ID ９ｃ ) stored in the storage unit. Furthermore, each of the relay stations 9a, 9b, and 9c stores in its storage unit the encryption keys 7a, 7b, and 7c received from the space-time standard station 5. The relay stations 9a, 9b, and 9c receive the identification information (ID ９ａ , ID ９ｂ , ID ９ｃ The relay stations 9a, 9b, and 9c then read out the time information (ST) and identification information (ID９ａ , ID ９ｂ , ID ９ｃ ) are encrypted using encryption keys 7a, 7b, 7c. In this way, the relay stations 9a, 9b, 9c obtain the encrypted relay station information. The encrypted relay station information may be stored in the memory units of the relay stations 9a, 9b, 9c as appropriate. Then, the multiple relay stations 9a, 9b, 9c transmit the encrypted relay station information to the trader 11. For example, the first relay station 9a receives time information (S.T) from the sky standard station 5. The memory unit of the first relay station 9a stores identification information (ID ９ａ The first relay station 9a stores the identification information (ID) and the encryption key 7a from the storage unit. ９ａ The first relay station 9a then reads out the time information (ST) and the identification information (ID ９ａ ) is encrypted. In this way, the first relay station 9a obtains the first encrypted relay station information. Then, the first relay station 9a transmits the first encrypted relay station information to the trader 11. Note that the identification information (ID) of the relay stations 9a, 9b, and 9c is also encrypted. ９ａ , ID ９ｂ , ID ９ｃ In this case, the location information of the relay stations 9a, 9b, and 9c may be encrypted together with the location information of the relay stations 9a, 9b, and 9c, which is regarded as encrypted relay station information.

[0027] Transaction Information Transmission Step (S103) The trader 11 receives encrypted relay station information from multiple relay stations 9a, 9b, and 9c. The trader 11 stores the received encrypted relay station information (e.g., first to third encrypted relay station information) in a memory unit. When transaction information (e.g., information such as transferring a certain amount to a certain account or purchasing a certain number of shares) is input to the trader 11, the memory unit of the trader 11 stores the transaction information. The trader 11 then reads the transaction information and the encrypted relay station information from the memory unit and performs a process of adding the transaction information to the encrypted relay station information. In this way, the trader 11 obtains the transaction information after the relay station information has been added. The obtained transaction information after the relay station information has been added is stored in the memory unit of the trader 11 as appropriate. The memory unit of the trader 11 stores a fourth encryption key 7d. The trader 11 reads out the encryption key 7d. The trader 11 then uses the encryption key 7d to encrypt the transaction information after the relay station information has been added. In this way, the trader 11 obtains the encrypted transaction information after the relay station information has been added. The trader 11 transmits the encrypted transaction information after the relay station information has been added to a selected relay station 9a, which is one of the multiple relay stations 9a, 9b, and 9c. In the following example, the first relay station 9a is the selected relay station 9a. Methods for selecting the selected relay station 9a are publicly known. For example, the relay station that transmitted the encrypted relay station information that the trader 11 received first may be set as the selected relay station. In this case, for example, the header portion of the encrypted relay station information includes information indicating the relay station address, and the trader 11 stores the information indicating the relay station address in a memory unit. Then, using this address information, the trader transmits the encrypted transaction information after the relay station information has been added to the selected relay station 9a. Alternatively, all of the multiple relay stations 9a, 9b, and 9c may be set as the selected relay stations. The trader 11 may receive time information based on standard time from the space-time standard station 5 and obtain transaction information with the encrypted relay station information added, including the time when the transaction information was entered (or the time when the transaction information was encrypted). In this case, the transaction information may include the time when the transaction was carried out.

[0028] Transaction information transmission step after addition of receipt time (S104) The selected relay station 9a receives the transaction information after the addition of encrypted relay station information. The memory unit of the selected relay station 9a stores this transaction information as appropriate. The selected relay station 9a receives time information based on standard time from the space-time standard station 5 as needed and stores it in its memory unit. The selected relay station 9a then adds to this transaction information the time information at which the selected relay station 9a received this transaction information. In this manner, the selected relay station 9a obtains the transaction information after the addition of receipt time. The selected relay station 9a stores the obtained transaction information after the addition of receipt time in its memory unit. The selected relay station 9a reads out the transaction information after the addition of receipt time from the memory unit. The selected relay station 9a then transmits the transaction information after the addition of receipt time to the exchange 3. Note that the selected relay station 9a may encrypt the transaction information after the addition of receipt time using the encryption key 7a and then transmit the encrypted transaction information after the addition of receipt time to the exchange 3.

[0029] Transaction Information Receiving Step (S105) Fig. 4 is a conceptual diagram for explaining the transaction information receiving step. The exchange 3 receives the transaction information with the addition of the reception time. The exchange 3 receives the time information (ST) based on standard time from the space-time standard station 5 and stores it in the memory unit. The exchange 3 receives the time information (ST) based on standard time from the space-time standard station 5 and stores it in the memory unit. Ｓ１０５ ) in the storage unit. The exchange 3 stores the transaction information with the receipt time added in its storage unit. The exchange 3 reads out the encryption keys 7a, 7b, 7c, and 7d from the storage unit. The exchange 3 decrypts the transaction information with the receipt time added using the encryption keys 7a, 7b, 7c, and 7d. In this way, the exchange 3 obtains the time information based on standard time encrypted by the relay stations 9a, 9b, and 9c.

[0030] Next, the exchange 3 makes a transaction decision as to whether or not to carry out the transaction. If the time information based on standard time is within a predetermined delay time, the exchange 3 receives the transaction information included in the transaction information after the relay station information has been added (or carries out the transaction). This can be done by calculating the delay time using the time information based on standard time encrypted by the relay stations 9a, 9b, and 9c and the time information based on standard time when the exchange 3 received the transaction information after the receipt time has been added. For example, the exchange 3 may obtain the time based on standard time (T Ｓ１０１ Then, the exchange 3 reads out the time (T Ｓ１０５ ) and time (T Ｓ１０１ ) and calculates the difference between the time (T Ｓ１０５ ) and time (T Ｓ１０１ ) is within a threshold, the transaction information included in the transaction information to which the relay station information has been added can be received. In the above example, the specific relay station 9a receives the encryption key 7a based on the standard time (T Ｓ１０１ ), and the time when the exchange 3 receives the transaction information with the added receipt time (T Ｓ１０５ However, the time difference may be a time difference other than the above. For example, the time difference may be a time (T Ｓ１０５ ) and the time when the selected relay station 9a obtained the encrypted relay station information (the time when encryption was performed), or Ｓ１０５ ) and the time when the selected relay station 9a transmitted the encrypted relay station information.

[0031] The exchange 3 may analyze the location information of the trader 11 (or location information in the QKD network) to determine whether the time information based on standard time is within a predetermined delay time. The exchange 3 may preferably analyze the location information of the relays 9 a, 9 b, and 9 c in the QKD network using the identification information of the relays 9 a, 9 b, and 9 c. For example, the exchange 3 may analyze the location information of the relays 9 a, 9 b, and 9 c using the identification information (ID ９ａ , ID ９ｂ , ID ９ｃ The exchange 3 stores the location information of the relay stations 9a, 9b, and 9c in the storage unit in association with the transaction information after the receipt time.９ａ , ID ９ｂ , ID ９ｃ ) to read the location information of the relay stations 9a, 9b, and 9c from the storage unit. The exchange 3 analyzes the location information of the trader 11, for example, using information regarding the time when the multiple relay stations 9a, 9b, and 9c transmitted the encrypted relay station information to the trader 11 and the time when the trader 11 received the encrypted relay station information from the multiple relay stations 9a, 9b, and 9c. That is, the exchange 3 calculates the distance between each relay station 9a, 9b, and 9c and the trader 11, and analyzes the location information of the trader 11 from the location information of the relay stations 9a, 9b, and 9c and the distance between each relay station 9a, 9b, and 9c and the trader 11. The exchange 3 may also use time information included in the encrypted relay station information instead of the time when the multiple relay stations 9a, 9b, and 9c transmitted the encrypted relay station information to the trader 11. In this way, the exchange 3 can preferably analyze the location information of the trader 11 using the location information of the relay stations. The exchange 3 may, for example, determine the time limit (delay time) for receiving the transaction information from the location information of the trader 11. Then, if the time information based on standard time is within a predetermined delay time, the exchange 3 may receive the transaction information included in the transaction information to which the relay station information has been added.

[0032] After the exchange 3 receives and approves the transaction information, the exchange 3 may carry out a transaction based on the transaction information.

[0033] The present invention can be used in the information and communication related industries.

[0034] 1 Communication system 3 Exchange terminal 5 Space-time standard station 7a, 7b, 7c, 7d Encryption key 9a, 9b, 9c Relay station 11 Trader's terminal

Claims

1. An encryption key receiving process in which an exchange terminal (3) receives an encryption key (7a, 7b, 7c, 7d) from a space-time standard station (5), and a plurality of relay stations (9a, 9b, 9c) connected to the space-time standard station (5) via a communication network and sharing standard time with the space-time standard station (5) receive the encryption key (7a, 7b, 7c) from the space-time standard station (5), and a trader's terminal (11) receives the encryption key (7d) from the space-time standard station (5); an encrypted relay station information transmission step in which the plurality of relay stations (9a, 9b, 9c) encrypt the identification information of each relay station (9a, 9b, 9c) and the time information based on the standard time using the encryption key (7a, 7b, 7c) received by each relay station (9a, 9b, 9c), obtain encrypted relay station information, and transmit the encrypted relay station information to the trader's terminal (11); a transaction information transmission step in which the trader's terminal (11) receives the encrypted relay station information from the multiple relay stations (9a, 9b, 9c), adds transaction information to the encrypted relay station information, obtains the transaction information after the relay station information has been added, encrypts the transaction information after the relay station information has been added with an encryption key (7d) received by the trader's terminal (11), obtains the encrypted transaction information after the relay station information has been added, and transmits the encrypted transaction information after the relay station information has been added to a selected relay station (9a) that is one of the multiple relay stations (9a, 9b, 9c); and a transaction information transmission step after the receipt time has been added in which the selected relay station (9a) receives the encrypted transaction information after the relay station information has been added, adds the time at which the selected relay station (9a) received the encrypted transaction information after the relay station information has been added to the encrypted transaction information after the relay station information has been added, obtains the transaction information after the receipt time has been added, and transmits the transaction information after the receipt time has been added to the exchange terminal (3). a transaction information receiving step in which the terminal (3) of the exchange receives the transaction information with the receipt time added, decrypts the transaction information with the receipt time added using the encryption key (7a, 7b, 7c, 7d), obtains the time information based on the standard time encrypted by the relay station (9a, 9b, 9c), and, if the time information based on the standard time is within a predetermined delay time, receives the transaction information included in the transaction information with the relay station information added.

2. The method of claim 1, wherein the communication network is a quantum key distribution (QKD) network.

3. A method according to claim 2, wherein the exchange terminal (3) can analyze the location information of the relay station (9a, 9b, 9c) in the QKD network using the identification information of the relay station, and can analyze the location information of the trader's terminal (11) using the location information of the relay station in the QKD network.

4. The method according to claim 2, wherein the identification information of the relay station (9a, 9b, 9c) includes ID information of the relay station and location information of the relay station in the QKD network.

5. A method according to claim 2, wherein the step of transmitting the transaction information after the addition of the receipt time is a step of the selected relay station (9a) encrypting the transaction information after the addition of the receipt time using an encryption key (7a) received from the space-time standard station (5), and then transmitting the encrypted transaction information after the addition of the receipt time to the terminal (3) of the exchange.

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