JP2003348072A - Method and device for managing encryption key in autonomous distribution network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance security by achieving encryption communication in communication between different autonomous distribution networks in a system for connecting a plurality of autonomous distribution networks. <P>SOLUTION: This management method includes: a method (608) for sharing a key for key distribution by performing authentication among key management devices 101, 102, 103 of the respective autonomous distribution networks when autonomous distribution networks 109, 111 are connected with a host autonomous distribution network 108 for connecting autonomous distribution networks together; a method (617) for preliminarily inquiring (605) whether or not an applicable encryption key exists in the key management device 101 of other autonomous distribution network 109 when the encryption key is issued in the local autonomous distribution network 111, for issuing the key when the key exists (610) and for generating and issuing the key by the key management device 103 by which the inquiry is made when the key does not exist (618); and a method for periodically updating the key by the device issuing the key and for transmitting a key update request to the key management devices of other autonomous distribution networks as well. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autonomous distributed network based on broadcast communication and an autonomous distributed network for maintaining communication security in a system constituted by connecting a plurality of autonomous distributed networks. The present invention relates to a method and apparatus for managing an encryption key in a computer.

[0002]

2. Description of the Related Art Broadcasting for simultaneously transmitting a message to an entire network is performed at the second layer of Ethernet (registered trademark), and at IP (I).
This is performed in a third layer such as the Internet Protocol. And usually, a special destination address for broadcasting is specified,
Sent. An example of using broadcast is DH
CP (DynamicHost Configurat)
The client that receives the assignment of the TCP / IP parameters using this first performs a broadcast to search for a DHCP server.

[0003] When broadcasts occur frequently, they occupy a large amount of network traffic, and the overall transmission efficiency is reduced. Therefore, in a large-scale network, a router is used to divide the network into a plurality of broadcast domains. Since routers do not relay broadcasts, they are used to divide the broadcast domain.

An autonomous decentralized system (ADS: Automo
us DecentralizedSystem)
By sending only data from the sending side and broadcasting without attaching an address, the receiving side determines whether it is its own data, if so, performs reception processing, and discards if not relevant It is a communication system.

[0005] Actually, it is used in a subscriber system using an optical fiber. That is, instead of individually installing optical fibers from the subscriber line accommodating station to individual user homes, optical fibers are distributed in the form of a star by an optical branching device (RT) on the way. Therefore, communication is multiplexed between the subscriber line accommodation station and the optical branching device. Since the subscriber line accommodating station and the optical branching device have a two-stage star structure, they are named double star.

[0006] In such an autonomous decentralized network, security technology is an important issue because all users connected to the transmission side can receive transmission data. Security technologies in autonomous distributed networks include, for example,
Ishida: “Study of Security Tech
nikes in the Vehicle-Roa
d Communications System ”,
8th World Congress on Int
elligent TransportSystem
s, 2001.10 (hereinafter referred to as the previous proposal).

[0007]

The proposed system is a system constituted by a single autonomous decentralized network,
Alternatively, 1 for the entire system to which multiple autonomous distributed networks are connected.
It is assumed that a system in which two key management devices are installed. For this reason, each has a device for key management,
The method of distributing and updating cryptographic keys in a system that connects different autonomous distributed networks is not specified.

Accordingly, an object of the present invention is to solve such a conventional problem, and to provide a system for connecting different autonomous distributed networks each having a key management device, in communication over different autonomous distributed networks. To realize cryptographic communication, implement key distribution methods and updating methods that allow the same cryptographic key to be shared between different autonomous distributed networks, as well as authentication methods and cryptographic communication methods that are the premise of their realization. An object of the present invention is to provide an encryption key management method and apparatus in an autonomous distributed network.

[0009]

In order to achieve the above object, a method for managing an encryption key in an autonomous distributed network according to the present invention comprises:
In an autonomous decentralized network connecting multiple autonomous decentralized networks, when a key is issued in a local autonomous decentralized network in order to realize the same encryption key sharing between the autonomous decentralized networks, the key of another local autonomous decentralized network is used. The management device inquires whether the encryption key is already registered, and generates a new encryption key only when the encryption key does not exist. The management device that generates the encryption key updates the key with respect to the corresponding key. It becomes. Hereinafter, for simplicity, an autonomous distributed network connecting a plurality of autonomous distributed networks is referred to as an upper autonomous distributed network, and each autonomous distributed network connected by the upper autonomous distributed network is referred to as a local autonomous distributed network.

[0010] The key management device of the local autonomous distributed network connected to the higher autonomous distributed network distributes random numbers to key management devices of other local autonomous distributed networks connected to the higher autonomous distributed network, and performs authentication. And registers the key distribution key of the key management device determined to be valid based on the authentication result. Conversely, the key management devices of the other local autonomous distributed networks connected to the higher autonomous distributed network also distribute random numbers to the key autonomous distributed network key management devices connected to the higher autonomous distributed network and perform authentication. Then, the key distribution key of the key management device determined to be valid based on the result of the authentication is registered.
According to the above method, the key management devices connected to the upper autonomous decentralized network can share each other's key for key distribution.

When a device in the local autonomous distributed network managed by the key distribution device requires an encryption key, the device in the local autonomous distributed network queries the key management device for the encryption key. When receiving the inquiry about the encryption key, the key management device distributes the encryption key if the encryption key already exists,
If there is no corresponding encryption key, it inquires of a key management device of another local autonomous distributed network whether there is a corresponding key, and if there is no corresponding key, a new encryption key is generated and issued. The key management device that has issued the key is a device that periodically updates the key in question, and when updating the key, the key management device of the other local autonomous distributed network is also required to update the key. Send an update notification.

According to the above method, the same encryption key can be shared by a plurality of autonomous distributed networks connected by a higher-order autonomous distributed network, and cryptographic communication in communication between different autonomous distributed networks becomes possible.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a network in which a plurality of autonomous distributed networks are interconnected according to an embodiment of the present invention. In the present embodiment, a system is assumed in which base stations 104, 105, and 106 that perform wireless communication with a traveling vehicle are connected by an autonomous distributed network. In FIG. 1, nothing is described in the local roadside network 110, but a base station or the like is connected as in the other cases. The autonomous decentralized network connecting the base stations is called a roadside network. That is, ITS
(Intelligent Transport Sy
In the case of “stem”, a communication network is wired on the side of the road.

The base stations 104, 105, and 106 are connected to the local roadside networks 109, 110, and 111 every several to tens of stations.
And a plurality of local roadside networks 109, 110, 11
1 is connected to the upper road side network 108. The local roadside networks 109, 110, 111 have gateways 101, 102, 103 and base stations 104, 10 respectively.
5, 106 and the local server 107 are connected. The local roadside network and the upper roadside network are distributed autonomous networks (ADS), and communication within each roadside network is broadcasted.
The receiving side determines whether or not to receive.

Hereinafter, the description of transmitting data within the roadside network basically means that the data is broadcasted within the roadside network. The gateway is connected to both the local roadside network and the upper roadside network, and bridges each roadside network.
In this embodiment, the gateway 101 is connected to the upper roadside network 108.
And the local roadside network 109, and the gateway 102
Connects the upper roadside network 108 and the local roadside network 110,
The gateway 103 is connected to the upper road network 108 and the local road network 111. The local server is treated the same as the base station in terms of key management, and therefore, will not be described below. In the autonomous decentralized network, a key management device is set, and when a new device is connected to the autonomous decentralized network, authentication is performed between the key management device and the newly connected device. It manages distribution of necessary encryption keys and regular updates of encryption keys.

FIG. 2 is a schematic configuration diagram of the gateway device in FIG. As shown in FIG. 2, the gateway device of the present embodiment includes a CPU 201, an input device 202,
It has an output device 203, a communication device 204, and a memory 205. The CPU 201 is a device that controls the operation of the entire gateway device. The memory 205 is a storage device that loads various programs and data for controlling the operation of the entire gateway device. The input device 202 is a device that inputs setting information such as a key to the gateway device, and inputs a road-side network management command such as execution of a key update.

The output device 203 is a device that performs various outputs associated with management, such as the status of the gateway and the roadside network. The communication device 204 is a device that communicates with another processing device via an upper roadside network, a local roadside network, or another connected network. In FIG. 2, a connection a to the upper roadside network, a connection b to the local roadside network, and a connection c to other processing devices are provided. The gateway device includes an authentication processing unit 206 for performing authentication, an encryption processing unit 207 for performing encryption, and a key issuing processing unit 20 for issuing a key.
8, a key update processing unit 209 for updating a key, and a key search processing unit 210 for searching for a key from a table.
These are all processed by a program.

Also, an encryption key table 211 for storing an encryption key used for own communication, a key transmission key table 212 for storing a key distribution public key of another base station or gateway used for key transmission, Key distribution key table 2 for storing information on keys distributed to base stations and the like in the local roadside network
13 are provided.

FIG. 3 is a sequence chart of a process in which a device connected to the upper road side network authenticates another device. Here, a process in which the gateway 103 authenticates the other gateways 101 and 102 connected to the upper roadside network when the gateway 103 is newly connected to the upper roadside network 108 is shown. The upper frame in FIG.
, The transmission of the signature, the signature key, the key distribution key, and the registration process by the gateway 103. The lower frame shows the transmission of the signature, the signature key, the key distribution key by the gateway 102, and the registration process by the gateway 103.

When the gateway newly connects to the upper road side network 108 (301), the gateway 103 generates a random number.
(302), and transmits it to the upper road side network 108 (303). As described above, since the communication in the roadside network is broadcast, a random number is transmitted to all gateways in the upper roadside network. The gateway 101 that has received the random number creates a signature for the random number using the signature private key of the gateway (304), and transmits the created signature, signature public key, and key distribution public key (305). The gateway 103 newly connected to the upper road side network 108 receives the signature, and verifies the signature using the signature public key (306).

It is assumed that a certificate is attached to the signature public key transmitted from the gateway 101, and the received gateway 103 verifies the certificate.
If the signature verification is successful, the key distribution public key of the gateway 101 that created the signature is registered (307). On the other hand, it is assumed that the certificate is also attached to the key distribution public key transmitted from the gateway 102, and the received gateway 103 verifies the certificate. Other gateways connected to the roadside network perform the same processing on the random numbers (308 to 311). As described above, the upper roadside network 1
The gateway 103 newly connected to 08 confirmed the validity of the other gateways 101 and 102 on the roadside network, and was able to obtain a key for distributing the encryption key to the other gateways. When signing a random number, a method of preventing the replacement of the public key by including the public key as a signature target is also conceivable.

FIG. 4 is a sequence chart of a process in which a device connected to the upper road side network is authenticated by another device.
Here, when the gateway 103 is newly connected to the upper road network 108, the gateway 103 is connected to the upper road network 1
FIG. 8 shows a process of authentication from other gateways 101 and 102 connected to the gateway 08. The newly connected gateway 103 broadcasts a random number request. The processing of the gateway 101 is indicated by an upper box as indicated by a broken line, and the processing of the gateway 102 is indicated by a lower box as indicated by a broken line. ing. Of course, it may be done at the same time,
It may be performed in the reverse order. When the gateway newly connects to the upper road-side network (401), the gateway 103 newly connected to the upper road-side network transmits a random number request to the upper road-side network 108 (402). Upon receiving the random number request, the gateway 101 generates a random number (403), and transmits the generated random number to the upper roadside network 108 (404). The gateway 103 newly connected to the upper road network 108 receives the random number, creates a signature for the random number using the signature private key of the gateway 103 (405), and sends the random number and the created signature to the upper road network 108. Then, the public key for signature and the public key for key distribution of the gateway 103 are transmitted (406). The reason why the random number is also transmitted is to indicate which gateway has generated the signature using the random number generated.

The gateway 101 that has transmitted the random number receives the signature, and if the random number is a random number issued by itself, verifies the received signature using the signature public key.
(407). It is assumed that a certificate is attached to the transmitted signature public key, and the gateway 101 that has received the certificate verifies the certificate. If the signature verification is successful, the key distribution public key of the gateway 103 that created the signature is registered (408). It is assumed that a certificate is attached to the transmitted key distribution public key, and that the received gateway verifies the certificate.

The gateway 102 that has received the signature for the random number created by another gateway may arbitrarily verify the signature (409). However, if the verification of the signature fails, the connection of the corresponding gateway may be prohibited. However, even if the verification of the signature for the random number created by another gateway succeeds, the corresponding gateway must not be registered. Since the random number request is broadcast to the upper road network 108, other gateways of the upper road network 108 also generate and transmit random numbers, and the same processing is executed for each gateway (410 to 416). When signing a random number, a method of preventing the replacement of the public key by including the public key as a signature target is also conceivable.

FIG. 5 is a sequence chart of a process for performing cryptographic communication via the upper roadside network. In order for the gateway to perform the transfer, the SI received by the base station from the base station connected to the local roadside network to which the gateway is connected.
D must be registered. In the example of FIG. 5, the SID (Ser
It is assumed that the device identifier has already been registered (501). The base station 106 transmitting the data
The data is encrypted with the encryption key corresponding to the SID of the data to be transmitted (502) and transmitted to the local roadside network 111 (5).
03). Each device connected to the local roadside network 111 performs normal reception processing. At the same time, the gateway 103 makes a transfer determination based on the SID of the received data (504) and transmits the data to the upper roadside network 108 (505). Note that the gateway may have a policy of transferring all transmission data without making a transfer determination.

Another gateway 10 of the upper roadside network 108
1 makes a transfer determination from the SID of the received data (5
06) If the corresponding SID matches the one registered in advance from the base station 104 of the local roadside network 109, the corresponding data is transmitted to the local roadside network 109 side. Base station 10 connected to local roadside network 109
No. 4 makes a reception determination using the SID and converts the received data into an SI.
Decryption is performed with the encryption key corresponding to D (508). In this embodiment, the local roadside networks 109 and 111 and the upper roadside network 108
Are assumed to share the same SID and encryption key, the gateways 101 and 103 can directly transfer data received from one roadside network to the other roadside network. Local roadside networks 109 and 111 and upper roadside network 10
8 uses a different SID or encryption key, or both, the gateway 101, 103
The transfer becomes possible by rewriting the ID or re-encrypting the ID.

FIG. 6 is a sequence chart of a process for issuing an encryption key in the local roadside network. FIG. 6 shows an example of a procedure when the base station 106 requests an encryption key corresponding to the SID. The upper frame (608) shows the procedure for distributing the encryption key that was encrypted when the gateway 101 was used, and the lower frame (617) shows the case where there is no encryption key corresponding to the SID in the gateways 101 and 102. 4 shows a key distribution procedure. The encryption key corresponding to the SID is a criterion for determining whether (a) the device transmits and receives with the encryption key and (b) whether data is encrypted with the encryption key. . Therefore, each base station and each gateway must have an encryption key corresponding to the SID.

According to the procedure shown in FIG.
9, 111 and the upper roadside network 108 share the same encryption key. When the base station 106 connects to the local roadside network 111 (601), the gateway 103
(602), and the public key for key distribution of the base station 106 is already registered in the gateway 103. The authentication performed in the local roadside network 111 is as follows.
This is done with a previously distributed encryption key. The base station 106 requesting the encryption key corresponding to the SID transmits a key inquiry to the local roadside network 111 by designating the SID (6.
03). Gateway 10 that received key inquiry
3 searches whether the encryption key corresponding to the received SID is registered (604). If there is an encryption key, the encryption key is encrypted with the key distribution public key of the corresponding base station 106 and the local roadside network 111 is encrypted. (In FIG. 6, the route is omitted).

If the corresponding encryption key is not registered, the gateway 103 sends a key inquiry to the upper road side network 108 (605). Upon receiving the key inquiry, the gateways 101 and 102 of the upper roadside network
Search whether the encryption key corresponding to is registered
(606,607). The corresponding encryption key is the upper roadside network 108
The processing when registered in the above gateway 101
(608). The gateway 101 having the encryption key corresponding to the SID sends the encryption key to the gateway 103 that has issued the request.
(609) with the public key for key distribution of the upper roadside network 10
Then, the SID and the encryption key are transmitted to 8 (610). At this time, the gateway 101 that transmits the encryption key creates a signature using its own secret key and transmits it together, thereby preventing transmission of an unauthorized key. The gateway 103 that has made the inquiry about the encryption key receives the response, decrypts the encryption key using its own key distribution secret key (611), and registers it (612).

At this time, if a method of adding a signature to the encryption key is adopted, the signature is verified, and the encryption key is registered only when the signature is valid. And gateway 1
03 encrypts the encryption key using the public key for key distribution of the base station 106 that has queried the key (613), and transmits the SID and the encryption key to the local roadside network 111 (614). At this time, by generating and adding a signature in the same manner, it is possible to prevent transmission of an unauthorized key. The base station 106 that has made the inquiry about the encryption key receives the data, decrypts the encryption key using its own key distribution secret key (615), and registers it.
(616).

The processing when the encryption key corresponding to the SID does not exist is shown in (617). When all gateways 101 and 102 of the upper roadside network 108 return a response indicating that there is no corresponding key (618, 619), or
If there is no response within the specified time, the gateway 103 that has requested the encryption key generates a new encryption key (620) and registers the key with itself (621). The gateway 103 encrypts the encryption key using the key distribution public key of the base station 106 that inquired about the encryption key (622), and transmits the SID and the encryption key to the local roadside network 111 (623). At this time, a method in which the gateway creates and adds a signature may be considered. The base station 106 that inquired about the encryption key receives the data, decrypts the encryption key using its own key distribution secret key (624), and registers it (625). At this time, if the signature is added, the signature is verified, and the encryption key is registered only when the signature is valid.

FIG. 7 is a sequence chart showing a procedure in which a device other than the device that has issued the encryption key updates the encryption key. In the present embodiment, the gateway 103 that has issued the encryption key performs update processing separately for each encryption key. The gateway 103 executes a key update process at regular time intervals or when a designated condition is satisfied. First, the gateway 103 generates a new encryption key (701), and encrypts the generated encryption key using the encryption key before updating (701).
2), transmits an encryption key update request to the upper road side network 108
(703). The gateways 101 and 102 connected to the upper road side network 108 receive the encryption key update request, and the gateway 1 that does not have the encryption key corresponding to the designated SID.
02 does not update (704).

The gateway 101 having the encryption key corresponding to the designated SID decrypts the received encryption key with the encryption key before update (705), and updates the encryption key with the decrypted key (7).
06). The gateway 101 encrypts the new encryption key with the encryption key before the update (707), and
Sends a request to update the encryption key. Local roadside network 109
Receives an encryption key update request, and if the base station 104 has an encryption key corresponding to the specified SID,
The encryption key is decrypted (709), and the key is updated (710). The gateway 103 that has requested the update of the encryption key issues a key update request to the local roadside network 111 to which the gateway 103 connects.

The gateway 103 encrypts the encryption key to be updated using the encryption key before the update (711), and transmits a request for updating the encryption key to the local roadside network 111 (712). Base stations 105 and 10 connected to local roadside network 111
6 receives the encryption key update request, and the base station 105 having no encryption key corresponding to the specified SID does not update the key.
(713) The base station 106 having the encryption key corresponding to the designated SID decrypts the received encryption key using the encryption key before update (714) and updates the encryption key (715). In this embodiment, for the sake of simplicity, a method in which the key is updated once is described. However, a method in which the key is updated in steps in the same manner as in the previous proposal can also be applied to the present invention. .

FIG. 8 is a sequence chart showing a key updating procedure in the case where the device that generated the key is disconnected. The gateway that has generated the encryption key is the upper roadside network 108
If the key is not updated by the gateway that generated the key, such as when disconnected from the gateway, the gateway that has the relevant encryption key other than the gateway that issued the relevant encryption key measures the update interval using a timer, etc. If the key update is not performed after a predetermined time period longer than the normal update interval, one gateway is selected from the remaining gateways (801). As a selection method, there are a method of determining priorities in advance and a method of setting randomly by random numbers or the like. The selected gateway 101 updates the encryption key in the same procedure as a normal key update.

That is, the selected gateway 101
Creates a key (802), encrypts it using this key (803), and sends a key update request to the upper roadside network 108 (804). The gateway 102 does not use the key corresponding to the SID and does not update it (805). In response to the key update request, the gateway 103 decrypts the received encryption key with the encryption key before update (806), and updates the key (8).
07). The gateways 101 and 103 encrypt using the updated key and make a key update request to the base station 104 or 105 or 106 in the lower roadside networks 109 and 111 (814, 809). The base stations 104 and 106 that have registered the key corresponding to the SID decrypt the received encryption key with the key before updating (815, 811) and update the key (81).
6,812). Also, the base station 105 does not update the key corresponding to the SID because it has not registered the key (810). In this case, the procedure is the same as the procedure in FIG. 7 except that the update source gateway is different.

[0037]

As described above, according to the present invention,
Since the same encryption key can be shared among a plurality of autonomous distributed networks connected to a higher-level autonomous distributed network, cryptographic communication and key management in a system configured by connecting a plurality of autonomous distributed networks can be realized. Security can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an autonomous decentralized system showing one embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a gateway device in FIG. 1;

FIG. 3 is a sequence chart of a process in which a device connected to an upper road-side network authenticates another device in the present invention.

FIG. 4 is a sequence chart of a process in which a device connected to an upper road-side network is authenticated by another device in the present invention.

FIG. 5 is a sequence chart of a process when a device connected to another local roadside network receives data transmitted by a device connected to the local roadside network in the present invention.

FIG. 6 is a sequence chart of a process for issuing an encryption key in the local roadside network of the present invention.

FIG. 7 is a sequence chart of a process for updating an issued encryption key in the present invention.

FIG. 8 is a sequence chart of a process in which a device other than the device that has issued the encryption key updates the encryption key in the present invention.

[Explanation of symbols]

101, 102, 103 ... gateway, 104, 10
5, 106: base station, 107: local server, 108
... Upper roadside network, 109, 110, 111... Local roadside network, 201. CPU, 202... Input device, 203... Output device, 204.
... Encryption processing unit, 208 ... Key issue processing unit, 209 ... Key update processing unit, 210 ... Key search processing unit, 211 ... Encryption key table, 212 ... Key transmission key table, 213 ... Key distribution key table, 304 , 308... Signature creation, 305, 30
9: signature, signature key, key distribution key transmission, 306, 310: signature verification, 307, 311: key distribution key registration, 401: new connection, 402: random number request, 403, 410: random number generation,
404, 411: random number transmission, 407, 715: signature verification, 406, 413: random number, signature, signature key, key distribution key transmission, 407, 415, 414: signature verification, 408, 4
16: key distribution key registration, 502: encryption, 503, 505
... Sending, 504, 506 ... Transfer judgment, 508 ... Decoding, 6
01: new connection, 602: authentication at connection, 603, 60
5 ... key inquiry, 604,606 ... key search, 60
9, 622: encryption, 610: response (SID, encryption key), 618, 619: SID, no key, 620: key generation, 611: decryption, 612, 621: key registration, 623
... SID, encryption key, 615,624 ... decryption, 616,6
15: key registration, 701: key creation, 702, 711: encryption, 703: key update (SID, encryption key), 705, 70
7, 714: decryption, 706, 710, 715: key update, 704, 713: no update, 801: key generation device determination, 802: key creation, 803, 808, 813 ... encryption, 815, 811 ... Decryption, 806,812 ... Key update, 804,814,819 ... Key update request.

Claims (5)

[Claims] 1. A method for managing an encryption key of a network that performs communication by broadcast, wherein a device connected to the network transmits a random number to another device, and another device connected to the network transmits the random number to the other device. After the signature is created, the key for encryption communication is attached and transmitted, and the device that has transmitted the random number verifies the signature received from each device to confirm the validity, and then performs the encryption communication. A method for managing an encryption key in an autonomous decentralized network, wherein a device connected to the network acquires a key for encryption communication of another device connected to the network by registering the key for the encryption. 2. In a network that performs communication by broadcast, a device connected to the network requests a random number from another device, each of the devices receiving the request for the random number transmits a random number, and The requesting device creates a signature for each of the random numbers, attaches the key for cryptographic communication and the original random number, and transmits it. The device that transmitted the random number receives the signature received from the device that requested the random number. After verifying the validity of the device and verifying its validity, by registering the key for encrypted communication, it is possible to ensure that another device connected to the network obtains the key for encrypted communication of the device connected to the network. Characteristic encryption key management method in an autonomous distributed network. 3. A network device in which a local autonomous decentralized network connecting one or more base stations is connected to an upper autonomous decentralized network via a gateway. When sharing keys for distribution among the autonomous distributed networks and issuing encryption keys in the local autonomous distributed network,
A query is made in advance as to whether there is an encryption key corresponding to another autonomous distributed network. If the encryption key exists, the encryption key is issued. If the encryption key does not exist, the encryption key is issued by itself. A key management device that generates and issues a key and periodically updates a key; and receives and distributes an encryption key or an update key from the key management device, registers and distributes the key through one or more local autonomous distributed networks. A base station that performs wireless communication with a mobile vehicle in its own network by performing cryptographic communication, and a local server that centrally manages communication in the local autonomous decentralized network. Network device to do. 4. An encryption key management method for a network in which a plurality of autonomous distributed networks are interconnected, wherein a device connected to two autonomous distributed networks is configured to transmit data transmitted by a first autonomous distributed network. To the second autonomous decentralized network,
At the time of transfer, the data is decrypted with the encryption key of the autonomous distributed network on the data transmission side, and the data is encrypted with the encryption key of the autonomous distributed network of the data transmission destination. Meanwhile, the same encryption key is shared by multiple autonomous distributed networks. By doing so, when the device connected to the two autonomous distributed networks transfers the data transmitted on the first autonomous distributed network to the second autonomous distributed network, the above processing is unnecessary. A communication method for performing cryptographic communication between multiple autonomous distributed networks. 5. A cryptographic key management method for a system in which a plurality of autonomous distributed networks are connected by a single autonomous distributed network. The devices connected to both of the autonomous distributed networks connecting the distributed networks correspond to the autonomous distributed networks other than the corresponding autonomous distributed network with respect to the autonomous distributed network connecting the autonomous distributed networks. An inquiry is made as to whether or not an encryption key already exists. If there is a corresponding encryption key, the encryption key is set as an encryption key of the corresponding autonomous distributed network. A device connected to both the autonomous distributed network and the autonomous distributed network connecting the autonomous distributed networks generates an encryption key, and the device that generated the encryption key periodically executes a key update process. , The autonomous decentralized network to which the A key update request is sent to the autonomous distributed network connecting the distributed networks, and if the key is not updated within the specified period, one device is used between the devices that did not generate the key. , And the selected device executes a key update process, in the autonomous distributed network.