JP3821990B2 - Cryptographic communication method and system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, high-availability communication (communication that can be automatically continued by path switching even in the event of a failure, that is, communication with fault tolerance, the same applies hereinafter) and encryption communication (confidential communication using encryption technology, the same applies hereinafter) are simultaneously performed. The present invention relates to a cryptographic communication technique for enabling cryptographic communication to continue safely even when a configuration change of a communication relay device occurs during cryptographic communication and an optimum path changes in a network that can be realized.
[0002]
[Prior art]
The form of encryption communication performed using an IP (Internet Procotol) network is well known. This type of encryption communication is performed using a key (encryption key / decryption key) generated between the encryption device on the transmission side and the decryption device on the reception side. As communication forms in this case, there are an end-to-end encrypted communication form and a communication apparatus (hereinafter referred to as “encryption apparatus”) that encrypts and decrypts communication data, for example, packets on the communication path. There is a form in which encryption communication is performed by arranging them.
[0003]
As procedures for generating, exchanging, and setting keys used for encryption communication in an IP network, there are various methods such as an IKE (Internet Key Exchange) method. The transmission side encrypts the IP packet using the generated key (encryption key), and the reception side decrypts the packet using the key (decryption key) corresponding to the key.
[0004]
By the way, when a failure occurs in the optimum route during communication using the IP network, a routing protocol such as OSPF (Open Shortest Path First) is used, or a communication relay device such as a router itself Communication can be recovered by using the backup path setting function. That is, communication can be recovered by automatically setting a bypass route. The outline of these communication recovery methods will be described below.
[0005]
(1) When a routing protocol is used
As shown in FIG. 6, it is assumed that routers N11 to N15 are connected to nodes on the IP network between the communication device T11 and the communication device 12. The optimum route at the normal time is the communication device T11 → router N11 → router N12 → router N13 → router N15 → communication device T12, or vice versa. The routers N11 to N15 have their own route formation information, that is, each Information indicating which routers can communicate directly with each other is exchanged to form an optimum route between the networks.
[0006]
If a failure occurs in the router N13 on this optimum route, communication recovery is performed according to the following procedure.
First, a normal router adjacent to the router N13, for example, the router N12 detects that a failure has occurred in the router N13 by the function of the routing protocol. The detection method is determined by the routing protocol. The router N12 that has detected the failure notifies the adjacent routers N11 and N14 of information such as “the previous route could not be used” and “the link has been lost” by the function of the routing protocol. The notification information is also relayed to the adjacent router N15, thereby notifying all the routers in the routing domain (a group of routers that pass routing information). Thus, the route formation information held by each of the routers N11, N12, N14, and N15 is updated by the newly notified information, and a detour route that replaces the failure route, that is, the communication device T11 → router N11 → router N12 → router. The route of N14 → router N15 → communication device T12 is re-formed.
[0007]
(2) When using the backup path setting function
A router in the communication system shown in FIG. 6, for example, the router N12 has a backup path setting function, and when the router N12 detects that a failure has occurred in the relay path (presence of link or polling (monitoring signal), Based on the backup path setting function, the router N12 switches to a preset alternative path (backup path) and maintains communication based on the keep alive (signal for confirming that the line is not down). .
[0008]
[Problems to be solved by the invention]
Even when a failure occurs in the optimum route during the encryption communication as well as the normal communication, the detour route can be formed by using the function of the routing protocol and the backup route setting function. However, in the case of encrypted communication, the routing protocol function or the switching function to the backup path and the encrypted communication function are configured separately, so that an encrypted IP packet (encrypted) can be used with the existing mechanism. Data) cannot be decrypted, and encrypted communication may not be continued. This will be described below.
[0009]
Here, the configuration shown in FIG. 7, that is, the communication device T11 is connected to the router N12 via the encryption device M21, the communication device T22 is connected to the router N15, and the encryption is performed between the router N12 and the router N15. Assume an IP network configuration in which the devices M22 and M23 are connected in parallel.
[0010]
The routers N12 and N15 and the encryption devices M21 and M22 exchange path formation information held by each other to form an optimum path between networks. The optimum route at normal time, that is, the route when converged by the normal route, is communication device T11 → encryption device M21 → router N12 → encryption device M22 → router N15 → communication device T12, and encryption device M21 is connected from communication device T22. The transmitted packet is encrypted using a key (for example, key A) used between the own device and the encryption device M22.
[0011]
In this state, some failure occurs in the encryption device M22, the route is changed by the function of the routing protocol, and the optimum route is changed from the communication device T11 → the encryption device M21 → the router N12 → the encryption device M23 → the router N15 → the communication device T12. Suppose that it was changed automatically. In this case, the key (for example, key B) used between the encryption device M21 and the encryption device M23 is different from the key A described above. However, since the encryption device M21 does not change the packet transmission destination (communication device T12), the encryption key for data transmitted from the communication device T11 to the communication device T12 should be changed from the key A to the key B. It cannot be recognized from the conventional routing protocol. Therefore, the packet is encrypted with the key A by the encryption device M21, and cannot be decrypted by the encryption device M23 using the key B, so that the encrypted communication cannot be recovered after all.
[0012]
In encrypted communication, the IP header including the address of the transmission destination and the data portion (that is, the payload) of the packet are encrypted together, and the communication is performed with the IP header including the address of the new transmission destination (decryption device). There is a tunnel mode and a transport mode in which only the data part of the packet is encrypted without encrypting the destination address. In any mode, when a failure occurs in the encryption device M22 as described above, The encryption device M21 cannot recognize the necessity of key change.
[0013]
Such a problem occurs not only when a path failure occurs during encryption communication, but also when a router, encryption device, communication device, etc. are newly added to the location (node) that has been the optimal route until then, This also occurs in common when some of the routers move. This is because the arrangement of routers and the like in this type of conventional highly available communication is fixed, and the key used for encryption communication is also fixed.
[0014]
Therefore, the present invention dynamically changes the encryption key even when there is a change in the arrangement of the devices that perform encryption and decryption in a network in which high availability communication and encryption communication can be realized simultaneously. Therefore, the main issue is to provide a technology that allows encryption communication to continue safely.
[0015]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an improved encryption communication method, encryption communication system, communication relay device, and recording medium suitable for realizing the communication relay device by a computer.
[0016]
The encryption communication method of the present invention is a method for performing high availability communication and encryption communication via a network that can be realized simultaneously, and includes predetermined information including arrangement information regarding the arrangement of communication relay apparatuses capable of encryption communication on the network. Exchange information among the plurality of communication relay devices to form an optimum route on the network, and perform encrypted communication of communication data between the communication relay devices existing on the optimum route, and When the configuration of the communication relay device in the network is changed, the route formation information is updated to re-form a new optimum route, and mutual agreements are established between the communication relay devices capable of encryption communication existing in the re-formed optimum route. The encryption communication is continued using a key. Each communication relay device records the identification information of the communication device or network when the encrypted communication data destined for the certain communication device or network can be decrypted, and receives the route formation information from the other communication relay device. When the encryption communication destination holds the same identification information as the identification information at the time of receipt, the key is negotiated with the other communication relay device.
[0017]
The cryptographic communication system of the present invention forms an optimum path on a network that can simultaneously realize high availability communication and cryptographic communication by exchanging predetermined path formation information between a plurality of communication relay apparatuses, This is a cryptographic communication system that performs cryptographic communication of communication data between communication relay devices existing on the optimum route. The route formation information of each communication relay device includes arrangement information related to the arrangement of communication relay devices capable of cryptographic communication on the network, and at least one of the plurality of communication relay devices is on an optimum route during cryptographic communication. The communication relay device is configured to notify the other communication relay device of the changed layout information when it is detected that the configuration of the communication relay device has been changed, and at least the other one is based on the notification. Update the own route formation information to re-form a new optimum route and continue the encryption communication using a mutually agreed key between the communication relay devices capable of encryption communication existing in the re-formed optimum route. It is comprised as follows.
[0018]
The communication relay device of the present invention forms an optimum route for communication data on a network based on predetermined route formation information and performs communication for encryption communication with other communication relay devices existing on the optimum route. In the apparatus, the route formation information includes arrangement information regarding the arrangement of the communication relay apparatus capable of encryption communication, and when another communication relay apparatus serving as a communication partner becomes incapable of communication during encryption communication, Means for updating the contents of the arrangement information included in the route formation information, means for forming a new optimum route based on the updated route formation information, and encryption communication on the newly formed optimum route is possible And a means for detecting another communication relay device, wherein the encryption communication is continued using a key negotiated with the detected communication relay device.
[0019]
More specifically, the route formation information is information exchanged with other communication relay devices based on a predetermined routing protocol, and is information regarding the arrangement of nodes that can perform encrypted communication and the nodes are encrypted. It includes identification information of a communication path to be subjected to communication, and the key is negotiated based on this identification information. If the key negotiated with the node having the identification information is held in advance, the key is searched, and if the key is not held, the key is generated with the node to secure the key. To do.
[0020]
The update means in the communication relay device deletes the arrangement information related to the communication relay device that has become unable to communicate during the encrypted communication, and the arrangement information related to the communication relay device added during the encrypted communication. If there is a communication relay apparatus that has been moved during encrypted communication, the arrangement information related to it is corrected.
[0021]
The recording medium provided by the present invention is on a network capable of simultaneously realizing high availability communication and encryption communication based on predetermined route formation information including arrangement information regarding the arrangement of communication relay apparatuses capable of encryption communication. The function of forming the optimum route, the function of performing cryptographic communication with the communication partner device, and updating the contents of the arrangement information included in the own route formation information when the configuration of the communication partner device is changed A function to form a new optimum route based on the updated route formation information and to continue cryptographic communication using a key determined with another communication partner device existing in the new optimum route Is a computer-readable recording medium on which program codes for forming the above are recorded on a computer.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the present invention, in a network that can simultaneously realize high availability communication and encryption communication, when encryption communication is performed between devices that transfer route formation information according to a routing protocol, information on the arrangement of devices that can perform encryption communication Is included in the route formation information, and the route formation information is linked to the information related to the key change.
For example, in the case of a link state type routing protocol, on which link the device capable of cryptographic communication is arranged and where the cryptographic communication can be performed, and in the case of a distance vector type routing protocol, in the distance vector In the path formation information, which router is present in Then, when transmitting the encrypted data, a key corresponding to the receiving encryption apparatus is used, and if there is no corresponding key, a new generation can be easily performed.
In addition, the method generally used conventionally can be utilized for use / generation of a key.
[0023]
The above-described encryption communication method can be implemented by, for example, an encryption communication system configured as shown in FIG.
The cryptographic communication system 1 includes a transmission side communication device T11 arranged on an α network, a reception side communication device T12 arranged on a β network, and a plurality of routers interposed between these communication devices, that is, an A router. It includes L11, D router L12, B router L13, C router L14, and other network components, and is configured to realize high availability communication and encryption communication at the same time.
It is assumed that the α network and the β network are connected via a wide area communication network such as the Internet.
[0024]
Each of the routers L11 to L14 is a kind of computer having a memory and a CPU, and functions of a routing protocol formed by the CPU reading and executing a program code recorded on a predetermined recording medium, and encryption communication. A function and a function for linking these functions. The recording medium on which the program code is recorded is a fixed recording medium such as a semiconductor memory that can be read by the CPU, for example, when mounted on the router, but is distributed through a portable recording medium such as a CD-ROM and is mounted at the time of mounting. It may be installed on the fixed recording medium.
The routing protocol function is basically the same as that of the conventional router, but the following two information is included in the route formation information exchanged with other routers by the routing protocol, and the cryptographic communication function is linked. This is different from the functions of a conventional router.
(1) Node (router) placement and interface ID that can perform encrypted communication
Example: “There is an A router at the A node that can perform encrypted communication.”
(2) Communication path ID for which the node performs encryption communication
Example: “Cryptographic communication target (communication path ID) in router A is for α network and γ network communication”
The data format corresponding to these pieces of information is adapted to the applicable network protocol and routing protocol. For example, in the case of OSPF of an IP network, the information is included in an LSA (Link State Advertisement) described later.
[0025]
On the other hand, with respect to the function of encryption communication, each router performs encryption communication as follows.
(1) Encrypt communication data, for example, a packet and generate encrypted data for communication corresponding to the communication path ID to be subjected to encryption communication.
Example: “A packet whose source address belongs to the γ network and whose destination address belongs to the β network is a target of encryption communication because the destination address matches the communication path ID” (2 ) If the encryption key is stored in advance for the node having the communication path ID corresponding to the communication path, it is retrieved and used. When the key is not held, the key is secured by generating a key with the node (router).
Example: “There is a router that can perform cryptographic communication called a B router on the route from the A router to the β network, and that the B router is the subject of the cryptographic communication to the β network. The router knows, so we encrypt the packet that was the subject of the encrypted communication using the key corresponding to the B router. "
A function for linking both functions will be described later.
[0026]
In addition, although it is desirable that all the routers L11 to L14 are provided with the above functions, only the router that acts centrally that encrypts and relays the packet transmitted from the communication device T11 is provided. Even so, the present invention can be implemented.
[0027]
Next, the communication form by the encryption communication system 1 of this embodiment is demonstrated. Here, as shown in the figure, the network address between the communication device T11 in the α network and the A router L11 is “163.135.10.0/24”, and between the communication device T12 in the β network and the B router L13 or the C router L14. Interface address of the A router L11 is “163.135.100.10”, the interface address of the B router L13 is “163.135.200.20”, and the network address of the C router L14 is “163.135.300.30”. An example in which cryptographic communication is performed by improving the OSPF, which is a representative of the link state routing protocol, will be described. The OSPF is described in detail in specifications RFC2328, RFC1131, and STD0054 issued by the international organization IETF.
[0028]
FIG. 2 shows a format example of the router link LSA transmitted by each of the routers L11 to L14 in the path formation information used in OSPF, that is, the link state advertisement packet (LSA).
This router link LSA is various link information passed between adjacent routers, and is composed of a link status header and an LSA part. In the LSA part, router type, link ID, link data, etc. are described, and each router can recognize information related to the arrangement of other routers by the information described in this, and use it for route calculation or recalculation. Will be able to. FIG. 3 shows the contents of the router type, the link ID corresponding to it, and an example of link data. Types 1 to 4 are information included in an existing router, and type 5 is information added in the present embodiment, that is, information related to encrypted communication. This type 5 description makes it possible to know which router is performing cryptographic communication and where. In type 5, when the link data is Null, it indicates that encrypted communication can be performed with somewhere that has not yet been determined.
[0029]
The LSA can transmit a plurality of pieces of link information that can be held by the routers L11 to L14. Therefore, if one router performs encrypted communication with a plurality of routers, a plurality of encrypted communication LSAs can be designated. For example, if the link ID is “163.135.100.10” and the link data is “163.135.20.0/24” in the type 5 LSA, the router having “163.135.100.10” as the address that transmitted this LSA is “163.135. Indicates that encryption communication is possible with the other party having the address “20.0 / 24”. Furthermore, if the link ID is the same and there is an LSA with link data “163.135.30.0/24”, the router “163.135.100.10” must be able to perform encrypted communication with the other party of “163.135.30.0/24”. Indicates.
[0030]
When such an improved OSPF is used to encrypt and transmit a packet, each of the routers L11 to L14 declares information on the encrypted communication destination using LSA. This declaration also includes information on the encryption communication source. When each of the routers L11 to L14 can decrypt a packet destined for a certain network, the information on the network is recorded as “encrypted communication handling network (or host)” in the router's own database. This information is used to generate a key with each LSA source router when each router has the same "encryption communication network" as the encryption communication destination when receiving the encryption communication LSA of another router. It becomes information necessary to do.
[0031]
Each router exchanges a Hello packet (such as a keep alive signal to an adjacent router), and between the routers that can deliver the packet, its own LSA is transmitted to the other side on a link-by-link basis. It is like that. For example, when the B router L13 and the C router L14 are routers that can be encrypted and decrypted, the fact and that they are operating normally are transmitted to the A router L11 through the D router L12. The A router L11 learns from the LSA of the B router L13 that the router L13 is ready to perform cryptographic communication with its own “cryptographic communication network”, and generates a key for encryption with the B router L13. Implement the process. This process may be a commonly used key generation process. The A router L11 also performs a process of generating a key with the C router L14.
[0032]
FIG. 4A is a diagram showing the contents of the link table (original information of the routing table) of the A router L11 when it converges on the normal route. In the example shown in the figure, the A router L11 is linked to the α network and the D router L12, and the cryptographic communication networks are α and γ. The B router L13 and the C router L14 are linked to the β network and the D router L12, and the “encryption communication handling network” is β. The D router is linked to the A router L11, the B router L13, and the C router L14, and there is no designation of "encryption communication handling network" or somewhere that has not been determined yet. Note that the “encryption communication handling network” does not necessarily have to be adjacent.
[0033]
From this link table, the A router L11 indicates the optimum route from the network α to the network β as α network (communication device T11) → A router L11 → D router L12 → B router L13 → β network (communication device T12). To form.
[0034]
On the other hand, the A router L11 sets the encryption filter as shown in FIG. 5A in cooperation with the link table of FIG. That is, the “encryption communication handling network” of the A router L11 is the α network, and the router having β as the “encryption communication handling network” on the path is the B router L13. Therefore, the A router L11 generates a key a with the B router L13 (if the key a is already held, it searches for it). The meaning of this link table is “a packet (α → β) whose source address (network) is α and destination address (network) is β is encrypted with the key a and transmitted to the B router L13 (set peer ( B)) Let's do it. As a result, encrypted communication using the key a becomes possible.
[0035]
Here, consider a case where a failure occurs in the B router L13.
In this case, since the LSA issued by the B router L13 does not reach the D router L12 and the A router L11, the A router L11 uses the routing protocol function to restore the path assuming that the B router L13 cannot be used. FIG. 4B is a diagram showing the content after updating the link table (source of the routing table) of the A router L11 when it converges on the recovery path. As shown in the figure, the link information of the B router L13 is lost. From this link table, the optimum route is changed as α network (communication device T11) → A router L11 → D router L12 → C router L14 → β network (communication device T12). In cooperation with the route change, the key a used by the A router L11 is dynamically changed to the key c.
[0036]
That is, when the link table in FIG. 4B is updated, the A router L11 updates the content of the encryption filter as shown in FIG. That is, since it is understood that the router having β as “encryption communication handling network” on the path is the C router L14, the A router L11 generates the key c with the C router L14 (the key c has already been set). If so, find it). The meaning of this link table is “a packet (α → β) having a source address (network) of α and a destination address (network) of β is encrypted with a key c and transmitted to the C router L14 (set peer ( B)) Let's do it.
[0037]
As described above, even when a failure occurs in the B router L13 and the route is changed, the encryption filter setting as shown in FIG. 5B is obtained from the link table based on the updated routing protocol. Since the key is changed, encrypted communication can be continued.
[0038]
In this embodiment, it is assumed that a route failure due to a router failure or the like has occurred as an example of a case where a change occurs in the arrangement configuration of a router capable of encrypted communication and a key to be used is changed. The present invention is not limited to such an example. For example, the present invention can be applied to a case where a key to be used is changed as a result of adding a router on a network or moving a router from one network to another network. Is possible. In other words, without setting the encryption communication manually, the routing protocol function is used to pass the route formation information to each other, the placement information is updated at each router, and the optimum route is automatically formed, thereby enabling the encryption. Communication can be continued. In addition, it is possible to automatically find a partner device for performing encrypted communication by simply specifying a target network or host for performing encrypted communication in the route formation information of the router.
These functions are in line with the actual communication mode in which the number of routers connected to a network constantly increases and decreases, which makes it possible to easily cope with the spread of mobile communication. .
[0039]
In this embodiment, a router has been described as an example of a communication relay device. However, the mechanism of the present invention can be applied to all devices in which the other party of encryption communication may change. Further, as in the present embodiment, it is preferable to provide a function for exchanging path formation information with another apparatus and a function for dynamically changing the encryption key in one apparatus (for example, a router). There is, but it does not always have to be in this form. For example, configuring the communication device connected to the router to have a function of dynamically changing the encryption key based on the notification from the router is an obstacle to the implementation of the encryption communication method of the present invention. Must not.
[0040]
In the present embodiment, an example in which an IP network is used as a communication medium has been described. However, the present invention can be applied to any network that can simultaneously realize highly available communication and encrypted communication regardless of the scale. It can also be used on intranets and extranets that are unsecured networks.
[0041]
Since the application of the present invention is premised on the mutual transfer function of route formation information such as a routing protocol, an ISP (Intarnet Service Provider) that uses another unique routing protocol or cannot connect the routing protocol is used. When it is used, it is used in a closed network that does not use the ISP, but even when the ISP is used, the route formation information is relayed by a known tunneling technique in a method that does not depend on the ISP service. By doing so, it is possible to use the network beyond the closed network.
[0042]
The present invention is particularly effective when the encryption communication destination is frequently changed physically or logically, and can flexibly cope with a network configuration change such as a mobile network.
[0043]
The present invention can also be applied to the consumer cryptocommunications market (a form of using network services for individuals). Currently, SSL (Secure Socket Layer) is the mainstream of encryption communication technology for individuals. This is an encryption in the upper layer of communication, and the purpose is to perform end-to-end encrypted communication by encrypting and transmitting communication data by the terminal (communication device) operated by the individual himself / herself. . Applying the present invention to a network accessed by a terminal (including a mobile terminal) operated by an individual can be an effective means for promoting the network service.
[0044]
【The invention's effect】
As is clear from the above description, according to the present invention, even if a device is changed, that is, when a key is changed as a result of a path change during the encryption communication, the encryption communication can be performed safely and securely. There is a unique effect of being able to continue with certainty.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a cryptographic communication system to which the present invention is applied.
FIG. 2 is a diagram showing a format example of a router link LSA.
FIG. 3 is a diagram showing the type of router link LSA.
4A is a diagram for explaining the contents of a link table used when an optimum route is formed using a routing protocol, and FIG. 4B is a diagram for explaining the contents of a link table updated when a failure occurs.
FIG. 5A is a diagram showing the setting content of an encryption filter during normal operation, and FIG. 5B is a diagram showing the setting content of the encryption filter updated when a failure occurs.
FIG. 6 is a network configuration diagram for use in explaining the optimum route restoration when a routing protocol is used in the prior art.
FIG. 7 is a network configuration diagram for use in explaining the optimum route restoration in the case of using a conventional routing protocol and encrypted communication.
[Explanation of symbols]
1. Cryptographic communication system
T11, T12 communication device
L11-L14, N11-N15 router
M21 to M23 cryptographic device

Claims (10)

An encryption communication method for performing high availability communication and encryption communication through a network capable of realizing simultaneously,
An optimum route on the network is formed by exchanging predetermined route formation information including arrangement information on the arrangement of the communication relay device capable of encryption communication on the network between the plurality of communication relay devices. Performs encrypted communication of communication data between existing communication relay devices, and when the configuration of the communication relay device on the network is changed, updates the route formation information to re-form a new optimum route and re-form Characterized in that the encrypted communication is continued using a mutually agreed key between the communication relay devices capable of encrypted communication existing in the optimal path,
Cryptographic communication method. Each communication relay device records the identification information of the communication device or network when the encrypted communication data destined for the communication device or network can be decrypted, and the route formation information from other communication relay devices. When the encryption communication destination holds the same identification information as the identification information when receiving the key, the key is negotiated with the other communication relay device,
The encryption communication method according to claim 1. By exchanging predetermined path formation information among multiple communication relay devices, an optimal path on the network that can simultaneously realize highly available communication and encrypted communication is formed, and communication relay existing on this optimal path An encryption communication system that performs encrypted communication of communication data between devices,
The route formation information of each communication relay device includes arrangement information regarding the arrangement of communication relay devices capable of cryptographic communication on the network,
When at least one of the plurality of communication relay apparatuses detects that the arrangement configuration of the communication relay apparatus on the optimum route during encrypted communication is changed, the changed arrangement information is transmitted to another communication relay apparatus. It is configured to notify, and at least the other one can update its own route formation information based on the notification to re-form a new optimum route and can perform encrypted communication existing in the re-formed optimum route It is configured to continue the encryption communication using a key mutually agreed between communication relay devices,
Cryptographic communication system. Forms an optimal route on the network that can simultaneously realize highly available communication and encrypted communication based on predetermined route formation information, and performs encrypted communication with other communication relay devices existing in the optimal route. A communication relay device to perform,
The route formation information includes arrangement information related to arrangement of a communication relay device capable of encrypted communication,
Updating means for updating the content of the placement information included in its own route formation information when the placement configuration of another communication relay device in the optimum route is changed during encrypted communication;
Route formation means for forming a new optimum route based on the updated route formation information;
Detecting means for detecting another communication relay device capable of encrypted communication on the newly formed optimum path,
The cryptographic communication is continued using the key negotiated with the detected communication relay device,
Communication relay device. The path formation information is information exchanged with other communication relay devices based on a predetermined routing protocol, and information regarding the arrangement of nodes that can perform cryptographic communication, and the nodes that are subjected to cryptographic communication Including identification information of a communication path to be performed, and determining the key based on the identification information,
The communication relay device according to claim 4. If the key negotiated with the node having the identification information is held in advance, the key is retrieved, and if the key is not held, the key is generated by performing key generation with the node. It is characterized by securing,
The communication relay device according to claim 5. The update unit is characterized by updating so as to delete the arrangement information related to the communication relay device that has become unable to communicate during encrypted communication.
The communication relay device according to claim 4. The update means updates to add arrangement information related to a communication relay device added during encrypted communication,
The communication relay device according to claim 4. The update means updates the arrangement information related to the communication relay apparatus moved during the encrypted communication so as to be corrected.
The communication relay device according to claim 4. A function for forming an optimum route on a network network that can simultaneously realize high-availability communication and encryption communication based on predetermined route formation information including arrangement information regarding the arrangement of communication relay devices capable of encryption communication;
A function for performing encrypted communication with a communication partner device;
When the configuration of the communication partner device is changed, the content of the arrangement information included in its own route formation information is updated, and a new optimum route is formed based on the updated route formation information. A computer-readable recording medium on which a program code for forming on a computer a function for continuing encryption communication using a key determined with another communication partner device existing in a new optimum path is recorded .

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