JP2003179596A - Client/server system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a client/server system in which safe cryptographic communication can be performed without decelerating a processing speed of the cryptographic communication. <P>SOLUTION: In the client/server system for performing the prescribed cryptographic communication between a server and a client by using a prescribed common key, the server and the client are each provided with two prescribed common keys of different generations and a key storage means for storing the next distribution key for deciphering the prescribed common key of the generation next to these two prescribed common keys, and a communication control means is provided for performing the prescribed cryptographic communication between the server and the client by using the prescribed common key of the latest generation between two prescribed common keys respectively stored in these key storage means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a client / server system, and more particularly to a system for performing encrypted communication between a server and a client using a predetermined common key.

[0002]

2. Description of the Related Art Conventionally, in a client / server system, a DES (Date Enc
When encrypted communication is performed using the ryption Standard) method, the server and the client use a common key. That is, the sender of the information encrypts the predetermined information with the common key and sends it out, and the receiver of the information decrypts the received encrypted information with the common key to extract the predetermined information. ing.

In order to perform secure encrypted communication by the above-mentioned DES method, it is necessary to securely distribute the common key from the server to the client in advance. As a method of distributing this common key, there is a method of encrypting and distributing the common key using a public key cryptosystem widely known as RSA. That is, the server encrypts the common key using the public key, and the client decrypts the received encrypted information using the secret key to extract the common key and obtain the common key.

[0004]

However, in the case of distributing the common key using the public key of RSA in the encrypted communication in the above-mentioned conventional client-server system, the RS and RS are distributed to all devices of the server and each client respectively.
A module for executing the public key cryptosystem of A has to be incorporated, which has a drawback that the equipment cost becomes high.

In addition, the module for executing the RSA public key cryptosystem has a drawback that the encryption processing speed is slow, and therefore the processing speed of the encrypted communication of the entire system is reduced. Further, when the RSA public key cryptosystem is adopted, there is a management problem that the key management of the public key and the private key must be thoroughly performed.

Therefore, the present invention has been made in order to solve the above-mentioned drawbacks, and its purpose is to enable a secure distribution of a common key with a simple structure, and to encrypt the entire system. It is to provide a client-server system that does not reduce the communication processing speed.

[0007]

In order to achieve the above-mentioned object, a client-server system according to the present invention is a client-server system according to claim 1, wherein a predetermined common key is used between a server and a client. For decrypting two predetermined common keys of different generations and a predetermined common key of the next generation of those two predetermined common keys in the client-server system for performing the encrypted communication of Key storage means for storing the next distribution key of the server is provided, and the predetermined common key of the latest generation of the two predetermined common keys respectively stored in the key storage means is used for the server and It is characterized in that a communication control means for performing a predetermined encrypted communication between the clients is provided. The client-server system according to claim 2, when a predetermined common key of a new generation is adopted, sends the newly adopted predetermined common key and next distribution key from the server to the client, The client is provided with a new common key extracting means for decrypting the newly adopted predetermined common key by using the next distribution key stored in advance and extracting the newly adopted predetermined common key. It is characterized by that. In the client-server system according to the third aspect, when a matching state of a predetermined next distribution key stored in each of the server and the client cannot be obtained, the client stores the client in the server. Encrypt arbitrary data with a specified next distribution key and send it to that server, and that server uses the next distribution key of multiple generations managed by that server for the data sent encrypted from that client. Decrypt and determine the generation successfully decrypted as the generation that the client has, encrypt the given common key and the next distribution key that the server is currently using with the next distribution key that the client has, and send to the client It is characterized in that a common key sending means is provided. The client-server system according to a fourth aspect is characterized in that the device existing between the server and the client does not have the information of the next key distribution. In the client server system according to claim 5, the device existing between the server and the client receives all the key information of the device on condition that the device located lower than the device receives the predetermined key information. It is characterized in that a deleting means for deleting is provided. According to a sixth aspect of the client-server system, the server has key information of all generations. According to a seventh aspect of the client server system of the present invention, the first predetermined common key and the next key distribution to the client are set off-line. According to another aspect of the client server system of the present invention, the server is a host computer that manages station service equipment such as an automatic ticket gate, and the client is station service equipment such as the automatic ticket gate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a client server system according to an embodiment. Server 1
Is a station service device such as an automatic ticket gate or an automatic ticket vending machine installed at each station, or a station service device control device that manages and controls each station service device at each station. Station control equipment control device is also included.) It is shown as a host computer installed in a predetermined center such as the head office of a railway company that comprehensively manages. And
The client 10 is shown as station service equipment installed in a station. Regarding the number of servers and clients, a plurality of clients corresponding to a plurality of stations are actually connected to one server, but here, for ease of explanation, one server and one client are connected. Shown as a client.

The server 1 has a communication control unit 2 including a well-known communication device for communicating with the client 10 side, and a predetermined process such as a totaling process of ticket sales and a totaling process of the number of passengers of an automatic ticket gate. An arithmetic unit 3 for performing arithmetic processing for the above processing and a processing unit 4 for performing predetermined processing such as printing out the calculation result and inputting predetermined information are provided.

The arithmetic unit 3 has a CPU 3b for performing a predetermined arithmetic processing based on the system program data stored in the memory 3a and the predetermined data obtained from the client 10 side. Further, in the memory 3a,
A plurality (three in the illustrated example) of key groups a, b, and c for performing encrypted communication between the server 1 and the client 10 are stored (stored), and the key groups a, b, and c are stored. Two common keys and one subsequent distribution key are stored therein. The key groups a, b, and c will be described later. Further, these key groups a, b, and c can be stored in a memory (not shown) in the communication control unit 2.

The client 10 includes a communication control unit 11 including a well-known communication device for communicating with the server 1 side.
There are various processing units such as a calculation unit 12 that performs a predetermined calculation process for station service equipment and a door drive unit that drives a door when the station service device is an automatic ticket gate. In this case, the processing unit 13 is various processing units such as a ticket issuing processing unit that issues a ticket, and when the station service device is a station service device control device, various processing units such as an input / output processing unit. have.

The arithmetic unit 12 carries out a predetermined arithmetic processing based on the system program data stored in the memory 12a and the predetermined data obtained from the server 1 side.
It has U12b. Further, in the memory 12a,
One key group for performing encrypted communication between the server 1 and the client 10 is stored. In FIG. 1, the key group b among the key groups a, b, and c stored in the server 1 is stored (stored). The key group B can be stored in a memory (not shown) in the communication control unit 11.

Key groups a, b, respectively stored in the memory 3 of the server 1 and the memory 12a of the client 10
The common keys K1 to K4 and the next distribution keys K3 'to K5' in c are
The key length is a predetermined number of bits. The subscripts "1 to 4, 3'to 5 '" of the codes of these keys represent the generation of the key, and it is determined that the cipher strength becomes stronger as the generation becomes newer. Therefore, for example, the common key K2 is newer in generation than the common key K1, and the encryption strength is strong.
Also, the version of the key is designed so that the common key K3 is newer in generation than the common key K2 and the encryption strength is stronger.

Of the key groups a, b, and c, the key group a is for testing and will be described later. The key groups (b) and (c) are used when performing a predetermined encrypted communication between the server 1 and the client 10. In the example of FIG. 1, the key group (b) is selected and the common key K3 therein is used to determine a predetermined value. Indicates that encrypted communication is being performed.

The key group C is used when the next-generation common key K4 of the above-mentioned common key K3 is adopted for encrypted communication between the server 1 and the client 10. This key group C can be prepared in the memory 3a of the server 1 in advance,
Alternatively, it may be stored prior to the use of the common key K4. As is clear from the above, in the memory 3a of the server 1, key groups (K4, K5, K6 ') of different generations (K5, K6, K
7 '), (K6, K7, K8') ... Are stored in advance or each time a new common key is adopted.

Next distribution key K3 'in each of the key groups a, b, and c
K5 'is used when the common key sent from the server 1 to the client 10 is decrypted by the client 10 and the common key sent from the server 1 is extracted. The operation of the next distribution keys K3 'to K5' will be described later.

In the client-server system shown in FIG. 1, a predetermined common key K3 stored in the key group B of the memory 3a of the server 1 and a predetermined common key K3 stored in the key group B of the memory 12a of the client 10. Predetermined encrypted communication is performed between the server 1 and the client 10 using the common key K3. That is, the server 1 and the client 10
Since the encrypted communication between them is performed using one common key K3, a high communication speed can be secured, and therefore,
For example, it is possible to sufficiently deal with a case where a predetermined processing speed is required such as encrypted communication between a host computer of a railway company and station equipment provided at each station.

Next, the distribution of the common key will be described with reference to FIGS. FIG. 2 shows a set of common keys and a method of using the common key when the client 10 is manufactured by the manufacturer.

Now, assuming that a client 10 corresponding to a station service device such as an automatic ticket gate is manufactured by a maker and has reached a communication test stage, the memory 1 of the client 10 is tested.
A key group a stored in the memory 3a of the server 1 for testing is set in 2a offline. That is, it is set manually without depending on the encrypted communication from the server 1. In this key group a, two common keys K1 and K
Since 2 and one next distribution key K3 'are included, the client 10 can perform the test encrypted communication with the server 1 using either the common key K1 or K2. After this test, the client 10
Is installed in a predetermined place (a predetermined station when the client 10 is a station service device).

FIG. 3 shows a common key distribution method when the client 10 is installed in a predetermined place and starts operation. Client 10 installed in a predetermined place
Stores a test key group a used in the communication test. Then, from the server 1, a predetermined key group B including a common key K3 that is more advanced than the most common key K2 that is the most advanced of the common keys K1 and K2 used for testing is encrypted. It is sent to the client in the form (see FIG. 3A).

When the client 10 receives the key group B from the server 1, the client 10 decrypts the common key K3 by using the next distribution key K3 'stored in advance by the client 10, and the client 10 stores it in advance. Common key K2 and the next-generation common key K sent from the server 1
The next key distribution K4 'for decrypting 4 forms the same key group b as the key group b possessed by the server 1 and stores it. Therefore, between the server 1 and the client 10, the common key K3 whose generation is more advanced than the common key K2 used for the test is stored (see FIG. 3B).

As described above, since the common key K3 is stored in the server 1 and the client 10, respectively,
After that, encrypted communication using this common key K3 becomes possible (see FIG. 3 (c)).

By the way, it is assumed that the common key K3 used for the encrypted communication has to be changed for some reason. Of course, it is desirable that the change of the common key is changed regularly or irregularly in order to secure the security more.

A common key K4 that is more advanced than the common key K3
When adopting, the key group (K3, K4, K5 ') (see FIG. 1) including the common key K4 is first set in the server 1. That is, the key group C including the common key K4 that has been upgraded from the common key K3 up to that point is set.
The key group C may be set in the server 1 in advance. Then, when the key group C is set in the server 1, the key group C is sent from the server 1 to the client 10 by a predetermined encrypted communication. The client 10
When the key group C is received from the server 1, the client 10 decrypts it by using the next distribution key K4 'stored in advance and extracts the common key K4. Therefore, since the server 1 and the client 10 have the common key K4, respectively, the encrypted communication using the common key K4 becomes possible thereafter.

FIG. 4 shows a common key distribution method when the key group coincidence state cannot be obtained between the server 1 and the client 10, that is, when the key groups cannot be synchronized at all. . Such synchronization deviation occurs when the server 1 performs cryptographic communication with a client (not shown) while the client 10 is idle, and when the common key is updated in the cryptographic communication. Figure 4
In (a), the key group D is currently in use on the server 1,
On the other hand, the client 10 stores the key group B two generations ago, which indicates that the two are not synchronized.

As described above, when the key groups are not synchronized with each other, first, the key group B stored in the client 10 from the client 10 to the server 1 is used as arbitrary data, and this is a predetermined encryption. It is sent to the server 1 by communication (see FIG. 4B). When the server 1 receives the information from the client 10, the server 1 tries the decryption in order from the newest key group (key group C in FIG. 4) to the oldest one, and the client group possesses the successfully decrypted key group. Existing key group (key group B in FIG. 4). The server 1 determines that the request from the client 10 is valid when the key group possessed by the client 10 matches the key group possessed by the server 1 (see FIG. 4B).

When the server 1 determines that the key group possessed by the client 10 is the key group B, the server 1 instructs the client 10 to use the key group of the next generation of the key group B currently in use. Up to the key groups, that is, the key groups C and D are transmitted by predetermined cryptographic communication. Therefore, the key group D currently used by the server 1 is finally stored in the client 10 (see FIG. 4C).
As a result, both the server 1 and the client 10 have the common key K5, and thereafter, encrypted communication using this common key K5 becomes possible (see FIG. 4 (d)).

When the client 10 is a station service device such as an automatic ticket gate, another device such as a station service device control device exists in the communication path between the server 1 and the client 10. In this way, when another device exists between the server 1 and the client 10, the key information from the server 1 is transmitted to the client 10 and stored in the device located in the middle of the conditions. All key information is deleted,
Safety is secured. That is, in distributing the key information, the device on the way does not have the next key distribution, and the key information distributed on the device on the way is distributed when the ACK is received from all the lower-level devices. The key information is padded with "0" or the like, and any trace of the key is deleted.

[0029]

According to the client server system of the first aspect of the present invention, the server and the client have two predetermined common keys of different generations and a predetermined common of the next generation of the two predetermined common keys. A key storage means for storing the next distribution key for decrypting the key is provided, and a predetermined common key of the latest generation of the two predetermined common keys stored in the key storage means. Since the communication control means for performing the predetermined encrypted communication between the server and the client is provided by using, the highly secure communication can be performed without reducing the processing speed of the encrypted communication. The client server system according to claim 2 of the present invention is
When a predetermined common key of a new generation is adopted, the server sends the newly adopted predetermined common key and the next distribution key to the client, and the client receives the newly adopted predetermined common key. Since a new common key extracting means for decrypting the common key of is decrypted using the next distribution key stored in advance and extracting the newly adopted predetermined common key,
The new common key can be safely distributed. According to the third aspect of the present invention, the client server system stores the client in the server when the client and the client cannot obtain the matching state of the predetermined next distribution keys stored in the server and the client, respectively. The specified next distribution key is used to encrypt arbitrary data and send it to that server. At that server, the data encrypted and sent from that client is sent to the next generation of multiple generations managed by that server. The client decrypts with the distribution key, determines that the generation successfully decrypted is the generation that the client has, and encrypts the predetermined common key and the next distribution key that the server is currently using with the next distribution key that the client has, and then the client Since the common key sending means for sending to F is provided, a new common key can be safely distributed. In the client server system according to the fourth aspect of the present invention, since the device existing between the server and the client does not have the information of the next key distribution, the security of the key can be secured. In the client-server system according to claim 5 of the present invention, the device existing between the server and the client does not require any device in the device provided that the device located lower than the device receives the predetermined key information. Since the deleting means for deleting the key information is provided, the security of the key can be ensured. In the client-server system according to claim 6 of the present invention, the server has the key information of all generations, so that the generation of the key information possessed by the client can be easily determined. The client server system according to claim 7 of the present invention is
Since the first predetermined common key and the next key distribution to the client are set off-line, the communication test can be easily performed by the client manufacturer. In the client server system according to claim 8 of the present invention, the server is a host computer that manages station service equipment such as an automatic ticket gate, and the client is a station service device such as the automatic ticket gate. Highly secure communication can be performed without reducing the processing speed of encrypted communication between station service devices.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a client server system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a common key distribution method.

FIG. 3 is an explanatory diagram for explaining a common key distribution method.

FIG. 4 is an explanatory diagram illustrating a common key distribution method.

[Explanation of symbols]

1 server 2 Communication control unit 3 operation unit 3a memory 3b CPU 4 processing units 10 clients 11 Communication control unit 12 Operation part 12a memory 12b CPU 13 Processing unit K1-K5 common key K3'-K6 'next key distribution

Claims (8)

[Claims] 1. A client-server system for performing a predetermined encrypted communication between a server and a client using a predetermined common key, wherein the server and the client have two predetermined common keys of different generations and the two common keys. Key storage means for storing the next distribution key for decrypting the predetermined common key of the next generation of the predetermined common key is respectively provided, and two predetermined common keys stored in the key storage means, respectively. A client-server system comprising communication control means for performing predetermined encrypted communication between the server and its clients using a predetermined common key of the latest generation of the keys. 2. The client-server system according to claim 1, wherein when a new generation of a predetermined common key is adopted, the server newly supplies the predetermined common key and the next key distribution to the client. , A new common key for decrypting the newly adopted predetermined common key received by the client using the pre-stored next distribution key and extracting the newly adopted predetermined common key. A client-server system comprising extraction means. 3. The client-server system according to claim 1 or 2, wherein when the predetermined next key distributions stored in the server and the client cannot be matched, the client sends the server to the server. Encrypts arbitrary data with the specified next distribution key stored in the client and sends it to the server, and the server manages the data sent from the client encrypted and sent by the server. Next generation key is used to determine the generation successfully decrypted by the client, and the predetermined common key and the next distribution key currently used by the server are used as the next distribution key of the client. A client-server system characterized by comprising a common key sending means for encrypting and sending to a client. 4. The client-server system according to claim 1, wherein the device existing between the server and the client does not have information on the next key distribution. 5. The client-server system according to any one of claims 1 to 4, wherein the device existing between the server and the client is that the device located lower than the device has received the predetermined key information. A client-server system characterized in that a deleting means for deleting all key information in the device is provided as a condition. 6. The client-server system according to claim 1, wherein the server has key information for all generations. 7. The client-server system according to claim 1, wherein the first predetermined common key and the next key distribution to the client are set off-line. 8. The client-server system according to claim 1, wherein the server is a host computer that manages station service equipment such as an automatic ticket gate,
A client / server system in which a client is a station service device such as an automatic ticket gate.