JP2013211633A - Communication device, encryption communication system, encryption communication program, and encryption communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device, encryption communication system, program, and encryption communication method for reducing delay in data communication to a communication device of a communication partner.SOLUTION: A communication device which is connected to a relay device and can communicate with a communication device of a communication partner through the relay device determines whether or not communication speed required for encryption communication is equal to or higher than a threshold through a VPN configured with the communication device of the communication partner; executes encryption communication of data according to a predetermined protocol through a VPN configured with the relay device when it is determined that the communication speed is lower than the threshold; and executes encryption communication of data according to other than the predetermined protocol through the VPN configured with the communication device of the communication partner.

Description

  The present invention provides a communication device, an encrypted communication system, a program, and a communication device that selectively use a VPN that relays a relay device and a VPN that does not relay according to the processing load of the relay device when performing encrypted communication with a communication device of a communication partner. And an encrypted communication method.

  Conventionally, a technique for performing encrypted communication between a plurality of nodes via the Internet or a dedicated / public line is known. For example, in the technique disclosed in Patent Document 1, a packet is encrypted at a transmitting node in accordance with a protocol such as IPsec (Internet Protocol security), and is decrypted at a receiving node. In the technique disclosed in Patent Document 1, a VPN (Virtual Private Network) is constructed in a format called a hub and spoke type, and encrypted communication is performed. When the VPN is constructed in the hub-and-spoke type, the node on the transmission side encrypts the packet. The transmitting node transmits the encrypted packet to the relay node. The relay node decrypts the encrypted packet, selects a receiving node to be transmitted, and encrypts the packet again. Next, the relay node transmits the encrypted packet again to the selected receiving node.

  In the technique disclosed in Patent Document 1, when the transmission side node detects that the amount of traffic between the transmission side node and the relay node exceeds a threshold, the transmission side node and the reception side node Build a VPN directly between them.

JP 2004-140482 A

  In the encrypted communication described in Patent Document 1 described above, a transmission-side node detects the amount of traffic between the transmission-side node and a relay node. The processing load of the relay node includes not only what is caused by the traffic amount with the transmitting side node but also what is caused by the traffic amount with other receiving side nodes. Therefore, it is desirable to detect the amount of traffic between a plurality of transmission side nodes to which the relay node is connected, and to transmit an instruction to directly construct a VPN between the transmission side node and the reception side node. In this configuration, the transmission-side node and the reception-side node that have received the VPN construction instruction construct a VPN between the transmission-side node and the reception-side node, and execute encrypted communication. There is a possibility that the communication speed of the encrypted communication between the transmission side node and the reception side node may be lowered depending on the communication environment between the transmission side node and the reception side node. When the communication speed decreases, there is a possibility that transmission / reception of encrypted data between the transmission side node and the reception side node is delayed, or encrypted packets cannot be transmitted / received.

  The present invention has been made to solve the above-described problems, and a communication device, an encrypted communication system, an encrypted communication program, and a communication device that reduce communication delay of encrypted data to a communication device of a communication partner, and An object is to provide an encrypted communication method.

  In order to achieve the above object, the present invention according to claim 1 is a communication device connected to a relay device that relays encrypted communication and capable of communicating with a communication device of a communication partner via the relay device, A first construction means for constructing a VPN with the relay apparatus; a VPN constructed by the first construction means; and a first encrypted communication means for performing encrypted communication with the communication apparatus of the communication partner via the relay apparatus. When the processing load of the relay device becomes larger than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the relay device; and the communication device of the communication partner And a receiving unit that receives the construction information for constructing the VPN from the relay device, and when the first request notification is received by the receiving unit, based on the construction information, the communication device and the VP of the communication partner A second constructing means for constructing the data, a judging means for judging whether or not a communication speed necessary for data to be encrypted and communicated via the VPN constructed by the second constructing means is equal to or higher than a threshold value, and the judgment Second encryption for performing encrypted communication of data other than a predetermined protocol with the communication apparatus of the communication partner via the VPN constructed by the second construction means when the necessary communication speed is determined to be less than the threshold by the means Communication means, and when the required communication speed is determined to be less than a threshold value by the determination means, the first encrypted communication means performs encrypted communication of the data of the predetermined protocol. It is.

  According to the communication device of the first aspect, when it is determined that the necessary communication speed is less than the threshold, the first encrypted communication means executes the encrypted communication of the data of the predetermined protocol, and the second encrypted communication. The means executes encrypted communication of data other than a predetermined protocol. Thereby, since data other than the predetermined protocol is encrypted and communicated by the second encrypted communication means, a decrease in the processing speed of the data is reduced. Further, since the first encrypted communication means performs encrypted communication of encrypted data of a predetermined protocol, the processing load on the relay device is reduced. Accordingly, it is possible to reduce the communication delay of the encrypted data to the communication device of the communication partner.

  In order to achieve the above object, the present invention according to claim 2 is the communication apparatus according to claim 1, wherein the determination means is encrypted and communicated via the VPN constructed by the second construction means. It is determined whether or not the necessary communication speed including the processing speed of the process of encrypting or decrypting the data is equal to or higher than the threshold value.

  According to the communication device of the second aspect, it is determined whether or not the communication speed including the processing speed of the process of encrypting or decrypting the data encrypted and transmitted via the VPN constructed by the second construction unit is equal to or higher than the threshold value. The As a result, it is determined whether or not the required communication speed is more than the threshold value. Therefore, it is possible to increase the possibility that the processing load of the relay device is reduced and the possibility that the communication delay of data to the communication device of the communication partner is reduced.

  In order to achieve the above object, the present invention according to claim 3 is the communication apparatus according to claim 2, wherein the determination unit is configured to communicate with the communication partner via the VPN constructed by the second construction unit. The time information received by the communication device of the communication partner is received from the communication device of the communication partner, and the data transmitted to the communication device is received from the communication device of the communication partner, and based on the time information, whether the required communication speed is equal to or higher than the threshold value. It is characterized by judging.

  According to the communication device of the third aspect, it is determined based on the time information whether the necessary communication speed exceeds the threshold value. As a result, it is determined whether or not the required communication speed is more than the threshold value. Therefore, it is possible to increase the possibility that the processing load of the relay device is reduced and the possibility that the communication delay of data to the communication device of the communication partner is reduced.

  In order to achieve the above object, the present invention according to claim 4 is the communication apparatus according to claim 3, wherein the reception unit is configured to transmit data of all protocols via the VPN constructed by the second construction unit. If the first request notification including a forced switching instruction that is an instruction to perform encrypted communication is received, and the determination unit determines that the necessary communication speed is less than a threshold value, the second configuration unit is configured. The second constructing unit reconstructs a VPN whose encryption strength is lower than the encryption strength of the VPN with the communication device of the communication partner, and the second encrypted communication unit stores all protocol data in the second The encrypted communication is performed via the VPN reconstructed by the construction means.

  According to the communication device of the fourth aspect, when the forcible switching instruction is included in the first request notification, a VPN whose encryption strength is lower than the encryption strength of the VPN constructed by the second construction means is constructed. Is done. As a result, the decrease in the processing speed of the data encrypted and communicated by the second encrypted communication means is reduced by the amount that the encryption strength is reduced. Therefore, even when the second encrypted communication means performs encrypted communication of all protocol data, the communication delay of the encrypted data to the communication device of the communication partner can be reduced.

  To achieve the above object, the present invention according to claim 5 is the communication apparatus according to any one of claims 1 to 4, wherein the determining means determines that the required communication speed is less than a threshold value. The first encrypted communication means encrypts and communicates data of a real-time protocol as the predetermined protocol, and the second encrypted communication means encrypts and communicates data other than the real-time protocol as data other than the predetermined protocol. It is characterized by doing.

  According to the communication device of the fifth aspect, when it is determined that the communication speed is less than the threshold, the first encrypted communication unit executes the encrypted communication of the data of the real-time protocol, and the second encrypted communication unit includes: Performs encrypted communication of data other than real-time protocols. As a result, the processing load of the relay apparatus is reduced by the amount that the encrypted communication of data other than the real-time protocol is executed by the second encrypted communication means. Since the data of the real-time protocol requiring real-time property is encrypted and communicated by the first encrypted communication means with the processing load of the relay device reduced, the communication delay of data requiring real-time property is reduced. Can be reduced.

  In order to achieve the above object, the present invention according to claim 6 is the communication apparatus according to any one of claims 1 to 5, wherein the amount of data encrypted by the second encrypted communication means is reduced. Detecting means for detecting, and after receiving the first request notice, the receiving means sends a second request notice which is a request for encrypted communication of encrypted data of all protocols by the first encrypted communication means. When received from the relay device, the detection means detects a pre-reception data amount before the second request notification is received and a post-reception data amount after the second request notification is received, The first encrypted communication means performs encrypted communication of encrypted data of all protocols when the amount of data after reception detected by the detection means is smaller than the amount of data before reception. Is.

  According to the communication device of claim 6, when the data amount after reception detected by the second detection means becomes smaller than the data amount before reception, the first encryption communication means encrypts data of all protocols. connect. As a result, the processing load on the relay device when the first encrypted communication means encrypts and communicates data for all protocols is smaller than the processing load on the relay device in a state where the first switching instruction is received. Therefore, even when the first encrypted communication means executes encrypted communication of data of all protocols, it is possible to reduce the communication delay of data to the communication partner communication apparatus.

  In order to achieve the above object, the present invention according to claim 7 is connected to a relay device that relays encrypted communication, and communicates with a communication device of a communication partner via the relay device. A first construction step of constructing a VPN with the relay device, a VPN constructed by the first construction step, and a first encrypted communication step of performing encrypted communication with the communication device of the communication partner via the relay device; When the processing load of the relay device becomes larger than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the relay device; and the communication device of the communication partner When receiving the first request notification by the receiving step, the receiving step for receiving the configuration information for constructing the VPN and the VPN, based on the construction information, A second construction step for constructing a VPN with the communication device of the communication partner, and whether or not the communication speed required for data to be encrypted and communicated via the VPN constructed by the second construction step is equal to or higher than a threshold value. A determination step for determining, and if the required communication speed is determined to be less than a threshold value by the determination step, data other than a predetermined protocol is transmitted to the communication apparatus of the communication partner via the VPN established by the second construction means A second encrypted communication step for performing encrypted communication, and when the determination step determines that the required communication speed is less than a threshold, the first encrypted communication step encrypts the data of the predetermined protocol. This is a program characterized by computerized communication.

  To achieve the above object, the present invention according to claim 8 is a method of a communication device connected to a relay device that relays encrypted communication and capable of communicating with a communication device of a communication partner via the relay device. A first construction step for constructing a VPN with the relay device, a VPN constructed by the first construction step, and a first encrypted communication for performing encrypted communication with the communication device of the communication partner via the relay device A first request notification that is a request for encrypted communication without relaying between the communication device of the communication partner and the relay device when the processing load of the relay device is greater than a threshold; A receiving step of receiving from the relay device building information for building a communication device and a VPN, and when receiving the first request notification by the receiving step, based on the building information, A second construction step for constructing a VPN with a communication apparatus of a communication partner, and determining whether or not a communication speed required for encrypted data communication via the VPN constructed by the second construction step is equal to or higher than a threshold value And when the required communication speed is determined to be less than the threshold by the determining step, data other than a predetermined protocol is encrypted with the communication apparatus of the communication partner via the VPN established by the second constructing means. A second encrypted communication step for performing encrypted communication, and when the required communication speed is determined to be less than a threshold value by the determining step, the first encrypted communication step encrypts the data of the predetermined protocol. It is the method characterized by doing.

To achieve the above object, the present invention according to claim 9 is an encrypted communication system comprising a communication device and a relay device that relays encrypted communication between the communication device and a communication device of a communication partner. The communication device performs encrypted communication with the communication device of the communication partner via the first construction means for constructing a VPN with the relay device, the VPN constructed by the first construction means, and the relay device. A first request notification that is a request for encrypted communication without relaying between the communication device of the communication partner and the relay device when the processing load of the relay device becomes greater than a threshold value; , When receiving the first request notification by the receiving means, the receiving means for receiving the communication apparatus and the construction information for constructing the VPN from the relay apparatus, based on the construction information, A second construction means for constructing a VPN with a communication device of the communication partner, and whether or not a communication speed required for encrypted data communication via the VPN constructed by the second construction means is equal to or higher than a threshold value. A determination means for determining, and if the required communication speed is determined to be less than a threshold by the determination means, data other than a predetermined protocol is exchanged with the communication apparatus of the communication partner via the VPN established by the second construction means A second encrypted communication means for performing encrypted communication; and the relay apparatus detects a processing load including a conversion processing load of a process of decrypting encrypted data and a process of encrypting data; and A relay device determining unit that determines whether or not the processing load detected by the relay device detecting unit is equal to or greater than a threshold; and A relay device transmitting unit configured to transmit the first request notification and the first construction information to a device, and when the determination unit determines that a necessary communication speed is less than a threshold, the first encrypted communication unit Performs encrypted communication of the data of the predetermined protocol, and after the first request notification is transmitted to the communication device by the relay device transmission unit, the relay device determination unit determines whether the processing load is equal to or greater than a threshold value. And when the relay device determination means determines again that the processing load is equal to or greater than a threshold value, the relay device transmission means is not encrypted communication between the communication device and the communication device of the communication partner. Request that at least one of the other communication devices of the first pair of other communication devices executing the encrypted communication of the first communication device perform encrypted communication without relaying the communication device with another communication device. Is A third request notification and second construction information for constructing a VPN with another communication device of the communication partner are transmitted.

  According to the encrypted communication system of claim 9, when it is determined that the processing load detected again by the relay device determination unit is equal to or greater than the threshold value, the relay device transmission unit includes the first pair of other communication devices. The third switching instruction and the second construction information are transmitted to at least one of the other communication devices. Thereby, in the encrypted communication processing between the communication device that has received the third switching instruction and the communication device of the communication partner, it is possible to reduce the communication delay of data to the communication device of the communication partner. Along with the reduction of the communication delay, the processing load can be further reduced in the relay apparatus that has received the switching completion notification.

  In order to achieve the above object, the present invention according to claim 10 is the encryption communication system according to claim 9, wherein the relay device detecting means performs a process of decrypting data and a process of encrypting data. Of the second pair that executes the encrypted communication that causes the processing load having the second largest ratio of the processing load caused by the encrypted communication of the communication device and the communication device of the communication partner. Specifying means for specifying the second communication device, wherein the relay device transmitting means uses the second pair of other communication devices specified by the specification means as the first pair of other communication devices, and sends the third request notification. And the second construction information are transmitted to at least one other communication device of the second pair of other communication devices.

  According to the encrypted communication system of the tenth aspect, when it is determined that the processing load detected again by the relay device determination unit is large, the relay device transmission unit has two ratios that are large in the processing load of the relay device. Encrypted communication is executed from the communication device without going through the relay device. Thereby, the processing load of the relay device can be further reduced.

It is a figure which shows schematic structure of the encryption communication system 1 which concerns on this embodiment. 2 is a hardware diagram of a router 2 in the encrypted communication system 1. FIG. It is a schematic diagram showing the content of SPD. It is a schematic diagram showing the content of SAD. FIG. 11 is a sequence diagram showing processing for transmitting an encrypted packet from IP telephone 21 to IP telephone 31 when the processing load on router 6 is heavy. It is a sequence diagram showing the process at the time of VPN being constructed | assembled in main mode. It is a sequence diagram showing the process at the time of VPN being constructed | assembled by aggressive mode It is a schematic diagram showing the content of an encryption packet. 4 is a flowchart showing main processing of a router 2. It is a figure showing the process which the router 2 and the router 3 encrypt and decode a dummy packet, and the time which transmits / receives a dummy packet. 4 is a flowchart showing main processing of a router 6.

  An encrypted communication system 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of the encrypted communication system 1.

  The encrypted communication system 1 includes routers 2 to 6, IP telephones 21, 31, 41, 51 and personal computers (PCs) 22, 32, 42, 52. The IP telephones 21, 31, 41, 51 and the PCs 22, 32, 42, 52 are connected to the routers 2-5 via the LAN. The routers 2 to 5 construct a VPN with the router 6. The VPN is a virtual private network configured in an IP network. That is, the routers 2 to 6 are VPN gateways. Routers 2 to 5 are examples of the communication device of the present invention. The router 6 is an example of the relay device of the present invention.

  The routers 2 to 5 encrypt the packets transmitted from the IP telephones 21, 31, 41, 51 and the PCs 22, 32, 42, 52, respectively. Next, the routers 2 to 5 transmit the encrypted packet to the router 6. When the router 6 receives the encrypted packet, the router 6 decrypts the encrypted packet. Next, the router 6 encrypts the decrypted packet and transmits it to the routers 2 to 5 different from the receiving router. The routers 2 to 5 decrypt the encrypted packet. The routers 2 to 5 transmit the decrypted packets to the IP telephones 21, 31, 41, 51 and the PCs 22, 32, 42, 52. That is, packets transmitted from the IP telephones 21, 31, 41, 51 and the PCs 22, 32, 42, 52 are sent to the IP telephones 21, 31, 41, 51 and the PCs 22, 32, 42, 52 via the router 6. Sent. This form of encrypted communication is called a hub-and-spoke type, in which routers 2 to 5 correspond to spokes and router 6 corresponds to a hub.

  In this embodiment, for example, IPsec (Security Architecture for Internet Protocol) is adopted when encrypted communication is performed via a VPN constructed on the Internet. IPsec is a protocol for encrypting data in a network layer. IPsec is composed of a plurality of protocols such as AH (Authentication Header), ESP (Encapsulated Security Payload), and IKE (Internet Key Exchange). Since these protocols are known, they will be briefly described.

  AH is a security protocol having an authentication function. ESP is a security protocol that encrypts the payload portion. IKE is a protocol for exchanging keys.

[Hardware configuration of router]
The hardware configuration of the router 2 will be described with reference to FIG. Since the hardware configurations of the routers 3 to 6 are the same as the hardware configuration of the router 2, description thereof is omitted. The router 2 includes a CPU 11, a flash memory 12, a RAM 13, a WAN side communication interface 14, and a LAN side communication interface 15. The CPU 11, the flash memory 12, the RAM 13, the WAN-side communication interface 14, and the LAN-side communication interface 15 are connected via a bus. The flash memory 12 stores a control program such as a main process described later that is processed by the CPU 11. The flash memory 12 stores SA (Security Association) as SAD (Security Association Database) described later. The flash memory 12 stores SP (Security Policy) as an SPD (Security Policy Database). The RAM 12 stores temporary data when the CPU 11 executes the control program. The communication interface 14 on the WAN side includes a port to which a LAN cable is connected, and transmits / receives encrypted packets to / from the router 6 via the VPN constructed in the IP network. The communication interface 15 on the LAN side includes a port to which a LAN cable is connected, and transmits / receives an unencrypted packet to / from the PC 7 via the LAN cable. The communication interface on the LAN side of the router 6 is connected to a private network via a LAN cable. A SIP server (not shown) is connected to the private network, and the router 6 and the SIP server are connected via the private network. The CPU 11 is an example of a computer according to the present invention.

  The SPD will be described with reference to FIG. The SPD is a database that stores SP. SP is information indicating whether or not encrypted communication is performed between two routers capable of encrypted communication. The SP stores a source address, a destination address, an upper layer protocol, an operation, and the like in association with one record. The source address is the IP telephone of the packet source or the IP address of the PC. The destination address is an IP telephone of the destination of the packet or the IP address of the PC. The upper layer protocol is a protocol of a packet included in the payload portion. The operation is information on whether or not to perform encrypted communication. In FIG. 3, “Accept” is stored in the operation column when communication is performed without encrypted communication, and “IPsec” is stored in the operation column when encrypted communication is performed using IPsec.

  The SAD will be described with reference to FIG. SAD is a database that stores SA. The SA is a connection established between two routers that perform encrypted communication. The SA stores a source address, a destination address, a start point address, an end point address, a security protocol, an upper layer protocol, an SPI (Security Parameter Index), an encryption key, an encryption algorithm, and the like in association with one record. The start point address is the IP address of the router that transmits the encrypted packet. The end point address is the IP address of the router that receives the encrypted packet. AH or ESP is designated as the security protocol. SPI is information for identifying the SA. The encryption key is a key used for packet encryption when two routers perform encrypted communication. The encryption algorithm is an algorithm such as 3DES-CBC or DES-CBC.

  With reference to FIG. 5, a sequence when a packet is transmitted from IP telephone 21 to IP telephone 31 will be described.

[Operation when the processing load of the router 6 is small]
In S1, the router 2 and the router 6 construct a VPN. Next, in S2, the router 6 and the router 3 construct a VPN. The CPU 11 of the router 2 that executes the process of S1 is an example of the first construction means of the present invention. The process of S1 is an example of the first construction step of the present invention.

  The construction of the VPN in S1 and S2 will be described with reference to FIG. 6 and FIG. 6 and 7 show an example of the process of S1 in which a VPN is constructed between the router 2 and the router 6. FIG. In order to construct a VPN, an SA must be generated between two routers that perform encrypted communication. SA is dynamically generated by IKE (Internet Key Exchange). In this SA generation process, the router 2 and the router 6 execute known processes called phase 1 and phase 2. Phase 1 is processed in either the main mode or the aggressive mode. When the execution of the phase 1 and phase 2 processes is completed, a VPN is established between the router 2 and the router 6. FIG. 6 is a sequence diagram in which the phase 1 process is executed in the main mode. FIG. 7 is a sequence diagram in which the phase 1 process is executed in the aggressive mode.

[Main mode]
In S101 illustrated in FIG. 6, the router 2 transmits an ISAKMP SA generation request to the router 6. This ISAKMP SA generation request is a packet that proposes generation of an ISAKMP SA between the router 2 and the router 6. ISAKMP SA is a channel for controlling IKE when SA is automatically generated by IKE. When this proposal packet is transmitted to the router 6, the process proceeds to S102.

  The proposal packet includes parameters for establishing an ISAKMP SA. This parameter includes an encryption algorithm, a hash algorithm, an authentication method, a parameter used for Diffie-Hellman exchange, and the like.

  The encryption algorithm is an algorithm used when ISAKMP SA is encrypted. One encryption algorithm is designated in S102, which will be described later, from 3DES-CBC, DES-CBC, and the like. The hash algorithm is an algorithm used for authentication in the establishment process of ISAKMP SA. One hash algorithm is designated from SHA-1, MD5, and the like. The authentication method is a method for authenticating a communication destination router. One authentication method is designated from PSK (Pre-Shared Key) authentication and public key authentication. In the following description, it is assumed that PSK authentication is designated as a parameter. The parameters used for the Diffie-Hellman exchange are parameters used when a common key is generated by the Diffie-Hellman exchange.

  In S102, the router 6 authenticates the parameters included in the received ISAKMP SA generation request. When the parameter is authenticated, it is determined that the generation of the ISAKMP SA is accepted, and a packet notifying the acceptance of the generation of the ISAKMP SA is transmitted to the router 2. When this notification packet is transmitted to the router 2, the process proceeds to S103 and S104.

  In S103 and S104, the router 2 and the router 6 generate random numbers. When the generation of the random number is finished, the process proceeds to S105 and S106.

  In S105 and S106, the router 2 and the router 6 transmit the generated random numbers to the other routers 2 and 6. This transmission and reception of random numbers is called Diffie-Hellman exchange. When the transmission of the random number is completed, the process proceeds to S107 and S108.

  In S107, the router 2 generates a common key from the random number generated in S103 and the random number received in S106. In S108, the router 6 generates a common key from the random number generated in S104 and the random number received in S105. That is, the router 2 and the router 6 generate the same common key. When the generation of the common key ends, the process proceeds to S109.

  In S109, the router 2 generates a hash value from the PSK preset between the router 2 and the router 6. The PSK is stored in the flash memory 12 of the router 2 and the router 6 in association with the IP addresses of the router 2 and the router 6. The router 2 transmits the generated hash value to the router 6. This hash value is encrypted with the common key generated in S107 and transmitted to the router 6. When the transmission of the hash value is completed, the process proceeds to S110.

  In S110, the router 6 decrypts the hash value using the common key generated in S108. From the decrypted hash value and the IP address of the router 2 assigned to the source address, it is authenticated that the router in communication is the router 2 in the processing of S101 to S109. If it is determined that the communicating router is the router 2, the process proceeds to S111. That is, PSK is used for authentication of a communication partner for constructing a VPN.

  In S <b> 111, the router 6 generates a hash value from PSK that is preset between the router 2 and the router 6. This hash value is encrypted with the common key generated in S108 and transmitted to the router 6. When the transmission of the hash value ends, the process proceeds to S112.

  In S112, the router 2 decrypts the hash value from the common key generated in S107. Based on the decrypted hash value and the IP address of the router 6 assigned to the address of the transmission source, it is authenticated in step S101 to S109 that the router that is communicating is the router 6. If it is determined that the communicating router is the router 6, the process proceeds to S113.

  The processing of S101 to S112 is called phase 1. The ISAKMP SA is established by the processing of S101 to S112. In subsequent steps S113 to S116, packets transmitted and received between the router 2 and the router 6 are encrypted with the common key generated in the ISAKMP SA establishment process.

  In S113, the router 2 transmits an IPsec SA generation request to the router 6. This IPsec SA generation request is a packet that proposes generation of an IPsec SA between the router 2 and the router 6. The router 2 adds a random number, an encryption algorithm, and a security protocol to the proposal packet. In S113, the random number assigned to the proposed packet is used to generate an encryption key used for packet encryption when communication is performed between the router 2 and the PC connected to the router 6. It is a random number. The encryption algorithm is an algorithm such as 3DES-CBC, DES-CBC, or AES. AH or ESP is designated as the security protocol. When this proposal packet is transmitted to the router 6, the process proceeds to S114.

  In S114, when the router 6 accepts the generation of the IPsec SA between the router 2 and the router 6, the router 6 generates an encryption key from the random number assigned to the received proposal packet. When the key generation is completed, the process proceeds to S115.

  The encryption algorithm transmitted / received in S113 and S114 will be described. The router 2 transmits a plurality of encryption algorithms to the router 6 in S113. When the router 6 receives the proposal packet in S114, the encryption algorithm stored in the flash memory 12 of the router 6 is extracted from the encryption algorithms included in the proposal packet. An encryption algorithm having the highest encryption strength is selected from the extracted encryption algorithms. The encryption strength of the encryption algorithm increases in the order of AES, 3DES-CBC, and DES-CBC. When an algorithm with high encryption strength is selected, generation of IPsec SA is accepted.

  In S <b> 115, the router 6 transmits a packet notifying acceptance of generation of the IPsec SA to the router 2. The router 6 gives a random number to this notification packet. When this notification packet is transmitted to the router 2, the process proceeds to S116.

  In S116, the router 2 generates an encryption key from the random number given to the notification packet. When the generation of the encryption key is completed, an establishment notification packet for notifying that the IPsec SA has been established is transmitted to the router 6.

  The processing of S113 to S116 is called phase 2. The VPN is constructed by executing Phase 1 that is the processing of S101 to S112 and Phase 2 that is the processing of S113 to S116. That is, in order to construct a VPN between two routers, PSK must be set between the router 2 and the router 6. When the VPN is constructed, a security protocol, an encryption key, and an encryption algorithm are stored in association with the SA start point address and end point address stored in the flash memory 12 of the routers 2 and 6. At this time, an SPI for identifying the SA is given to the SA. Two SAs are created: the SA of the encrypted packet transmitted from the router 2 to the router 6 and the SA of the encrypted packet transmitted from the router 6 to the router 2.

[Aggressive mode]
The aggressive mode will be described with reference to FIG. In S201, the router 2 generates a random number. When the generation of random numbers is completed, the process proceeds to S202.

  In S202, the router 2 transmits an ISAKMP SA generation request. This ISAKMP SA generation request includes the random number generated in S201. When the ISAKMP SA generation request is transmitted, the process proceeds to S203.

  In S203, the router 6 generates a random number. When the random number is generated, the process proceeds to S204.

  In S204, the router 6 authenticates the parameters included in the ISAKMP SA generation request. If it is determined to authenticate this parameter, a packet notifying acceptance of generation of ISAKMP SA is transmitted to the router 2. This notification packet includes the random number generated in S203 and the hash value generated from the PSK preset between the router 2 and the router 6. When the notification packet is transmitted to the router 2, the process proceeds to S205.

  In S205, the router 2 determines that the communicating router is the router in the processing of S201 to S204 based on the hash value included in the received notification packet and the IP address of the router 6 assigned to the transmission source address. 6 is authenticated. If it is determined that the communicating router is the router 6, the process proceeds to S206.

  In S206, the router 2 generates a common key from a random number included in the received notification packet. When the generation of the common key ends, the process proceeds to S207.

  In S <b> 207, the router 2 transmits to the router 6 an authentication packet including a hash value generated from PSK set in advance between the router 2 and the router 6. When the transmission of the authentication packet ends, the process proceeds to S208. This hash value is encrypted with the common key generated in S206.

In S208, based on the hash value included in the authentication packet and the IP address of the router 2 assigned to the transmission source address, the router 6 determines that the router in communication is the router 2 in the processing of S201 to S204. Authenticate. If it is determined that the communicating router is the router 6, the phase 1 in the aggressive mode is terminated, and the process proceeds to the phase 2.

  Returning to FIG. 5, the description will be continued. In the following description, description will be given with reference to FIG. In S <b> 3, the router 2 receives an unencrypted packet from the IP telephone 21. In this packet, as shown in the content of the unencrypted packet shown in FIG. 8A, the IP address of the IP telephone 31 is designated as the destination IP address, and the IP address of the IP telephone 21 is the source. It is a packet specified by an IP address. A description will be given assuming that data according to a real-time protocol (Real-time Transport Protocol) is included in the payload portion of this packet. In the following description, the real-time protocol is described as RTP.

  When the router 2 receives the packet transmitted from the IP telephone 21, the router 2 refers to the SPD stored in the flash memory 12 of the router 2. It is determined whether there is an SP that matches the destination IP address of the packet transmitted from the IP telephone 21, the IP address of the transmission source, and the protocol of the data included in the payload portion. When it is determined that there is an SP, the router 2 determines to transmit a packet to the destination IP telephone 31 by the communication method indicated in the operation of the SP. If there is no SP, the router 2 determines not to send a packet to the destination IP telephone 31. In the following description, it is assumed that IPSec is stored in the SP operation and a packet is transmitted by encrypted communication. When the router 2 determines to transmit a packet by encrypted communication, the router 2 refers to the SAD. Next, the router 2 matches the destination IP address assigned to the packet, the IP address of the transmission source, and the data protocol of the payload part, and the start point address is from the SA that is the IP address of the router 2, the encryption key, and Extract the encryption algorithm. The router 2 encrypts the packet transmitted from the IP telephone 21 using this encryption key and encryption algorithm. The router 2 adds the IP address of the destination router, the IP address of the transmission source router, and the SPI specified by the SA to the encrypted packet. The IP address of the router 6 which is the end point address is given to the address of the destination router. The IP address of the router 2 that is the start point address is given to the address of the transmission source router. As shown in the content of the encrypted packet shown in FIG. 8B, the end point address, the start point address, and the SPI are given to the encrypted packet. In the following description, an encryption key and an encryption method used between the router 2 and the router 6 are a first encryption key and a first encryption algorithm, respectively. The address of the destination router is stored in advance in the flash memory 12 as the SA end point address. That is, if the IP address of the destination router is not stored in the flash memory 12, encrypted communication with that router is not performed.

  Next, the router 2 transmits the encrypted packet to the router 6. This encrypted packet is transmitted to the router 6 via the VPN constructed in S1. In the following description, the encrypted packet is referred to as an encrypted packet. The router 6 receives the encrypted packet transmitted from the router 2. When the router 6 receives the encrypted packet, the router 6 refers to the SPI attached to the encrypted packet, and extracts the first encryption key and the first encryption algorithm from the SAD stored in the flash memory 12 of the router 6. The router 6 decrypts the encrypted packet by using the first encryption key and the first encryption algorithm. The content of the decrypted packet is the same as the content of the unencrypted packet transmitted from the IP telephone 21 shown in FIG. The CPU 11 of the router 2 that executes the process of S3 is an example of the first encrypted communication means of the present invention. The process of S3 of the router 2 is an example of the first encrypted communication step of the present invention.

  Next, the router 6 stores the source address, destination address, protocol, and packet size included in the decoded packet in the flash memory 12 of the router 6. As will be described later, the IP address of the IP telephone 21 is the transmission source address, the IP address of the IP telephone 31 is the destination address, the protocol of the data included in the payload portion is RTP, and the size of the data included in the payload portion is the packet. Size. When the storage in the flash memory 12 is completed, the router 6 refers to the SPD stored in the flash memory 12 of the router 6. The router 6 determines whether there is an SP that matches the destination IP address of the packet transmitted from the IP telephone 21, the IP address of the transmission source, and the data protocol included in the payload portion. If it is determined that there is an SP, the router 6 determines to transmit a packet to the destination IP telephone 31 by the communication method indicated by the operation of the SP. If there is no SP, the router 6 determines not to transmit a packet to the destination IP telephone 31. If it is determined that the packet is transmitted by encrypted communication, the SAD is referred to. Next, the router 6 matches the destination IP address assigned to the packet, the IP address of the transmission source, and the protocol of the payload portion, and the start point address is from the SA that is the IP address of the router 6, the encryption key, and the encryption Extraction algorithm. With this encryption key and encryption algorithm, the router 6 encrypts the packet transmitted from the IP telephone 21. The router 6 matches the destination IP address given to the decrypted packet, the source IP address, and the protocol of the payload portion, and the start point address is stored in the end point address from the SA that is the IP address of the router 6. Extract the IP address of the router. The router 6 assigns the IP address of the destination router, the IP address of the transmission source router, and the SPI specified by the SA to the encrypted packet. The address of the destination router is the IP address of the router 3 that is the extracted end point address, and the address of the source router is the IP address of the router 6 that is the start point address. When the encryption is completed, the router 6 transmits the encrypted packet to the router 3. In the following description, an encryption key and an encryption algorithm used between the router 6 and the router 3 are referred to as a second encryption key and a second encryption algorithm, respectively.

  Next, the router 3 that has received the encrypted packet transmitted from the router 6 refers to the SPI assigned to the encrypted packet, and stores the second encryption key and the second encryption algorithm in the flash memory 12 of the router 3. Extract from stored SAD. The router 3 decrypts the encrypted packet by using the second encryption key and the second encryption algorithm. When the decoding is completed, the router 3 refers to the destination address included in the header of the decoded packet and transmits the packet to the IP telephone 31.

[Operation when the processing load of the router 6 is large]
The router 6 that relays the encrypted packet in the processing of S1 to S3 described above periodically detects the processing load. The router 6 detects the current processing load based on the packet size stored in the flash memory 12. In S4, the router 6 determines whether or not the processing load is larger than a threshold value. This threshold value is preset and stored in the flash memory 12 of the router 6. In the following description, processing when it is determined that the processing load is large will be described.

  In S <b> 5, the router 6 selects a router to be switched for encrypted communication without using the router 6. When the router 6 enters a high load state, the packet size of the encrypted packet is calculated for each of the two routers performing encrypted communication. The router 6 selects two routers corresponding to data having the largest packet size for each of the two routers as a switching target. Specifically, the start point address and the end point address are extracted as information to be switched. In the following description, the two routers performing encrypted communication with the largest packet size will be described as router 2 and router 3. When the switching target is selected, the process proceeds to S6.

  In S6, the router 6 generates PSK. This PSK is used to construct a VPN between the router 2 and the router 3. Specifically, it is used in S109 and S207. This PSK is different from the PSK of the VPN construction process in S1 and S2. When the generation of PSK ends, the process proceeds to S7.

  In S7, the router 6 generates two construction information packets. The construction information packet includes the created PSK and the IP addresses of the router 2 and the router 3 in the payload portion. When the generation of the construction information packet is completed, the process proceeds to S8. The construction information packet is an example of the first request notification of the present invention. The PSK included in the construction information packet and the IP addresses of the router 2 and the router 3 are examples of the construction information of the present invention.

  In S8, the router 6 refers to the SA stored in the flash memory 12 and encrypts the construction information packet. One construction information packet is encrypted with the first encryption key and the first encryption algorithm. The other construction information packet is encrypted with the second encryption key and the second encryption algorithm. When the encryption of the construction information packet is completed, the router 6 gives the IP address of the router 2 and the SPI to the construction information packet encrypted with the first encryption key and the first encryption algorithm. The router 6 transmits the construction information packet provided with the IP address of the router 2 and the SPI to the router 2 via the VPN constructed with the router 2. The router 6 gives the IP address and SPI of the router 3 to the second encryption key and the construction information packet encrypted by the second encryption method. The router 6 transmits the construction information packet provided with the IP address of the router 3 and the SPI to the router 3 via the VPN constructed with the router 3. When the transmission of the construction information packet is completed, the process proceeds to S9. In S8, the CPU 11 of the router 2 that receives the construction information is an example of the receiving means of the present invention. In S8, the process of the router 2 that receives the construction information is an example of the reception step of the present invention. In S8, the CPU 11 of the router 6 that transmits the construction information is an example of the relay device transmission means of the present invention. The construction information packet transmitted to the router 2 and the router 3 is a VPN construction notification.

  In S <b> 9, the router 2 and the router 3 that have received the encrypted construction information packet construct a VPN between the router 2 and the router 3. This VPN construction process will be described later. When the VPN construction process ends, the process proceeds to S10.

  In S10, the router 2 transmits a construction completion notification to the router 6 and the router 3 via the IP network. This construction completion notification is a notification indicating that a VPN has been constructed between the router 2 and the router 3. The construction completion notification will be described later in detail. When the construction completion notification is transmitted, the process proceeds to S11.

  In S11, when receiving the construction completion notification, the router 6 stores the switching target in the flash memory 12 and updates the SAD. That is, the router 6 stores information indicating the router that transmitted the construction information packet in the flash memory 12. Specifically, the router 6 assigns a switched flag to the SA to which the IP addresses of the router 2 and the router 3 are assigned to the start address or the end address. The switched flag indicates that the encrypted communication path has been switched. Specific SAD update processing will be described later. When the switched flag is assigned, the process proceeds to S12.

  In S 12, the router 2 receives an unencrypted packet from the IP telephone 21. The router 2 performs encrypted communication with the router 3 via the VPN constructed in S1 or the VPN constructed in S9 according to the protocol of the data included in the payload portion of the received unencrypted packet. To do. Details will be described later.

  In S <b> 13, the router 2 measures the amount of data that is encrypted and communicated via the VPN established with the router 3. The communication data amount measurement process will be described later. When the measurement of the communication data amount is completed, the process proceeds to S14.

  In S <b> 14, the router 6 detects the current processing load based on the packet size stored in the flash memory 12. This process is the same as S4. The router 6 determines whether or not the processing load is larger than a threshold value. In the following description, processing when it is determined that the processing load is smaller than the threshold will be described. When it is determined that the processing load is smaller than the threshold, the router 6 acquires a switching target. Specifically, the SA with the switched flag is extracted. The two routers of the extracted SA start point address and end point address are to be switched. In the following description, the router 2 and the router 3 are described as switching targets. When the acquisition of the switching target is completed, the process proceeds to S15.

  In S <b> 15, the router 6 transmits a switch notification to the router 2 and the router 3. The switching notification is a notification for executing encrypted data of all protocols via the router 6. When the transmission of the switching notification is completed, the process proceeds to S16. The switching notification is an example of a second request notification according to the present invention.

  In S16, the router 2 that has received the switching notification measures the communication data amount. This communication data amount measurement process is the same as the process of S13. That is, immediately after receiving the switching notification, the encrypted packet is not transmitted to the router 3 by the VPN established with the router 6. When the measurement of the communication data amount is completed, the process proceeds to S17.

  In S17, the router 2 executes a switching determination process. Specifically, the router 2 determines whether or not the communication data amount measured in S16 is smaller than the communication data amount measured in S13. Hereinafter, a case where it is determined that the number has decreased will be described. If it is determined that the number has decreased, the process proceeds to S18.

  In S <b> 18, the router 2 gives a switched flag to the SA whose start point address or end point address is the IP address of the router 3. Next, the router 2 deletes the switched flag from the SA to which the switched flag is assigned. When the switched flag is deleted and the SAD update is completed, the process proceeds to S19.

  In S <b> 19, the router 2 transmits a switch completion notification to the router 6 and the router 3. In S20, the router 6 that has received the switch completion notification deletes the switched flag from the SAs to which the start point address and the end point address are the IP addresses of the router 2 and the router 3 and the switched flag is assigned. When the switched flag is deleted and the SAD update is completed, the process proceeds to S21. Since the process of S21 is the same as S3, description is abbreviate | omitted.

  The main process of the router 2 will be described with reference to FIG. The main process of the router 2 is executed by the CPU 11 of the router 2. The main processing program is stored in the flash memory 12. The main processing program is stored in a server (not shown) and transmitted to the router 2 in response to a download request from the router 2.

  In S31, it is determined whether a VPN construction notification is received. This VPN construction notification is a construction information packet transmitted to the router 2 in S8 of FIG. If it is determined that the VPN construction notification has been received, the process proceeds to S32. If it is determined that the VPN construction notification has not been received, the process proceeds to S44.

  In S32, the router 3 and the VPN are constructed. Specifically, referring to the SPI assigned to the encrypted construction information packet received in S31, the first encryption key and the first encryption algorithm are extracted from the SA stored in the flash memory 12. . The encrypted construction information packet is decrypted with the first encryption key and the first encryption algorithm. When the decryption of the construction information packet is finished, the SA whose end address is the IP address of the router 6 is extracted. A new SA is created by rewriting the end point address of the extracted SA with the IP address of the router 3 included in the decrypted construction information packet. Next, the router 2 gives a switched flag to the extracted SA. On the other hand, the router 3 extracts the SA whose end address is the IP address of the router 6. A new SA is created by rewriting the end point address of the extracted SA with the IP address of the router 2 included in the decrypted construction information packet. Next, the router 3 gives a switched flag to the extracted SA. When the creation of a new SA and the assignment of the switched flag are completed, the router 2 constructs a VPN between the router 2 and the router 3 using the PSK included in the construction information packet. The PSK is included in the construction information packet and stored in the flash memory 12 in association with the IP addresses of the router 2 and the router 3. This VPN construction process is the same as the process of S1. When the construction of the VPN ends, the process proceeds to S33. In S32, the CPU 11 of the router 2 that constructs the VPN with the router 3 is an example of the second construction means of the present invention. In S32, the processing of the router 3 that constructs the VPN with the router 3 is an example of the second construction step of the present invention.

  In S33, the encryption key, the encryption algorithm, and the SPI created in the VPN construction process with the router 3 are assigned to the newly created SA in S32, and the SAD is updated. When the assignment of the encryption key, encryption algorithm, and SPI ends, the process proceeds to S34. In the following description, the encryption key and encryption algorithm assigned to SA in S33 are referred to as a third encryption key and a third encryption algorithm.

  In S <b> 34, the dummy packet is transmitted to the router 3 via the VPN established with the router 3. The process of S34 will be specifically described with reference to FIG. At the current time, which is the time T0 when the encryption is started, an operation of encrypting the dummy packet included in the payload portion with the third encryption key and the third encryption algorithm is started. The time T0 when the encryption is started is included in the payload portion. In the encrypted dummy packet, the IP address of the router 3, the IP address of the router 2, the third encryption key, the SPI associated with the third encryption algorithm, and the router 2 transmit the dummy packet to the router 3. The current time, which is time T1, and identification data indicating a dummy packet are given. The encrypted dummy packet that has been assigned is transmitted to the router 3. The router 3 that has received the encrypted dummy packet detects identification data indicating the dummy packet, and determines that the received packet is a dummy packet. When determining that the router 3 is a dummy packet, the router 3 stores the time T2 at which the dummy packet is received in the RAM 13. When the storage at time T2 ends, the router 3 extracts the third encryption key and the third encryption algorithm from the SAD based on the SPI assigned to the encrypted dummy packet. Based on the extracted third encryption key and the third encryption algorithm, the router 3 decrypts the encrypted dummy packet. When the decryption is completed, the dummy packet including the time T0, the time T1, and the time T2 in the payload portion is encrypted with the third encryption key and the third encryption algorithm. In the encrypted dummy packet, the IP address of the router 2, the IP address of the router 3, the SPI associated with the third encryption key and the third encryption algorithm, and the router 3 transmit the dummy packet to the router 2. A current time as time T3 and identification data indicating a dummy packet are given. The encrypted dummy packet that has been assigned is transmitted to the router 2. The router 2 that has received the encrypted dummy packet detects identification data indicating the dummy packet, and determines that the received packet is a dummy packet. When determining that the router 2 is a dummy packet, the router 2 stores the time T4 at which the dummy packet is received in the RAM 13. When the storage at time T4 ends, the router 2 extracts the third encryption key and the third encryption algorithm from the SAD based on the SPI assigned to the encrypted dummy packet. Based on the extracted third encryption key and the third encryption algorithm, the router 3 decrypts the encrypted dummy packet. When the decoding is completed, the router 2 stores the time T5 when the decoding is completed and the times T0 to T4 in the RAM 13. When the times T0 to T5 are stored, the process proceeds to S35. Of the time T2 received from the router 3 and the time T3, at least the time T2 is an example of the time information of the present invention.

  The description will be continued with reference to FIG. In S <b> 35, the router 2 detects the communication speed and the processing speed from the times T <b> 0 to T <b> 5 stored in the RAM 13. The communication speed is defined by a time obtained by subtracting time T1 from time T2. The processing speed is defined as the sum of a time obtained by subtracting time T4 from time T5, a time obtained by subtracting time T2 from time T3, and a time obtained by subtracting time T0 from time T1. When the detection of the communication speed and the processing speed is completed, the process proceeds to S36.

  In S36, it is determined whether or not the communication speed is equal to or higher than a threshold value. The threshold value is stored in advance in the flash memory 12 of the router 2. If it is determined that the communication speed is equal to or higher than the threshold, the process proceeds to S37. If the communication speed is less than the threshold, the process proceeds to S40. When the communication speed is less than the threshold value, the time until the data transmitted from the router 2 via the VPN is received by the router 3 is slow. As a result, there is a high probability that a communication delay of data that is encrypted and communicated with the router 3 via the VPN is generated. In S36, the CPU 11 of the router 2 that determines whether or not the communication speed is equal to or higher than the threshold value is an example of a determination unit of the present invention. The processing of the router 2 that determines whether or not the communication speed is equal to or higher than the threshold in S36 is an example of the determination step of the present invention.

  In S37, it is determined whether or not the processing speed is equal to or higher than a threshold value. The threshold value is stored in advance in the flash memory 12 of the router 2. If it is determined that the processing speed is equal to or higher than the threshold, it is determined that all protocol packets are encrypted and communicated with the router 3 via the VPN, and the process proceeds to S38. If the processing speed is less than the threshold, the process proceeds to S40. When the processing speed is less than the threshold, it can be said that the processing speed of the process of encrypting and decrypting the data of the router 2 and the router 3 is low. When the processing speed is less than the threshold, there is a high probability that a communication delay of data that is encrypted and communicated with the router 3 via the VPN is generated. If it is determined that the processing speed is equal to or higher than the threshold, the SAD is not updated. As a result, when the processing speed is equal to or higher than the threshold value and the router 2 transmits the packet transmitted from the IP telephone 21 to the IP telephone 31 in S12 of FIG. 5, the router 2 performs this via the VPN constructed in S32. The packet is encrypted and transmitted to the router 3.

  On the other hand, if it is determined in S36 that the communication speed is less than the threshold value, or if it is determined in S37 that the processing speed is less than the threshold value, it is determined in S40 whether the forced switching notification is included in the VPN construction notification. The forced switching notification will be described later. If it is determined that the forced switching notification is included, the process proceeds to S41. If it is determined that the forced switching notification is not included, the process proceeds to S43.

  In S41, a VPN is established again with the router 3. The encryption strength of the VPN constructed again is lower than the encryption strength of the VPN constructed with the router 3 in S32. Specifically, when constructing the VPN again with the router 3, in S113 of FIG. 6, the router 2 performs an encryption algorithm other than the encryption algorithm when constructing the VPN with the router 3 in S32. Is sent to the router 6. That is, an IPsec SA generation request including an encryption algorithm other than the third encryption algorithm is transmitted to the router 6. For example, when the VPN encryption algorithm constructed in S32 is AES, 3DES-CBC and DES-CBC can be considered as the VPN encryption algorithm constructed again. When the VPN is constructed again, the process proceeds to S42.

  In S42, the SAD is updated. All protocol packets are encrypted and communicated via the reconstructed VPN. In S33, the SA whose end address is rewritten to the IP address of router 2 or router 3 is extracted. The extracted SA encryption key, encryption algorithm, and SPI are rewritten to the encryption key, encryption algorithm, and SPI when the VPN is constructed again with the router 3 in S41, and the SAD is updated. As a result, in S12 of FIG. 5, when the router 2 transmits the packet transmitted from the IP telephone 21 to the IP telephone 31, the packet is encrypted and transmitted to the router 3 via the VPN reconstructed in S41. To do. When the update of SAD is completed, the process proceeds to S38.

  When it is determined in S40 that the forced switching notification is not included in the VPN construction notification, in S43, the encrypted communication of the real-time packet is performed via the VPN constructed in S1, and the VPN constructed in S32 is performed. It is determined that encrypted communication other than real-time packets is performed. That is, in S33, the end point address is rewritten to the IP address of router 2 or router 3, and the upper layer protocol is RTP, RTSP (Real Time Streaming Protocol), and RTCP (Real-time Transport Control Protocol) SA is extracted. . Delete the extracted SA. Next, among the SAs to which the switched flag is assigned, SAs whose upper layer protocols are RTP, RTSP, and RTCP are extracted. The switched flag given to the extracted SA is deleted, and the SAD is updated. As a result, when the router 2 determines in S12 of FIG. 5 that the packet transmitted from the IP telephone 21 is transmitted to the IP telephone 31, the protocol of the packet is any one of RTP, RTSP, and RTCP. The packet is transmitted to the router 6 via the VPN constructed in S1. If it is determined that the protocol of the packet transmitted from the IP telephone 21 is not RTP, RTSP, or RTCP, this packet is transmitted to the router 3 via the VPN constructed in S32. When the update of SAD is completed, the process proceeds to S38. When the protocol of data included in the payload portion is any one of RTP, RTSP, and RTCP, the packet is described as a real-time packet. The encrypted communication of the real time protocol is executed via the router 6 by the process of S43. Of the encrypted communications between the router 2 and the router 3, protocols other than the real-time protocol are communicated without going through the router 6, so the processing load on the router 6 is reduced. Since the communication speed of the encrypted communication between the router 2 and the router 3 is low, or the processing speed of encryption and decryption is low, the real-time protocol data is constructed between the router 2 and the router 3. When encrypted communication is performed via the VPN, the data is received by the router 2 or the router 3 with a delay. On the other hand, since the real-time protocol data is encrypted and communicated via the router 6, the delay of the real-time protocol data is reduced.

  In S37, when it is determined that the communication speed is equal to or higher than the threshold value, or in S42 and S43, when the update of SAD is completed, a construction completion notification is transmitted to router 6 and router 3 in S38. When it is determined in S37 that the communication speed is equal to or higher than the threshold, a notification for performing encrypted communication of all protocols is transmitted to the router 6 and the router 3 via the VPN constructed in S32. When the SAD is updated in S42, a notification for performing encrypted communication of all protocols is transmitted to the router 6 and the router 3 via the VPN reconstructed in S41. When the SAD is updated in S43, the router 6 performs a notification of performing encrypted communication of the real-time packet via the VPN constructed in S1, and performing encrypted communication other than the real-time packet via the VPN constructed in S32. And to the router 3. Upon receiving this construction completion notification, the router 6 and the router 3 update the SAD. When the CPU 11 of the router 2 finishes sending the construction completion notification, the process proceeds to S39.

  In S39, the amount of data that is encrypted and communicated with the router 3 via the VPN is detected. This process is the process of S13 shown in FIG. Specifically, data that is encrypted and communicated with the router 3 through a VPN established during a certain period is extracted. The packet size of the data included in the payload portion of each extracted data to be encrypted and communicated is totaled. The aggregated packet size is stored in the flash memory 12 as a communication data amount. When the storage of the communication data amount ends, the process proceeds to S31. In S39, the CPU 11 of the router 2 that detects the amount of data that is encrypted and communicated with the router 3 via the VPN is an example of the detection means of the present invention. In S39, the processing of the router 2 that detects the amount of data that is encrypted and communicated with the router 3 via the VPN is an example of the detection step of the present invention. The communication data amount stored in S39 is an example of the pre-reception data amount of the present invention.

  If it is determined in S31 that a VPN construction notification has not been received, it is determined in S44 whether a VPN switching notification has been received. The VPN switching notification is a notification transmitted from the router 6 in S15 of FIG. If it is determined that a VPN switching notification has been received, the process proceeds to S45. If it is determined that the VPN switching notification has not been received, the process proceeds to S31.

  In S45, the amount of data encrypted and communicated with the router 3 via the VPN is detected. This detection process is the process of S16 shown in FIG. Moreover, this detection process is the same process as S39. When the measured data amount is stored in the flash memory 12 as the communication data amount, the process proceeds to S46. In S45, the CPU 11 of the router 2 that detects the amount of data that is encrypted and communicated with the router 3 via the VPN is an example of the detection means of the present invention. In S45, the processing of the router 2 that detects the amount of data that is encrypted and communicated with the router 3 via the VPN is an example of the detection step of the present invention. The communication data amount stored in S45 is an example of the post-reception data amount of the present invention.

  In S46, it is determined whether or not the amount of data to be encrypted and communicated via the VPN established with the router 3 has decreased. This determination is made based on whether or not the communication data amount measured in S45 is smaller than the communication data amount measured in S39. If it is determined that the number has decreased, the process proceeds to S47. If it is determined that it has not decreased, the process proceeds to S45.

  In S47, the SAD is updated. The start point address or the end point address gives a switched flag to the SA that is the IP address of the router 3. Next, the switched flag is deleted from the SA to which the switched flag is assigned. As a result, the encrypted data from the router 2 to the router 3 is encrypted and communicated via the VPN constructed in S1 and S2 of FIG. When the switched flag is deleted and the update of SAD is completed, the process proceeds to S48.

  In S <b> 48, a switch completion notification is transmitted to the router 6 and the router 3. The switching completion notification transmission process is the same as S19 in FIG. When the switch completion notification is transmitted, the process proceeds to S31.

  The main process of the router 6 will be described with reference to FIG. This main process is executed by the CPU 11 of the router 6. The main processing program is stored in the flash memory 12. The main processing program is stored in a server (not shown) and transmitted to the router 6 in response to a download request from the router 6.

  In S51, the processing load is detected. The encrypted packet received by the router 6 in S3 of FIG. 5 is decrypted by the CPU 11 of the router 6. Next, the decrypted packet is encrypted by the CPU 11. This decryption and encryption conversion processing load is detected. When the detection of the processing load ends, the process proceeds to S52. The conversion process in which the CPU 11 of the router 6 decrypts and encrypts the received encrypted packet is the process of decrypting the data of the present invention and the conversion process of encrypting the data. The load imposed on the CPU 11 of the router 6 by this conversion processing is an example of the conversion processing load of the present invention. In S51, the CPU 11 of the router 6 that detects the processing load is an example of the relay device detection means of the present invention.

  In S52, it is determined whether or not the processing load is equal to or greater than a threshold value. If it is determined that the processing load is equal to or greater than the threshold, the process proceeds to S53. If it is determined that the processing load is less than the threshold, the process proceeds to S62. In S52, the CPU 11 of the router 6 that determines whether or not the processing load is equal to or greater than the threshold is an example of the relay device determination unit of the present invention.

  S53 to S55 are the same as S5 to S7 in FIG. In S53, the switching target is acquired, and this switching target is extracted from the SA to which the switched flag is not assigned. That is, when the construction information packet has already been transmitted to the router 2 and the router 3, the IP addresses of the two routers that are performing encrypted communication other than the encrypted communication between the two routers are extracted. . Therefore, one of the extracted IP addresses of the two routers may be the IP address of the router 2 or the router 3. Two routers having the extracted address are an example of another communication device of the first pair of the present invention. Two routers corresponding to data having the largest packet size for each of the two routers are selected as switching targets. As a result, the two routers having the start point address and the end point address extracted from the SA not assigned with the switched flag are encrypted by the router having the start point address and the end point address of the SA with the switched flag. It is a router that executes encrypted communication that causes a processing load having the second largest ratio of processing load due to communicated data. That is, the two routers having the extracted address are an example of another communication device of the second pair of the present invention. In S53, the CPU 11 of the router 6 that acquires the switching target is an example of the specifying unit of the present invention. The two routers extracted in the following description will be described as router 4 and router 5.

  In S54, PSK is generated. This PSK is different from the PSK transmitted to the router having the SA start point address and end point address to which the switched flag is assigned. If the two extracted routers are the router 4 and the router 5, in S55, the router 6 generates a construction information packet including the different PSK, the address of the router 4, and the address of the router 5 in the payload portion. When the generation of the construction information packet is completed, the process proceeds to S56. A construction information packet including a different PSK, an address of the router 4 and an address of the router 5 in the payload portion is an example of the third request notification of the present invention. Different PSK included in the construction information packet and the IP addresses of the router 4 and the router 5 are examples of the second construction information of the present invention.

  When the generation of the construction information packet ends, it is determined in S56 whether or not there is an encrypted communication that causes a significant increase in processing load. Specifically, it is determined whether or not the packet size of the encrypted communication of the two routers to be switched among the processing loads detected in S51 is 50% or more of the processing load detected in S51. If it is determined that it is 50% or more, it is determined that there is encrypted communication that causes a significant increase in processing load, and the process proceeds to S58. If it is determined that it is less than 50%, it is determined that there is no encrypted communication that causes a significant increase in processing load, and the process proceeds to S57.

  In S57, it is determined whether or not the packets that are encrypted and communicated by the two routers to be switched are only real-time packets. If it is determined that only the real-time packet is present, the process proceeds to S58. If it is determined that the packet is not only a real-time packet, the process proceeds to S59. When it is determined that the packet is not only a real-time packet, the router that performs encrypted communication with the router 6 through the VPN may determine whether there is a router other than the router to be switched. . In this case, if it is determined that there is a router other than the router to be switched, the process proceeds to S59. If it is determined that there is no router other than the router to be switched, the process proceeds to S58.

  In S58, a forced switching notification is given to the construction information packet created in S55. The forced switching notification is a notification that causes the router that has received the construction information packet to perform encrypted communication of all protocol data without using the router 6. If the encrypted communication of the router to be switched is not executed without going through the router 6, the processing load on the router 6 is not reduced, so a forced switching notification is given to the construction information packet. When the provision of the forced switching notification is finished, the process proceeds to S59.

  In S59, the construction information packet is transmitted to the two routers extracted in S53 via the VPN. When the two extracted routers are the router 2 and the router 3, the construction information packet is transmitted to the router 2 and the router 3 via the VPN constructed in S1 and S2. When the two extracted routers are the router 4 and the router 5, the construction information packet is transmitted via the VPN constructed with the router 4 and the VPN constructed with the router 5. When the transmission of the construction information packet is completed, the process proceeds to S60. In S59, the CPU 11 of the router 6 that transmits the construction information packet to the router 2 is an example of the relay device transmission means of the present invention.

  In S60, it is determined whether a construction completion notification has been received. If it is determined that the construction completion notification has been received, the process proceeds to S61. If it is determined that the construction completion notification has not been received, the process proceeds to S60.

  In S61, the SAD is updated. Since this process is the same as S11 shown in FIG. When the update of SAD is completed, the process proceeds to S51.

  If it is determined in S52 that the processing load is less than the threshold value, it is determined in S62 whether or not a switched flag is assigned to the SA. If it is determined that there is a switched flag, the process proceeds to S63. If it is determined that the switched flag is not given, the process proceeds to S51.

  In S63, a switching notification is transmitted. The switching notification transmission process is the same as the process of S15 of FIG. When the transmission of the switching notification is completed, the process proceeds to S64. In S64, it is determined whether a switching completion notification is received. If it is determined that the switching completion notification has been received, the process proceeds to S65. If it is determined that the notification of switching has not been received, the process proceeds to S64.

  In S65, the SAD is updated. This update process is the same as S20 in FIG. When the update of SAD is completed, the process proceeds to S51.

[Effect of the embodiment]
According to the router 2 of the present embodiment, when it is determined that the processing speed detected in S36 is less than the threshold, in S43, the CPU 11 of the router 2 performs encrypted communication of real-time packets via the VPN constructed in S1. It is determined that encrypted communication other than the real-time packet is performed via the VPN constructed in S32. Thereby, since the encrypted data other than the real-time packet is encrypted and communicated via the VPN constructed in S32, a decrease in the processing speed of the encrypted data other than the real-time packet is reduced. Further, since the CPU 11 of the router 2 performs encrypted communication of real-time packets via the VPN constructed in S1, the processing load on the router 6 is reduced. Accordingly, it is possible to reduce the communication delay of the encrypted communication of the real-time packet to the router 3 and the encrypted communication other than the real-time packet. In particular, the processing load of the router 6 is reduced by the amount that encrypted communication of encrypted data other than the real-time protocol is executed via the VPN established in S32. In a state where the processing load of the router 6 is reduced, the encrypted data of the real-time protocol that requires real-time property is encrypted and communicated through the VPN constructed in S1, so that encryption that requires real-time property is required. The communication delay of the digitized data can be reduced.

  According to the router 2 of the present embodiment, it is determined in S37 whether the processing speed of the process of encrypting or decrypting the dummy packet via the VPN constructed in S32 is equal to or higher than a threshold value. That is, it is determined whether or not the communication speed is equal to or higher than the threshold value in S36, and determining whether or not the processing speed is equal to or higher than the threshold value in S37 is a process of encrypting or decrypting data that is encrypted and communicated via the VPN. It is determined whether or not the communication speed including the processing speed is equal to or higher than the threshold value. As a result, it is determined whether or not the communication speed required for the encrypted communication via the VPN is equal to or higher than the threshold value. Therefore, the possibility that the processing load of the router 6 is reduced and the possibility that the communication delay of the encrypted data to the router 3 is reduced can be increased.

  According to the router 2 of the present embodiment, based on the time T2 received from the router 3, it is determined whether or not the communication speed exceeds the threshold value. As a result, it is determined whether or not the communication speed required for encrypted communication via the VPN is more than a threshold value. Therefore, the possibility that the processing load of the router 6 is reduced and the possibility that the communication delay of the encrypted data to the router 3 is reduced can be increased.

  According to the router 2 of the present embodiment, when the pre-reception data amount detected in S45 is smaller than the communication data amount detected in S39, the CPU 11 of the router 2 transfers from the router 2 to the router 3. The encrypted data of all protocols is encrypted and communicated via the VPN constructed in S1. Thereby, the processing load of the router 6 when encrypted data of all protocols is encrypted and communicated in S21 is smaller than the processing load of the router 6 in the state where the VPN construction notification is received in S8. Therefore, even if encrypted data of all protocols is encrypted and communicated in S21, the communication delay of the encrypted data to the router 3 can be reduced.

  According to the router 2 of the present embodiment, when it is determined in S56 that there is an encrypted communication that greatly contributes to the processing load, or in S57, the encrypted communication is performed between the router 2 and the router 3. When it is determined that the packet is only RTP, a forced switching instruction is included in the VPN construction notification. When it is determined in S40 that this forced switching notification is included in the VPN construction notification, the router 2 constructs a VPN with the router 3 again in S41. The reconstructed VPN uses an encryption algorithm whose encryption strength is lower than that when the encrypted data is encrypted and communicated via the VPN constructed in S32. As a result, a decrease in the processing speed of the encrypted data that is encrypted and communicated via the VPN constructed in S41 is reduced by an amount corresponding to a decrease in the encryption strength. Accordingly, even when encrypted data of all protocols is encrypted and communicated via the VPN constructed in S41, the communication delay of the encrypted data to the router 3 can be reduced.

  According to the encrypted communication system 1 of the present embodiment, if it is determined in S60 that the router 6 has received the construction completion notification, and it is determined in S52 that the processing load detected again is greater than or equal to the threshold, The construction information packet including the PSK, the address of the router 4, and the address of the router 5 in the payload portion is transmitted to the router 4 and the router 5 different from the router 3. Thereby, the communication delay of the encrypted data to the router 5 can be reduced in the encrypted communication process between the router 4 and the router 5 that have received the construction information packet. Along with the reduction of the communication delay, the processing load of the router 6 that has received the switch completion notification is further reduced. In particular, of the ratio of the processing load of the router 6, the processing load due to the encrypted communication between the router 4 and the router 5 is the second largest after the processing load due to the encrypted communication between the router 2 and the router 3. Since the encrypted communication between the router 4 and the router 5 that causes the next largest processing load is executed without the router 6, the processing load on the router 6 is further reduced.

[Modification 1]
The IP telephones 21, 31, 41, 51 may be smartphones, mobile phones, tablets, analog telephones, or the like. In the case of an analog telephone, the routers 2 to 5 may convert a signal from the analog telephone into digital data. This digital data constitutes a packet.

[Modification 2]
In the present embodiment, PSK is generated in the process of S6, but it is not necessary to newly generate PSK. In S6, the router 6 may generate a construction information packet including the IP addresses of the router 2 and the router 3, and the PSK used for authentication between the router 3 and the router 6 in the processing of S2. The router 6 encrypts this construction information packet and transmits it to the router 2 in S7. The router 2 transmits an ISAKMP SA generation request to the router 3 based on the IP address of the router 3 and constructs a VPN based on the PSK when the VPN is constructed between the router 3 and the router 6. Thereby, even if the router 6 does not transmit the construction information packet to the router 3, a VPN is constructed between the router 2 and the router 3. Further, the construction information packet including the PSK used for authentication in S1 and the IP address of the router 2 may be transmitted only to the router 3.

[Modification 3]
In the present embodiment, the PSK is associated with the IP address of the router and stored in each router. However, any information that identifies the router, such as FQDN (Fully Qualified Domain Name), may be used. When the phase 1 process is performed in the main mode, the hash value generated from the PSK is encrypted. Therefore, the information specifying the router is only the IP address. Therefore, when this IP address is a dynamic IP address, authentication cannot be performed. That is, when the IP address of the router is a dynamic IP address, information for specifying a router other than the IP address is used. Specific information such as FQDN may be used as information for specifying a router other than the IP address. Therefore, specific information such as FQDN is included in the construction information packet. When authentication is performed in the aggressive mode, the IP address may be a dynamic IP. If authentication is performed in the aggressive mode and the information for specifying the router is an IP address, the specific information such as FQDN may not be included in the construction information packet.

[Modification 4]
According to the router 2 of the present embodiment, when the communication speed is determined to be less than the threshold value in S36, or when the processing speed is determined to be less than the threshold value in S37, the VPN constructed in S1 is determined. It is determined that the encrypted communication of the real-time packet is performed via the VPN and the encrypted communication other than the real-time packet is performed via the VPN constructed in S32 or S41. That is, if it is determined in S36 that the communication speed is less than the threshold value, or if it is determined in S37 that the processing speed is less than the threshold value, data encryption according to TCP is performed via the VPN constructed in S1. Communication may be performed, and it may be determined that encrypted communication of data according to a protocol other than TCP is performed via the VPN constructed in S32 or S41. In this case, TCP is an example of a predetermined protocol of the present invention. Similarly, encrypted communication according to a protocol other than the real-time packet is performed via the VPN constructed in S1, and encrypted communication according to the protocol of the real-time packet is performed via the VPN constructed in S32 or S41. You may judge. It may be determined that encrypted communication of a predetermined protocol is performed via the VPN constructed in S1, and encrypted communication other than the predetermined protocol is performed via the VPN constructed in S32 or S41.

[Modification 5]
In the present embodiment, of the ratio of the processing load of the router 6 to the router 6, the router 4 and the router 5 that execute the encrypted communication that causes the processing load next to the processing load due to the encrypted communication between the router 2 and the router 3. However, the present invention is not limited to this, and two routers that perform encrypted communication via the router 6 may be the switching target.

[Modification 6]
It may be determined whether or not the communication speed defined by the time obtained by subtracting the time T0 from the time T5 in the process of S36 is equal to or higher than a threshold value. The time obtained by subtracting the time T0 from the time T5 defines a communication speed necessary for encrypted communication with the router 3 via the VPN. If this communication speed is equal to or higher than the threshold, the process proceeds to S38. If it is determined that the communication speed is less than the threshold, the process proceeds to S40.

1 Encrypted Communication System 2-6 Router 11 CPU
12 Flash memory 21, 31, 41, 51 IP phone 22, 32, 42, 52 PC

Claims (10)

A communication device connected to a relay device that relays encrypted communication and capable of communicating with the communication device of a communication partner via the relay device,
First construction means for constructing a VPN with the relay device;
VPN constructed by the first construction means, and first encrypted communication means for performing encrypted communication with the communication apparatus of the communication partner via the relay device;
When the processing load of the relay device becomes greater than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the communication device with the communication partner; Receiving means for receiving construction information for constructing a VPN from the relay device;
When receiving the first request notification by the receiving means, based on the construction information, a second construction means for constructing a VPN with the communication partner communication device;
Determining means for determining whether or not a communication speed required for data to be encrypted and communicated via the VPN constructed by the second construction means is equal to or higher than a threshold;
When the determination unit determines that the required communication speed is less than the threshold, the second communication unit performs encrypted communication with data other than the predetermined protocol via the VPN constructed by the second construction unit. An encrypted communication means,
The communication apparatus, wherein the first encryption communication unit performs encrypted communication of the data of the predetermined protocol when the determination unit determines that a necessary communication speed is less than a threshold value. The determination means determines whether or not the required communication speed including a processing speed of a process of encrypting or decrypting data encrypted and transmitted via the VPN constructed by the second construction means is equal to or higher than the threshold value. The relay apparatus according to claim 1, wherein the determination is made. The determination means obtains time information from the communication partner communication apparatus when the data transmitted to the communication partner communication apparatus via the VPN constructed by the second construction means is received by the communication partner communication apparatus. The relay apparatus according to claim 2, wherein the relay apparatus determines whether the necessary communication speed is equal to or higher than the threshold based on the received time information. The receiving means receives the first request notification including a forced switching instruction that is an instruction to perform encrypted communication of encrypted data of all protocols via the VPN constructed by the second construction means, and the judgment means When it is determined that the required communication speed is less than the threshold value,
The second construction unit reconstructs a VPN whose encryption strength is lower than the encryption strength of the VPN constructed by the second construction unit, with the communication device of the communication partner,
4. The communication apparatus according to claim 3, wherein the second encrypted communication means performs encrypted communication of data of all protocols via the VPN reconstructed by the second construction means. When the determination means determines that the required communication speed is less than a threshold value, the first encrypted communication means performs encrypted communication of real-time protocol data as the predetermined protocol, and the second encrypted communication means includes: The communication apparatus according to claim 1, wherein data other than the real-time protocol is encrypted and communicated as data other than the predetermined protocol. Detecting means for detecting a data amount of data encrypted by the second encrypted communication means;
After the first request notification is received, when the receiving unit receives a second request notification from the relay device that is a request for encrypted communication of data of all protocols by the first encrypted communication unit, The detection means detects a data amount before reception before the second request notification is received and a data amount after reception after the second request notification is received,
The first encrypted communication unit performs encrypted communication of data of all protocols when the amount of data after reception detected by the detection unit becomes smaller than the amount of data before reception. The communication device according to any one of 1 to 5. A computer connected to a relay device that relays encrypted communication and capable of communicating with the communication device of the communication partner via the relay device,
A first construction step of constructing a VPN with the relay device;
A VPN constructed in the first construction step, and a first encrypted communication step for performing encrypted communication with the communication device of the communication partner via the relay device;
When the processing load of the relay device becomes greater than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the communication device with the communication partner; A receiving step of receiving construction information for constructing a VPN from the relay device;
A second construction step of constructing a VPN with the communication apparatus of the communication partner based on the construction information when the first request notification is received in the reception step;
A determination step of determining whether or not a communication speed required for data to be encrypted and communicated via the VPN constructed in the second construction step is equal to or higher than a threshold;
When it is determined in the determination step that the necessary communication speed is less than the threshold value, the second communication unit performs encrypted communication of data other than a predetermined protocol with the communication apparatus of the communication partner via the VPN established by the second construction unit. An encrypted communication step, and
The program according to claim 1, wherein when the necessary communication speed is determined to be less than the threshold value, the first encrypted communication step performs encrypted communication of the data of the predetermined protocol. A method of a communication device connected to a relay device that relays encrypted communication and capable of communicating with the communication device of a communication partner via the relay device,
A first construction step of constructing a VPN with the relay device;
A VPN constructed in the first construction step, and a first encrypted communication step for performing encrypted communication with the communication device of the communication partner via the relay device;
When the processing load of the relay device becomes greater than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the communication device with the communication partner; A receiving step of receiving construction information for constructing a VPN from the relay device;
A second construction step of constructing a VPN with the communication apparatus of the communication partner based on the construction information when the first request notification is received in the reception step;
A determination step of determining whether or not a communication speed required for data to be encrypted and communicated via the VPN constructed in the second construction step is equal to or higher than a threshold;
When it is determined in the determination step that the necessary communication speed is less than the threshold value, the second communication unit performs encrypted communication of data other than a predetermined protocol with the communication apparatus of the communication partner via the VPN established by the second construction unit. An encrypted communication step,
An encryption communication method characterized in that, when it is determined in the determination step that a necessary communication speed is less than a threshold value, the first encryption communication step performs encrypted communication of data of the predetermined protocol. An encryption communication system comprising a communication device and a relay device that relays encrypted communication between the communication device and a communication device of a communication partner,
The communication device
First construction means for constructing a VPN with the relay device;
VPN constructed by the first construction means, and first encrypted communication means for performing encrypted communication with the communication apparatus of the communication partner via the relay device;
When the processing load of the relay device becomes greater than a threshold, a first request notification that is a request for encrypted communication without relaying the communication device with the communication partner and the communication device with the communication partner; Receiving means for receiving construction information for constructing a VPN from the relay device;
When receiving the first request notification by the receiving means, based on the construction information, a second construction means for constructing a VPN with the communication partner communication device;
Determining means for determining whether or not a communication speed required for data to be encrypted and communicated via the VPN constructed by the second construction means is equal to or higher than a threshold;
When the determination unit determines that the required communication speed is less than the threshold, the second communication unit performs encrypted communication with data other than the predetermined protocol via the VPN constructed by the second construction unit. Encrypted communication means;
The relay device is
A relay device detecting means for detecting a processing load including a conversion processing load of a process of decrypting encrypted data and a process of encrypting data;
Relay device determining means for determining whether the processing load detected by the relay device detecting means is equal to or greater than a threshold;
A relay device transmitting means for transmitting the first request notification and the first construction information to the communication device when the processing load is determined by the relay device determining means to be equal to or greater than a threshold;
With
When the determination means determines that the required communication speed is less than the threshold, the first encrypted communication means performs encrypted communication of the data of the predetermined protocol,
After the first request notification is transmitted to the communication device by the relay device transmission unit, the relay device determination unit determines again whether the processing load is equal to or greater than a threshold value,
When the relay device determining means determines again that the processing load is equal to or greater than the threshold value, the relay device transmitting means performs encrypted communication other than encrypted communication between the communication device and the communication device of the communication partner. A third request which is a request for causing at least one other communication device of the first pair of other communication devices to execute encrypted communication without relaying another communication device of the communication partner and the relay device. An encrypted communication system, characterized by transmitting a notification and second construction information for constructing a VPN with another communication device of the communication partner. The relay device detection means includes a processing load resulting from encrypted communication of the communication device and the communication device of the communication partner, out of a conversion processing load of a process of decrypting data and a process of encrypting data. A specifying unit that specifies another communication device of the second pair that executes encrypted communication that causes a large processing load;
The relay device transmitting means uses the second pair of other communication devices specified by the specifying means as the first pair of other communication devices, and sends the third request notification and the second construction information to the first pair. The encrypted communication system according to claim 9, wherein the communication is transmitted to at least one of the two pairs of other communication devices.