Encryption system and encryption method

Abstract

This encryption system comprises a management device, an encryption device, and a decryption device. The encryption device and the decryption device are connected to each other via a first transmission line which is a physical transmission path. The management device transmits, to the encryption device and the decryption device, cryptographic information relating to a cryptographic scheme that is used in the encryption device and the decryption device. The encryption device transmits, to the decryption device via the first transmission line, communication data encrypted by performing an encryption process on the basis of the cryptographic information received from the management device. The decryption device performs a decryption process on the communication data received from the encryption device via the first transmission line, on the basis of the cryptographic information received from the management device.

Description

Encryption system and encryption method

[0001] This application claims priority from Japanese Patent Application No. 2022-85213, filed May 25, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Patent Document 1 (JP 2001-7797 A) discloses the following encrypted communication system: That is, the encrypted communication system includes a plurality of terminal devices connected to a network via an encryption device having a table in which at least terminal information and encryption key information are registered in association with each other, and each encryption device includes: confirmation means for confirming, upon receiving communication data from the terminal device, whether encryption key information corresponding to the terminal information and an application type is present in the table; key seek packet transmitting means for transmitting a key seek packet setting the terminal information, application type, and encryption key information of the communication data if the confirmation means confirms that the corresponding encryption key information is not registered; and setting means for setting the encryption key information corresponding to the application type in the tables of the encryption device that sent the key seek packet and of each encryption device located on a relay route that relays the key seek packet, based on a key seek response packet sent from a destination terminal device in response to the key seek packet sent by the key seek packet transmitting means.

[0003] Furthermore, Patent Document 2 (JP 2020-145672 A) discloses a method for exchanging a combined encryption key between a first node and a second node as follows: In this method, the first node and the second node are connected through a first communication network and a second communication network, the first communication network is a quantum communication network, information is encoded on weak optical pulses, the first node and the second node exchange one or more first encryption keys on the first communication network and one or more second encryption keys on the second communication network, and the combined encryption key is formed by combining the one or more first encryption keys and the one or more second encryption keys such that the first node and the second node share knowledge of the combined encryption key.

[0004] JP 2001-7797 A JP 2020-145672 A

[0005] The encryption system of the present disclosure comprises a management device, an encryption device, and a decryption device, and the encryption device and the decryption device are connected to each other via a first transmission line which is a physical transmission path, and the management device transmits encryption information regarding the encryption method used in the encryption device and the decryption device to the encryption device and the decryption device, the encryption device generates encrypted data by encrypting communication data based on the encryption information received from the management device, and transmits the generated encrypted data to the decryption device via the first transmission line, and the decryption device decrypts the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.

[0006] The encryption method disclosed herein is an encryption method in an encryption system including a management device, an encryption device, and a decryption device, wherein the encryption device and the decryption device are connected to each other via a first transmission line which is a physical transmission path, and includes the steps of the management device transmitting encryption information regarding the encryption method used in the encryption device and the decryption device to the encryption device and the decryption device, the encryption device generating encrypted data by encrypting communication data based on the encryption information received from the management device, and transmitting the generated encrypted data to the decryption device via the first transmission line, and the decryption device performing decryption processing of the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.

[0007] One aspect of the present disclosure can be realized not only as an encryption system having such a characteristic processing unit, but also as a program for causing a computer to execute such characteristic processing steps, or as a semiconductor integrated circuit that realizes part or all of the encryption system.

[0008] FIG. 1 is a diagram illustrating a configuration of an encryption system according to a first embodiment of the present disclosure. FIG. 2 is an example of a correspondence table held by a management device and a communication device according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a sequence of encrypted communication in the encryption system according to the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating a configuration of an encryption system according to a second embodiment of the present disclosure. FIG. 5 is a diagram illustrating a configuration of an encryption system according to a third embodiment of the present disclosure. FIG. 6 is a diagram illustrating a configuration of an encryption system according to a fourth embodiment of the present disclosure.

[0009] Conventionally, techniques have been developed to improve security in networks.

[0010] [Problem to be Solved by the Present Disclosure] There is a demand for a technology that can further improve security in a network beyond the technology described in Patent Documents 1 and 2.

[0011] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide an encryption system and encryption method that can further improve security in a network.

[0012] [Effects of the Present Disclosure] According to the present disclosure, it is possible to further improve security in a network.

[0013] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0014] (1) An encryption system according to an embodiment of the present disclosure includes a management device, an encryption device, and a decryption device, and the encryption device and the decryption device are connected to each other via a first transmission line, which is a physical transmission path. The management device transmits encryption information regarding the encryption method used in the encryption device and the decryption device to the encryption device and the decryption device. The encryption device generates encrypted data by encrypting communication data based on the encryption information received from the management device, and transmits the generated encrypted data to the decryption device via the first transmission line. The decryption device decrypts the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.

[0015] In this way, the management device transmits encryption information regarding the encryption method to the encryption device and the decryption device, and the encryption device and the decryption device encrypt communication data and decrypt the encrypted data based on the encryption information received from the management device. Therefore, even if the encryption method is decrypted by an unauthorized device, the management device can change the encryption method and perform encryption and decryption according to the changed encryption method, thereby realizing robust encrypted communication in which communication data is difficult to intercept with a single successful attack, thereby further improving security in the network.

[0016] (2) In the above (1), the management device may transmit the encryption information to the encryption device and the decryption device via a second transmission line separate from the first transmission line.

[0017] With this configuration, the encryption method selected by the management device can be more safely notified to the encryption device and the decryption device.

[0018] (3) In (1) or (2) above, the management device, the encryption device, and the decryption device may retain correspondence information indicating the correspondence between the encryption information and the encryption method, and the management device may refer to the correspondence information and transmit the encryption information corresponding to the encryption method used in the encryption device and the decryption device to the encryption device and the decryption device, and the encryption device may refer to the correspondence information and encrypt the communication data in accordance with the encryption method corresponding to the encryption information received from the management device, and the decryption device may refer to the correspondence information and decrypt the encrypted data in accordance with the encryption method corresponding to the encryption information received from the management device.

[0019] With this configuration, the encryption method selected by the management device can be notified to the encryption device and the decryption device more safely with a simple configuration.

[0020] (4) In any one of (1) to (3) above, the management device may select the encryption method to be used in the encryption device and the decryption device depending on the confidentiality of the communication data.

[0021] With this configuration, an encryption method having encryption strength according to the confidentiality of the communication data can be used, so that highly confidential communication data can be transmitted more safely.

[0022] (5) In any of (1) to (4) above, the management device may select the encryption method to be used in the encryption device and the decryption device depending on the real-time characteristics required for the communication data.

[0023] With this configuration, an encryption method with a delay amount according to the real-time property required for communication data can be used, so that transmission delay can be reduced in applications that require real-time property.

[0024] (6) In any of (1) to (5) above, the encryption system may include a plurality of management devices, and the encryption device may encrypt the communication data in accordance with the encryption method identified based on the plurality of pieces of encryption information received from the plurality of management devices, respectively. The decryption device may decrypt the encrypted data in accordance with the encryption method identified based on the plurality of pieces of encryption information received from the plurality of management devices, respectively.

[0025] With this configuration, even if some of the multiple management devices are hacked or some of the multiple pieces of cryptographic information are intercepted, the cryptographic method used in the encryption device and decryption device cannot be deciphered, so the cryptographic method used in the encryption device and decryption device can be more safely notified to the encryption device and decryption device.

[0026] (7) In any of (1) to (6) above, a plurality of logical transmission paths may be formed using the first transmission line, and the management device may transmit the encryption information indicating a target transmission path among the plurality of logical transmission paths that is the subject of encrypted communication to the encryption device and the decryption device, and the encryption device may perform encryption processing of the communication data transmitted via the target transmission path indicated by the encryption information, and the decryption device may perform decryption processing of the encrypted data transmitted via the target transmission path indicated by the encryption information.

[0027] With this configuration, for example, multiple pieces of communication data can be transmitted using multiple transmission paths, and encrypted communication can be performed on a target transmission path among the multiple transmission paths, making it difficult for the communication data to be intercepted.

[0028] (8) The encryption method disclosed herein is an encryption method in an encryption system including a management device, an encryption device, and a decryption device, wherein the encryption device and the decryption device are connected to each other via a first transmission line, which is a physical transmission path, and includes the steps of: the management device transmitting encryption information regarding the encryption method used in the encryption device and the decryption device to the encryption device and the decryption device; the encryption device generating encrypted data by encrypting communication data based on the encryption information received from the management device, and transmitting the generated encrypted data to the decryption device via the first transmission line; and the decryption device performing decryption processing of the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.

[0029] In this way, the management device transmits encryption information regarding the encryption method to the encryption device and the decryption device, and the encryption device and the decryption device encrypt communication data and decrypt the encrypted data based on the encryption information received from the management device. Therefore, even if the encryption method is deciphered by an unauthorized device, the management device can change the encryption method and perform encryption and decryption according to the changed encryption method, thereby realizing robust encrypted communication in which communication data is difficult to intercept with a single successful attack, thereby further improving security in the network.

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and their description will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any manner.

[0031] First Embodiment [Configuration and Basic Operation] Fig. 1 is a diagram showing the configuration of an encryption system according to a first embodiment of the present disclosure. Referring to Fig. 1, an encryption system 301 includes a management device 201 and a plurality of communication devices 101. In Fig. 1, communication devices 101A and 101B are shown as representative examples of the communication devices 101. Communication device 101A is an example of an encryption device. Communication device 101B is an example of a decryption device.

[0032] For example, the encryption system 301 is used in a network in an industrial control system such as a factory or plant, etc. In this case, the communication device 101 is, for example, a PLC (Programmable Logic Controller) for controlling a robot, a sensor, or an actuator.

[0033] The plurality of communication devices 101 are connected to each other via a transmission line 1, which is a physical transmission path. The transmission line 1 is an example of a first transmission line. The transmission line 1 is, for example, a transmission line conforming to the CAN (Controller Area Network) (registered trademark) standard. Note that the transmission line 1 may be a transmission line conforming to the Ethernet (registered trademark) standard, or may be a transmission line for serial communication conforming to standards such as RS (Recommended Standard)-232C, RS-422A, and RS-485. The communication devices 101A and 101B may be configured to be connected via a WAN (Wide Area Network).

[0034] The encryption system 301 may be used in a home network or an in-vehicle network. When the encryption system 301 is used in an in-vehicle network, the communication device 101 and the management device 201 are an in-vehicle ECU (Electronic Control Unit).

[0035] The management device 201 is connected to a plurality of communication devices 101 via a transmission line 2, which is a physical transmission path. The transmission line 2 is an example of a second transmission line. The transmission line 2 is, for example, a transmission line that complies with the CAN standard. Note that the transmission line 2 may be a transmission line that complies with the Ethernet standard, or may be a transmission line for serial communication that complies with standards such as RS (Recommended Standard)-232C, RS-422A, and RS-485.

[0036] The communication device 101 performs encrypted communication via a transmission line 1. For example, the communication device 101A periodically or irregularly encrypts communication data to generate encrypted data, and transmits frames including the generated encrypted data to the communication device 101B via the transmission line 1. The communication device 101B receives frames from the communication device 101A via the transmission line 1 and decrypts the encrypted data included in the received frames.

[0037] Note that the communication devices 101A and 101B may be configured to perform bidirectional encrypted communication. More specifically, the communication device 101B periodically or irregularly transmits frames containing encrypted data to the communication device 101A via the transmission line 1. The communication device 101A receives frames from the communication device 101B via the transmission line 1 and decrypts the encrypted data contained in the received frames.

[0038] The management device 201 includes a method selection unit 81 and a storage unit 82. Part or all of the method selection unit 81 is realized, for example, by a processing circuit including one or more processors. The storage unit 82 is, for example, a non-volatile memory included in the processing circuit.

[0039] The communication device 101 includes a communication unit 11, a processing unit 21, and a security processing unit 51. The security processing unit 51 includes a receiving unit 61, a scheme identification unit 62, an encryption processing unit 63, and a storage unit 64. Some or all of the communication unit 11, the processing unit 21, the receiving unit 61, and the scheme identification unit 62 are realized, for example, by a processing circuit including one or more processors. The encryption processing unit 63 is realized, for example, by an FPGA (Field-Programmable Gate Array). The storage unit 64 is, for example, a non-volatile memory included in the processing circuit.

[0040] The security processing unit 51 may be built into the communication device 101 or may be built into an external adapter or connector connected to the communication device 101 .

[0041] The storage unit 64 in the communication device 101 stores an encryption key used in encrypted communication between the communication devices 101 .

[0042] 2 shows an example of a correspondence table held by the management device and the communication device according to the first embodiment of the present disclosure. Referring to FIG. 2, the storage unit 82 in the management device 201 and the storage unit 64 in the communication device 101 store a correspondence table Tb1 indicating the correspondence between method numbers and encryption methods used in encrypted communication between the communication devices 101. The correspondence table Tb1 is an example of correspondence information.

[0043] In the correspondence table Tb1, the encryption method corresponding to the method number "101" is "PRESENT", the encryption method corresponding to the method number "102" is "CLEFIA", the encryption method corresponding to the method number "103" is "SIMON", the encryption method corresponding to the method number "104" is "SPECK", the encryption method corresponding to the method number "201" is "ChaCha20", the encryption method corresponding to the method number "202" is "Enocoro-128 v2", the encryption method corresponding to the method number "203" is "Enocoro-80", the encryption method corresponding to the method number "204" is "Trivium", and the encryption method corresponding to the method number "301" is "AES (Advanced Encryption Standard)". The encryption method corresponding to the method number "302" is "Camellia", the encryption method corresponding to the method number "401" is "RSA", and the encryption method corresponding to the method number "402" is "Elliptic Curve Cryptography".

[0044] PRESENT, CLEFIA, SIMON, and SPECK are lightweight block ciphers with encryption strength of 80 bits or more. PRESENT, CLEFIA, SIMON, and SPECK are generally used for cryptographic communications, are fast, and have low implementation costs.

[0045] ChaCha20, Enocoro-128 v2, Enocoro-80, and Trivium are lightweight stream ciphers with encryption strength of 80 bits or more. ChaCha20, Enocoro-128 v2, Enocoro-80, and Trivium are generally used for cryptographic communications, and are fast, have low implementation costs, and are highly real-time capable.

[0046] AES and Camellia are common key cryptosystems listed in the e-Government recommended cipher list, and have encryption strength of 128 bits or more. AES and Camellia are generally used for cryptographic communications and have high encryption strength.

[0047] RSA and elliptic curve cryptography are public key cryptography methods listed on the e-Government recommended cryptography list, with encryption strength of 128 bits or more. RSA and elliptic curve cryptography are generally used for key exchange and electronic signatures, and offer high encryption strength without requiring the management of private keys of communicating parties.

[0048] (Transmission of Encryption Information) Referring back to FIG. 1, the management device 201 transmits encryption information relating to the encryption method used in the communication devices 101A and 101B to the communication devices 101A and 101B.

[0049] More specifically, the method selection unit 81 in the management device 201 selects an encryption method to be used in the encrypted communication between the communication devices 101A and 101B.

[0050] For example, the method selection unit 81 selects an encryption method depending on the type of application that generates the communication data transmitted in the communication devices 101A and 101B, the operating mode of the industrial control system in which the encryption system 301 is used, and the confidentiality of the communication data transmitted in the communication devices 101A and 101B.

[0051] The method selection unit 81 acquires a method number corresponding to the selected encryption method by referring to the correspondence table Tb1 in the storage unit 82. The method selection unit 81 generates encryption information including the acquired method number, and transmits a frame including the generated encryption information to the communication devices 101A and 101B via a physically independent transmission line 2 separate from the transmission line 1 for encrypted communication.

[0052] In the communication devices 101A and 101B, the receiver 61 receives a frame from the management device 201 via the transmission line 2 and acquires encryption information from the received frame. The receiver 61 outputs the acquired encryption information to the method identification unit 62.

[0053] The method identification unit 62 receives encryption information from the receiving unit 61 and identifies the encryption method corresponding to the method number indicated by the received encryption information by referring to the correspondence table Tb1 in the storage unit 64. The method identification unit 62 also acquires an encryption key to be used in the identified encryption method from the storage unit 64. The method identification unit 62 outputs encryption setting information indicating the identified encryption method and the acquired encryption key to the encryption processing unit 63.

[0054] The encryption processing unit 63 performs encryption processing for communication data addressed to other communication devices 101 and decryption processing for encrypted data received from other communication devices 101 using the encryption key indicated by the encryption setting information in accordance with the encryption method indicated by the encryption setting information received from the method identification unit 62.

[0055] The scheme selection unit 81 is not limited to the configuration of selecting the standardized encryption scheme described above, but can select any non-standardized encryption scheme.

[0056] (Encryption Processing) The communication device 101A generates encrypted data by performing encryption processing on the communication data based on the encryption information received from the management device 201, and transmits the generated encrypted data to the communication device 111B via the transmission line 1. For example, the communication device 101A refers to the correspondence table Tb1 and performs encryption processing on the communication data in accordance with the encryption method corresponding to the encryption information received from the management device 201.

[0057] More specifically, the processing unit 21 in the communication device 101A generates communication data addressed to the communication device 101B periodically or irregularly. The processing unit 21 outputs the generated communication data to the encryption processing unit 63.

[0058] The encryption processing unit 63 in the communication device 101A receives communication data from the processing unit 21 and encrypts the received communication data in accordance with the encryption method indicated in the encryption setting information received from the method identification unit 62. The encryption processing unit 63 outputs encrypted data, which is the encrypted communication data, to the processing unit 21.

[0059] The processing unit 21 in the communication device 101A receives the encrypted data from the encryption processing unit 63 and outputs the received encrypted data to the communication unit 11.

[0060] The communication unit 11 in the communication device 101A includes the encrypted data received from the processing unit 21 in a frame and transmits the frame to the communication device 101B via the transmission line 1.

[0061] (Decryption Process) The communication device 101B performs decryption process of the encrypted data received from the communication device 111A via the transmission line 1 based on the encryption information received from the management device 201. For example, the communication device 101B refers to the correspondence table Tb1 and performs decryption process of the encrypted data in accordance with the encryption method corresponding to the encryption information received from the management device 201.

[0062] The communication unit 11 in the communication device 101B receives a frame from the communication device 101A via the transmission line 1, and obtains encrypted data from the received frame. The communication unit 11 outputs the obtained encrypted data to the processing unit 21.

[0063] The processing unit 21 in the communication device 101B receives the encrypted data from the communication unit 11 and outputs the received encrypted data to the encryption processing unit 63.

[0064] The encryption processing unit 63 in the communication device 101B receives encrypted data from the processing unit 21 and acquires communication data by decrypting the received encrypted data using the encryption method indicated by the encryption setting information received from the method identification unit 62. The encryption processing unit 63 outputs the acquired communication data to the processing unit 21.

[0065] The processing unit 21 in the communication device 101B processes the communication data received from the encryption processing unit 63 .

[0066] (Switching of encryption methods) For example, the method selection unit 81 in the management device 201 dynamically switches the encryption method used in the communication devices 101A and 101B. More specifically, the method selection unit 81 periodically or irregularly transmits encryption information included in a frame to the communication devices 101A and 101B via the transmission line 2.

[0067] The method selection unit 81 also transmits timing information indicating the timing of switching the encryption method to the communication devices 101A and 101B via the transmission line 2. The timing information may be information including an absolute time indicating the timing of switching, information including a relative time based on the timing of the previous switching, or a timing signal such as a clock for synchronizing the timing of switching.

[0068] In the communication devices 101A and 101B, the receiving unit 61 outputs the timing information received from the management device 201 via the transmission line 2 to the method identifying unit 62.

[0069] The method identification unit 62 receives timing information from the receiving unit 61 and notifies the encryption processing unit 63 of the switching timing indicated by the received timing information.

[0070] The encryption processing unit 63 switches the encryption method at the switching timing notified by the method identification unit 62 .

[0071] (Switching Example 1) For example, the method selection unit 81 periodically switches the encryption method at a frequency according to the confidentiality of communication data transmitted between the communication devices 101A and 101B.

[0072] As an example, the scheme selection unit 81 switches the encryption scheme from PRESENT to CLEFIA and SIMON in that order at a switching timing according to a predetermined switching cycle Cc.

[0073] More specifically, in a state in which communication devices 101A and 101B are encrypting communication data and decrypting encrypted data in accordance with PRESENT, in order to switch the encryption method from PRESENT to CLEFIA, scheme selection unit 81 transmits encryption information including "102" as the scheme number to communication devices 101A and 101B via transmission line 2. Scheme selection unit 81 also transmits timing information indicating the timing of switching from PRESENT to CLEFIA to communication devices 101A and 101B via transmission line 2.

[0074] Thereafter, in a state in which communication devices 101A and 101B are encrypting communication data and decrypting encrypted data according to CLEFIA, in order to switch the encryption method from CLEFIA to SIMON, scheme selection unit 81 transmits encryption information including "103" as the scheme number to communication devices 101A and 101B via transmission line 2. Scheme selection unit 81 also transmits timing information indicating the timing of switching from CLEFIA to SIMON to communication devices 101A and 101B via transmission line 2.

[0075] The scheme selection unit 81 may be configured to switch encryption schemes at random timing instead of periodically switching encryption schemes. Alternatively, the scheme selection unit 81 may be configured to transmit encryption information including a random number as a scheme number to the communication devices 101A and 101B via the transmission line 2. Alternatively, the scheme selection unit 81 may be configured to create an encryption scheme switching plan and transmit encryption information including multiple scheme numbers based on the created switching plan to the communication devices 101A and 101B via the transmission line 2, or to transmit timing information indicating multiple switching timings based on the switching plan to the communication devices 101A and 101B via the transmission line 2.

[0076] (Switching Example 2) For example, the method selection unit 81 selects the encryption method to be used in the communication devices 101A and 101B depending on the confidentiality of communication data transmitted between the communication devices 101A and 101B.

[0077] More specifically, the scheme selection unit 81 stores in advance information indicating a confidential communication period during which highly confidential communication data is transmitted between the communication devices 101A and 101B. The scheme selection unit 81 selects, as the encryption scheme for the confidential communication period, a public key encryption scheme such as RSA and elliptic curve encryption or a common key encryption scheme such as AES and Camellia, which have higher encryption strength.

[0078] For example, if communication devices 101A and 101B are encrypting communication data and decrypting encrypted data according to PRESENT, which has an encryption strength of 80 bits, a predetermined time before the start time of the confidential communication period, scheme selection unit 81 transmits encryption information including "301" as the scheme number to communication devices 101A and 101B via transmission line 2 in order to switch the encryption scheme from PRESENT to AES, which has an encryption strength of 128 bits. In addition, scheme selection unit 81 further transmits timing information indicating the timing of switching from PRESENT to AES to communication devices 101A and 101B via transmission line 2.

[0079] (Switching Example 3) For example, the method selection unit 81 selects the encryption method to be used in the communication devices 101A and 101B in accordance with the real-time characteristics required for communication data transmitted in the communication devices 101A and 101B.

[0080] More specifically, the method selection unit 81 stores in advance information indicating a real-time communication period, which is a period during which communication data requiring high real-time performance is transmitted between the communication devices 101A and 101B. The method selection unit 81 selects, as the encryption method for the real-time communication period, a lightweight encryption stream cipher such as ChaCha20, Enocoro-128 v2, Enocoro-80, or Trivium, which has a higher real-time performance.

[0081] For example, when communication devices 101A and 101B are encrypting communication data and decrypting encrypted data in accordance with PRESENT a predetermined time before the start time of the real-time communication period, scheme selection unit 81 switches the encryption scheme from PRESENT to ChaCha20, which has high real-time characteristics, by transmitting encryption information including "201" as the scheme number to communication devices 101A and 101B via transmission line 2. Scheme selection unit 81 also transmits timing information indicating the timing of switching from PRESENT to ChaCha20 to communication devices 101A and 101B via transmission line 2.

[0082] The method selection unit 81 may switch the encryption method by combining some or all of the switching examples 1 to 3.

[0083] [Operation Flow] Fig. 3 is a diagram showing an example of a sequence of encrypted communication in the encryption system according to the first embodiment of the present disclosure. Fig. 3 shows the sequence of the above-mentioned switching example 1.

[0084] 3, first, communication device 101A generates encrypted data by encrypting communication data in accordance with PRESENT corresponding to method number "101," and transmits the generated encrypted data in a frame to communication device 101B via transmission line 1. Communication device 101B decrypts the encrypted data received from communication device 101A in accordance with PRESENT (step S11).

[0085] Next, the management device 201 transmits encryption information including the method number "102" and timing information indicating the timing of switching from PRESENT to CLEFIA to the communication devices 101A and 101B via the transmission line 2 in order to switch the encryption method at the switching timing according to the switching period Cc (step S12).

[0086] Next, the communication device 101A switches the encryption method to CLEFIA, which corresponds to the method number "102" indicated by the encryption information received from the management device 201, at the switching timing indicated by the timing information received from the management device 201 (step S13).

[0087] In addition, the communication device 101B switches the encryption method to CLEFIA, which corresponds to the method number "102" indicated by the encryption information received from the management device 201, at the switching timing indicated by the timing information received from the management device 201 (step S14).

[0088] Next, communication device 101A generates encrypted data by encrypting the communication data in accordance with CLEFIA, and transmits the generated encrypted data in a frame to communication device 101B via transmission line 1. Communication device 101B decrypts the encrypted data received from communication device 101A in accordance with CLEFIA (step S15).

[0089] Next, in order to switch the encryption method at the switching timing according to the switching period Cc, the management device 201 transmits encryption information including the method number "103" and timing information indicating the switching timing from CLEFIA to SIMON to the communication devices 101A and 101B via the transmission line 2 (step S16).

[0090] Next, the communication device 101A switches the encryption method to SIMON, which corresponds to the method number "103" indicated by the encryption information received from the management device 201, at the switching timing indicated by the timing information received from the management device 201 (step S17).

[0091] In addition, communication device 101B switches the encryption method to SIMON, which corresponds to method number "103" indicated by the encryption information received from management device 201, at the switching timing indicated by the timing information received from management device 201 (step S18).

[0092] Next, communication device 101A generates encrypted data by encrypting the communication data in accordance with SIMON, and transmits the generated encrypted data in a frame to communication device 101B via transmission line 1. Communication device 101B decrypts the encrypted data received from communication device 101A in accordance with SIMON (step S19).

[0093] The management device 201 may create a switching plan for switching the encryption method at the switching timing according to the switching cycle Cc, and in step S12, based on the created switching plan, transmit encryption information including the method numbers "102" and "103" and timing information indicating the switching timing from PRESENT to CLEFIA and from CLEFIA to SIMON to the communication devices 101A and 101B via the transmission line 2. In this case, the management device 201 does not perform the process of step S16.

[0094] Furthermore, in the encryption system 301 according to the embodiment of the present disclosure, the storage unit 82 in the management device 201 and the storage unit 64 in the communication device 101 are configured to store a correspondence table Tb1 indicating the correspondence between scheme numbers and encryption schemes used in encrypted communication between the communication devices 101. However, this is not limited to this. The storage units 82 and 64 may be configured not to store the correspondence table Tb1. In this case, the scheme selection unit 81 in the management device 201 transmits encryption information including the algorithm of the selected encryption scheme to the communication devices 101A and 101B, instead of transmitting encryption information including the scheme number to the communication devices 101A and 101B.

[0095] Furthermore, in the encryption system 301 according to the embodiment of the present disclosure, the management device 201 is configured to be connected to the communication device 101 via the transmission line 2, but this is not limiting. The management device 201 may be configured not to be connected to the communication device 101 via the transmission line 2. In this case, for example, the method selection unit 81 in the management device 201 transmits a frame including encryption information to the communication devices 101A and 101B via wireless communication.

[0096] Furthermore, in the encryption system 301 according to the embodiment of the present disclosure, the scheme selection unit 81 in the management device 201 is configured to transmit timing information to the communication devices 101A and 101B via the transmission line 2, but this is not limited thereto. The scheme selection unit 81 may be configured to transmit timing information to the communication device 101A via the transmission line 2 but not to transmit timing information to the communication device 101B. In this case, the encryption processing unit 63 in the communication device 101A switches the encryption scheme at the switching timing indicated by the timing information received by the receiving unit 61. Furthermore, before switching the encryption scheme, the encryption processing unit 63 includes information indicating that the encryption scheme will be switched in the communication data received from the processing unit 21, and outputs encrypted data generated by encrypting the communication data including the information to the processing unit 21. The processing unit 21 in the communication device 101A outputs the encrypted data received from the encryption processing unit 63 to the communication device 101B via the communication unit 11 and the transmission line 1.

[0097] However, there is a demand for technology that can further improve network security. In particular, when communication is performed over a transmission path that is not guaranteed to be secure, communication technology that can safely transmit confidential information is extremely important.

[0098] In conventional cryptographic communication technologies, the encryption method is often fixed. Therefore, if an unauthorized device decrypts the encryption, all communication data transmitted thereafter may be intercepted by the unauthorized device. Furthermore, in the technology described in Patent Document 1, only one transmission path is used to form a VPN (Virtual Private Network), resulting in low security. Furthermore, in the technology described in Patent Document 2, a shared key is distributed using photons, resulting in high implementation costs.

[0099] In contrast, in the encryption system 301 according to the first embodiment of the present disclosure, the management device 201 transmits encryption information relating to the encryption method used by the communication devices 101A and 101B to the communication devices 101A and 101B. The communication device 101A generates encrypted data by encrypting communication data based on the encryption information received from the management device 201. The communication device 101B decrypts the encrypted data based on the encryption information received from the management device 201.

[0100] In this manner, the management device 201 transmits encryption information regarding the encryption method to the communication devices 101A and 101B, and the communication devices 101A and 101B encrypt and decrypt communication data based on the encryption information received from the management device 201. This configuration allows the management device 201 to change the encryption method and perform encryption and decryption processes according to the changed encryption method, even if the encryption method is decrypted by an unauthorized device. This enables robust encrypted communication in which communication data is less likely to be intercepted by a single successful attack. Furthermore, in a conventional configuration in which encryption keys are switched between the communication devices 101A and 101B, if the encrypted communication between the communication devices 101A and 101B is decrypted by an attack, the new encryption key can also be easily decrypted. In contrast, with the above configuration, even if the encrypted communication between the communication devices 101A and 101B is decrypted by an attack, changing the encryption method on the management device 201 makes it difficult to decrypt the new encryption method. This further improves network security.

[0101] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0102] Second Embodiment This embodiment, as compared with the encryption system 301 according to the first embodiment, relates to an encryption system 302 in which communication data and encryption information are multiplexed on a transmission line 1. Other than the details described below, the encryption system 302 is the same as the encryption system 301 according to the first embodiment.

[0103] FIG. 4 is a diagram illustrating a configuration of an encryption system according to a second embodiment of the present disclosure. Referring to FIG. 4, compared to the encryption system 301, the encryption system 302 includes a communication device 102 instead of the communication device 101, and a management device 201 is connected to a plurality of communication devices 102 via a transmission line 1. In FIG. 4, communication devices 102A and 102B are representatively illustrated as the communication devices 102. The communication device 102A is an example of an encryption device. The communication device 102B is an example of a decryption device. In the encryption system 302, different logical transmission paths 1n and 1m are formed using the transmission line 1. That is, two logical paths are formed on the physical transmission line 1. The communication device 101 performs encrypted communication via the transmission path 1m.

[0104] The communication device 102 differs from the communication device 101 in that it includes a communication unit 12 instead of the communication unit 11 and a security processing unit 52 instead of the security processing unit 51. The security processing unit 52 does not include the receiving unit 61, unlike the security processing unit 51.

[0105] The scheme selection unit 81 transmits a frame including encryption information to the communication devices 102A and 102B via the transmission line 1.

[0106] For example, the scheme selection unit 81 transmits a frame including encryption information to the communication devices 102A and 102B via a logically independent transmission path 1n that is separate from the transmission path 1m for encrypted communication. More specifically, the scheme selection unit 81 transmits the encryption information to the communication devices 102A and 102B by frequency division multiplexing, time division multiplexing, or code division multiplexing the encryption information onto the transmission line 1 through which communication data is transmitted.

[0107] Furthermore, for example, the method selection unit 81 frequency-division multiplexes, time-division multiplexes, or code-division multiplexes the timing information onto the transmission line 1, thereby further transmitting the timing information to the communication devices 102A and 102B via the transmission line 1n.

[0108] In the communication devices 102A and 102B, the communication unit 12 receives a frame from the management device 201 via the transmission path 1n and acquires encryption information from the received frame. The communication unit 12 outputs the acquired encryption information to the method identification unit 62. The communication unit 12 also outputs timing information received from the management device 201 via the transmission path 1n to the method identification unit 62.

[0109] The method identification unit 62 receives encryption information from the communication unit 12, identifies an encryption method by referring to the correspondence table Tb1 in the storage unit 64, and obtains an encryption key to be used in the identified encryption method from the storage unit 64. The method identification unit 62 outputs encryption setting information indicating the identified encryption method and the obtained encryption key to the encryption processing unit 63. The method identification unit 62 also notifies the encryption processing unit 63 of the switching timing indicated by the timing information received from the communication unit 12.

[0110] The encryption processing unit 63 switches the encryption method in accordance with the encryption setting information received from the method specifying unit 62 at the switching timing notified by the method specifying unit 62 .

[0111] The processing unit 21 in the communication device 102A generates communication data addressed to the communication device 102B periodically or irregularly, and outputs the generated communication data to the encryption processing unit 63.

[0112] The encryption processing unit 63 in the communication device 102A generates encrypted data by encrypting the communication data received from the processing unit 21, and outputs the generated encrypted data to the processing unit 21.

[0113] The processing unit 21 in the communication device 102 A receives the encrypted data from the encryption processing unit 63 and outputs the received encrypted data to the communication unit 12 .

[0114] The communication unit 12 in the communication device 102A includes the encrypted data received from the processing unit 21 in a frame and transmits the frame to the communication device 102B via the transmission path 1m.

[0115] The communication unit 12 in the communication device 102B receives a frame from the communication device 102A via the transmission path 1m, obtains encrypted data from the received frame, and outputs the obtained encrypted data to the processing unit 21.

[0116] The processing unit 21 in the communication device 102 B receives the encrypted data from the communication unit 12 and outputs the received encrypted data to the encryption processing unit 63 .

[0117] The encryption processing unit 63 in the communication device 102B receives the encrypted data from the processing unit 21, decrypts the received encrypted data to obtain communication data, and outputs the obtained communication data to the processing unit 21.

[0118] The processing unit 21 in the communication device 102 B processes the communication data received from the encryption processing unit 63 .

[0119] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0120] <Third Embodiment> In contrast to the encryption system 301 according to the first embodiment, this embodiment relates to an encryption system 303 that includes a plurality of management devices 202. Other than the contents described below, the encryption system 303 is the same as the encryption system 301 according to the first embodiment.

[0121] FIG. 5 is a diagram illustrating a configuration of an encryption system according to a third embodiment of the present disclosure. Compared to encryption system 301, encryption system 303 includes a communication device 103 instead of communication device 101, and includes management devices 202A, 202B, and 202C, which are management devices 202, instead of management device 201. In FIG. 5, communication devices 103A and 103B are representatively illustrated as communication devices 103. Communication device 103A is an example of an encryption device. Communication device 103B is an example of a decryption device. The encryption system 303 may include two or four or more management devices 202. In encryption system 303, different logical transmission paths 2a, 2b, and 2c are formed using a transmission line 2. That is, three logical paths are formed on the physical transmission line 2.

[0122] The communication device 103 differs from the communication device 101 in that it includes a security processing unit 53 instead of the security processing unit 51. The security processing unit 53 differs from the security processing unit 51 in that it includes a scheme identification unit 65 instead of the scheme identification unit 62.

[0123] The management devices 202A, 202B, and 202C are connected to a plurality of communication devices 101 via a transmission line 2. Compared to the management device 201, the management device 202 includes a method selection unit 83 instead of the method selection unit 81.

[0124] The method selection unit 83 in each of the management devices 202A, 202B, and 202C selects an encryption method to be used in the encrypted communication between the communication devices 103A and 103B. Each method selection unit 83 refers to the correspondence table Tb1 in the storage unit 82 and obtains the method number corresponding to the selected encryption method.

[0125] For example, the method selection unit 83 in the management device 202A generates encryption information C1 including the first digit of the acquired method number, and transmits a frame including the generated encryption information C1 to the communication devices 103A and 103B via the transmission line 2.

[0126] Also, for example, the method selection unit 83 in the management device 202B generates encryption information C2 including the second digit value of the acquired method number, and transmits a frame including the generated encryption information C2 to the communication devices 103A and 103B via the transmission line 2.

[0127] Also, for example, the method selection unit 83 in the management device 202C generates encryption information C3 including the third digit value of the acquired method number, and transmits a frame including the generated encryption information C3 to the communication devices 103A and 103B via the transmission line 2.

[0128] As an example, the method selection unit 83 in the management device 202A transmits a frame including encryption information C2 to the communication devices 103A and 103B via the transmission path 2a. The method selection unit 83 in the management device 202B transmits a frame including encryption information C2 to the communication devices 103A and 103B via a logically independent transmission path 2b that is separate from the transmission path 2a for encryption information C1. The method selection unit 83 in the management device 202C transmits a frame including encryption information C3 to the communication devices 103A and 103B via a logically independent transmission path 2c that is separate from the transmission path 2b for encryption information C1 and the transmission path 2b for encryption information C2. That is, the management devices 202A, 202B, and 202C transmit the encryption information C1, C2, and C3 to the communication devices 102A and 102B by frequency division multiplexing, time division multiplexing, or code division multiplexing the encryption information C1, C2, and C3 on the transmission line 2.

[0129] The communication device 103A encrypts the communication data in accordance with an encryption method specified based on the multiple pieces of encryption information received from the multiple management devices 202. The communication device 103B decrypts the encrypted data in accordance with an encryption method specified based on the multiple pieces of encryption information received from the multiple management devices 202.

[0130] More specifically, in the communication devices 103A and 103B, the receiver 61 receives frames from the management devices 202A, 202B, and 202C via the transmission line 2, and acquires encryption information C1, C2, and C3 from the received frames. The receiver 61 outputs the acquired encryption information C1, C2, and C3 to the scheme identification unit 65.

[0131] The method identification unit 65 receives the encryption information C1, C2, and C3 from the receiving unit 61 and acquires a method number by combining the value indicated by the encryption information C1, the value indicated by the encryption information C2, and the value indicated by the encryption information C3. The method identification unit 65 then refers to the correspondence table Tb1 in the storage unit 64 to identify the encryption method corresponding to the acquired method number. The method identification unit 65 also acquires an encryption key to be used in the identified encryption method from the storage unit 64. The method identification unit 65 outputs encryption setting information indicating the identified encryption method and the acquired encryption key to the encryption processing unit 63.

[0132] The encryption processing unit 63 in the communication device 103A encrypts the communication data addressed to the communication device 103B using the encryption key indicated by the encryption setting information in accordance with the encryption method indicated by the encryption setting information received from the method specification unit 65. The encryption processing unit 63 in the communication device 103B decrypts the encrypted data received from the communication device 103A using the encryption key indicated by the encryption setting information in accordance with the encryption method indicated by the encryption setting information received from the method specification unit 65.

[0133] In the encryption system 303 according to the embodiment of the present disclosure, the management devices 202A, 202B, and 202C are configured to be connected to the multiple communication devices 101 via the transmission line 2, but this is not limited thereto. The management devices 202A, 202B, and 202C may be configured to be connected to the multiple communication devices 101 via physically separate transmission lines. In this case, the method selection unit 83 in the management device 202B transmits a frame including encryption information C2 to the communication devices 103A and 103B via a physically independent transmission line separate from the transmission line for encryption information C1. Furthermore, the method selection unit 83 in the management device 202C transmits a frame including encryption information C3 to the communication devices 103A and 103B via a physically independent transmission line separate from the transmission lines for encryption information C1 and encryption information C2.

[0134] As described above, in the encryption system 303 according to the embodiment of the present disclosure, the communication device 103A encrypts communication data in accordance with an encryption method identified based on the encryption information C1, C2, and C3 received from the management devices 202A, 202B, and 202C, respectively. The communication device 103B decrypts the encrypted data in accordance with the encryption method identified based on the encryption information C1, C2, and C3 received from the management devices 202A, 202B, and 202C, respectively.

[0135] In this case, to obtain the encryption method selected by the management devices 202A, 202B, and 202C, it is necessary to obtain all of the encryption information C1, C2, and C3 transmitted by the management devices 202A, 202B, and 202C. In order for an attacker to identify the encryption method used by the communication devices 103A and 103B, the attacker must either hack all of the management devices 202A, 202B, and 202C to obtain the encryption information C1, C2, and C3, or intercept the encryption information C1, C2, and C3 on the transmission line 2. Therefore, even if some of the management devices 202A, 202B, and 202C are hacked or some of the encryption information C1, C2, and C3 are intercepted, the encryption method used by the communication devices 103A and 103B cannot be decrypted, thereby further improving security.

[0136] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and their description will not be repeated.

[0137] Fourth Embodiment This embodiment relates to an encryption system 304 in which encrypted communication is performed via multiple transmission paths, as compared with the encryption system 301 according to the first embodiment. Except for the details described below, the encryption system 304 is the same as the encryption system 301 according to the first embodiment.

[0138] FIG. 6 is a diagram illustrating a configuration of an encryption system according to a fourth embodiment of the present disclosure. Compared to encryption system 301, encryption system 304 includes a communication device 104 instead of communication device 101, and a management device 203 instead of management device 201. In FIG. 6, communication devices 104A and 104B are representatively illustrated as communication devices 104. Communication device 104A is an example of an encryption device. Communication device 104B is an example of a decryption device. In encryption system 304, different logical transmission paths 1a, 1b, and 1c are formed using transmission line 1. That is, three logical paths are formed on physical transmission line 1.

[0139] Compared to the communication device 101, the communication device 104 includes a communication unit 13 instead of the communication unit 11, a processing unit 22 instead of the processing unit 21, and a security processing unit 54 instead of the security processing unit 51. Compared to the security processing unit 51, the security processing unit 54 includes a scheme identification unit 66 instead of the scheme identification unit 62, and a cryptography processing unit 67 instead of the cryptography processing unit 63.

[0140] Compared to the management device 201 , the management device 203 includes a method selection unit 84 instead of the method selection unit 81 .

[0141] The communication device 104 transmits a plurality of pieces of divided communication data via logically independent transmission paths 1a, 1b, and 1c.

[0142] For example, in the encryption system 304, the communication setting contents such as the connection order of communication data on the transmission paths 1a, 1b, and 1c are determined in advance by the management device 203.

[0143] The communication devices 104A and 104B acquire communication setting information indicating communication setting contents determined in advance by the management device 203. The communication device 104A transmits the divided communication data to the communication device 104B via the transmission paths 1a, 1b, and 1c in accordance with the concatenation order indicated in the communication setting information. The communication device 104B concatenates the communication data received via the transmission paths 1a, 1b, and 1c in accordance with the concatenation order indicated in the communication setting information.

[0144] The scheme selection unit 84 in the management device 203 selects a target transmission path from among the transmission paths 1a, 1b, and 1c that is the transmission path to be subjected to encrypted communication, and an encryption scheme. For example, the scheme selection unit 84 selects the transmission paths 1a and 1b as the target transmission paths. The scheme selection unit 84 references the correspondence table Tb1 in the storage unit 82 to obtain a scheme number corresponding to the selected encryption scheme, generates encryption information including the obtained scheme number and the selected target transmission path, and transmits a frame including the generated encryption information to the communication devices 104A and 104B via the transmission line 2.

[0145] In the communication devices 101A and 101B, the receiver 61 receives a frame from the management device 201 via the transmission line 2 and acquires encryption information from the received frame. The receiver 61 outputs the acquired encryption information to the method identification unit 66.

[0146] The method identification unit 66 receives encryption information from the receiving unit 61, refers to the correspondence table Tb1 in the storage unit 64, identifies the encryption method corresponding to the method number indicated by the received encryption information, and obtains the encryption key to be used in the identified encryption method from the storage unit 64. The method identification unit 66 outputs encryption setting information indicating the target transmission path indicated by the encryption information, the identified encryption method, and the obtained encryption key to the encryption processing unit 67.

[0147] The encryption processing unit 67 performs encryption processing for communication data addressed to other communication devices 104 and decryption processing for encrypted data received from other communication devices 104 using the encryption key indicated by the encryption setting information in accordance with the encryption method indicated by the encryption setting information received from the method identification unit 66.

[0148] For example, the communication device 104A performs encryption processing on the communication data Da and Db to be transmitted via the target transmission path indicated by the encryption information.

[0149] More specifically, the processing unit 22 in the communication device 104A generates communication data Da to be transmitted to the communication device 101B via the transmission path 1a, communication data Db to be transmitted to the communication device 101B via the transmission path 1b, and communication data Dc to be transmitted to the communication device 101B via the transmission path 1c, and outputs the generated communication data Da, Db, and Dc to the encryption processing unit 67.

[0150] The encryption processing unit 67 in the communication device 104A receives the communication data Da, Db, and Dc from the processing unit 22, encrypts the communication data Da and Db in accordance with the encryption method indicated by the encryption setting information, in accordance with the linking order indicated by the communication setting information and the target transmission path indicated by the encryption setting information, and outputs encrypted data Dax and Dbx, which are the encrypted communication data Da and Db, to the processing unit 22. On the other hand, the encryption processing unit 67 outputs the communication data Dc to the processing unit 22 without encrypting it, in accordance with the target transmission path indicated by the encryption setting information.

[0151] The processing unit 22 in the communication device 104A receives the encrypted data Dax, Dbx and the unencrypted communication data Dc from the encryption processing unit 67 and outputs the received encrypted data Dax, Dbx and the communication data Dc to the communication unit 13.

[0152] The communication unit 13 in the communication device 104A receives the encrypted data Dax, Dbx and communication data Dc from the processing unit 22, and transmits the frames to the communication device 104B via the transmission line 1. More specifically, the communication unit 13 transmits the encrypted data Dax, Dbx and communication data Dc to the communication device 104B via the transmission paths 1a, 1b, and 1c, respectively.

[0153] For example, the communication device 104B performs a decryption process on the encrypted data Dax and Dbx transmitted via the target transmission path indicated by the encryption information.

[0154] More specifically, the communication unit 13 in the communication device 104B receives a frame from the communication device 104A via the transmission line 1, and acquires the encrypted data Dax, Dbx and communication data Dc from the received frame. The communication unit 13 outputs the acquired encrypted data Dax, Dbx and communication data Dc to the processing unit 22.

[0155] The processing unit 22 in the communication device 104 B receives the encrypted data Dax, Dbx and communication data Dc from the communication unit 13 , and outputs the received encrypted data Dax, Dbx and communication data Dc to the encryption processing unit 67 .

[0156] The encryption processing unit 67 in the communication device 104B receives the encrypted data Dax, Dbx and communication data Dc from the processing unit 22, and obtains communication data Da, Db by decrypting the encrypted data Dax, Dbx using the encryption method indicated by the encryption setting information in accordance with the linking order indicated by the communication setting information and the target transmission path indicated by the encryption setting information, and outputs the obtained communication data Da, Db to the processing unit 22. On the other hand, the encryption processing unit 67 outputs the communication data Dc to the processing unit 22 without decrypting it in accordance with the target transmission path indicated by the encryption setting information.

[0157] The processing unit 22 in the communication device 104B concatenates the communication data Da, Db, and Dc received from the encryption processing unit 67 in accordance with the transmission order indicated by the encryption setting information, and processes the concatenated communication data Da, Db, and Dc.

[0158] The above-described embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0159] Each process (each function) in the above-described embodiments is realized by a processing circuit (circuitry) including one or more processors. The processing circuit may be configured as an integrated circuit or the like that combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the processes. The one or more processors may execute each of the processes according to the program read from the one or more memories, or may execute each of the processes according to a logic circuit designed in advance to execute each of the processes. The processor may be any of various processors suitable for computer control, such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit). Note that the physically separated processors may cooperate with each other to execute the processes. For example, the processors installed in the physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet to execute the processes. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a semiconductor memory, and then installed into the memory from the recording medium.

[0160] The above description includes the following additional features: [Supplementary Note 1] An encryption system comprising: a management device; an encryption device; and a decryption device, wherein the encryption device and the decryption device are connected to each other via a first transmission line that is a physical transmission path, wherein the management device transmits encryption information regarding an encryption method used in the encryption device and the decryption device to the encryption device and the decryption device, wherein the encryption device generates encrypted data by encrypting communication data based on the encryption information received from the management device and transmits the generated encrypted data to the decryption device via the first transmission line, wherein the decryption device decrypts the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device, and wherein the management device switches the encryption method used in the encryption device and the decryption device, and further transmits timing information indicating the timing of the encryption method switch to the encryption device and the decryption device.

[0161] REFERENCE SIGNS LIST 1 Transmission line (first transmission line) 2 Transmission line (second transmission line) 1a, 1b, 1c, 1m, 1n, 2a, 2b, 2c Transmission path 11, 12, 13 Communication unit 21, 22 Processing unit 51, 52, 53, 54 Security processing unit 61 Receiving unit 62, 65, 66 Scheme identification unit 63, 67 Encryption processing unit 64 Storage unit 81, 83, 84 Scheme selection unit 82 Storage unit 101, 102, 103, 104 Communication device 101A, 102A, 103A, 104A Communication device (encryption device) 101B, 102B, 103B, 104B Communication device (decryption device) 201, 202, 202A, 202B, 202C, 203 Management device 301, 302, 303, 304 Encryption system Tb1 Correspondence table (correspondence information)

Claims

1. A management device; An encryption device; a decoding device, the encryption device and the decryption device are connected to each other via a first transmission line which is a physical transmission path; the management device transmits encryption information relating to an encryption method used in the encryption device and the decryption device to the encryption device and the decryption device; the encryption device generates encrypted data by performing encryption processing on communication data based on the encryption information received from the management device, and transmits the generated encrypted data to the decryption device via the first transmission line; The decryption device performs a decryption process on the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.

2. 2. The encryption system according to claim 1, wherein the management device transmits the encryption information to the encryption device and the decryption device via a second transmission line separate from the first transmission line.

3. the management device, the encryption device, and the decryption device each hold correspondence information indicating a correspondence between the encryption information and the encryption method; the management device refers to the correspondence information and transmits to the encryption device and the decryption device the encryption information corresponding to the encryption method used in the encryption device and the decryption device; the encryption device refers to the correspondence information, and performs encryption processing of the communication data in accordance with the encryption method corresponding to the encryption information received from the management device; 3. The encryption system according to claim 1, wherein the decryption device refers to the correspondence information and performs decryption processing of the encrypted data in accordance with the encryption method corresponding to the encryption information received from the management device.

4. 3. The encryption system according to claim 1, wherein the management device selects the encryption method to be used in the encryption device and the decryption device depending on confidentiality of the communication data.

5. 3. The encryption system according to claim 1, wherein the management device selects the encryption method to be used in the encryption device and the decryption device in accordance with real-time characteristics required for the communication data.

6. The encryption system comprises: A plurality of the management devices are provided, the encryption device performs encryption processing of the communication data in accordance with the encryption method specified based on the plurality of pieces of encryption information received from the plurality of management devices, respectively; 3. The encryption system according to claim 1, wherein the decryption device performs decryption processing of the encrypted data in accordance with the encryption method specified based on the plurality of pieces of encryption information received from the plurality of management devices, respectively.

7. a plurality of logical transmission paths are formed using the first transmission line; the management device transmits the encryption information indicating a target transmission path that is a target of encrypted communication among the plurality of logical transmission paths to the encryption device and the decryption device; the encryption device generates the encrypted data by performing encryption processing on the first communication data to be transmitted via the target transmission path indicated by the encryption information, transmits the encrypted data to the decryption device via the target transmission path, and transmits the second communication data to the decryption device via the logical transmission path different from the target transmission path; The encryption system according to claim 1 or claim 2, wherein the decryption device obtains the first communication data by performing a decryption process on the encrypted data transmitted via the target transmission path indicated by the encryption information, and concatenates the first communication data with the second communication data transmitted via the logical transmission path different from the target transmission path.

8. An encryption system as described in claim 1 or claim 2, wherein the management device switches the encryption method at a frequency according to the confidentiality of the communication data by transmitting the encryption information to the encryption device and the decryption device.

9. An encryption method in an encryption system including a management device, an encryption device, and a decryption device, comprising: the encryption device and the decryption device are connected to each other via a first transmission line which is a physical transmission path; a step of the management device transmitting encryption information regarding an encryption method used in the encryption device and the decryption device to the encryption device and the decryption device; the encryption device performs encryption processing on communication data based on the encryption information received from the management device to generate encrypted data, and transmits the generated encrypted data to the decryption device via the first transmission line; and a step in which the decryption device performs a decryption process on the encrypted data received from the encryption device via the first transmission line based on the encryption information received from the management device.