JP2007067968A - Key management system, key management server and key management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manage a secret key with a time limit capable of strictly observing the time limit. <P>SOLUTION: The key management system is provided with a client terminal and a server terminal. The client terminal is provided with a means which transmits the identification information of a random key for decrypting an encrypted secret key, a means which receives the random key, and a means which decrypts the secret key by the received random key. The server terminal is provided with a means for receiving the identification information of the random key from the client terminal; a means for storing a database wherein the identification information, the random key, and time limit information are related to each other; a means for determining whether or not the identification information is valid on the basis of the time limit information related to the identification information from the database; and a means for transmitting the random key related to the identification information. By such constitution, the management of the secret key capable of strictly observing the time limit is made possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a key management system, a key management server, and a key management method, and more particularly, to a key management system, a key management server, and a key management method for setting a key expiration date.

  In order to prevent data leakage in data transmission / reception on the Internet, a method of encrypting and transmitting / receiving data has been widely used. Generally, when encrypting data, encryption is performed using key data called a public key, and when decrypting encrypted data, decryption is performed using key data called a secret key. Done.

  Since the secret key is required when decrypting the encrypted data, careful management is required for managing the secret key. What is needed here is a secret key management method. In particular, it is difficult to manage a secret key when it is desired to permit decryption only for a limited period.

As a method for permitting decryption only for a limited period, a method has been proposed in which a time limit is set for data of a secret key, and the secret key is invalidated and deleted when the time limit has passed (for example, Patent Document 1). .
JP 2005-25438 A

  However, the method disclosed in Patent Document 1 is a method of setting a time limit on the secret key itself, and has a high risk that the time limit is falsified by analyzing the data of the secret key itself.

  The present invention has been made to solve such a problem, and an object of the present invention is to manage a secret key that can strictly observe the deadline.

  The key management system according to the present invention is a key management system including a client terminal and a server terminal, and the client terminal identifies identification information of a random key for decrypting a secret key encrypted with respect to the server terminal. , Means for receiving the random key from the server, and means for decrypting the secret key using the received random key, wherein the server terminal receives the random key from the client terminal. Receiving the identification information, means for storing a database in which the identification information, the random key, and the expiration information are associated with each other, and the identification information based on the expiration information associated with the identification information from the database. Means for determining whether or not the information is valid, and the client terminal based on a result of the determination A key management system having means for transmitting said random key associated with the identification information for. With such a configuration, it is possible to manage a secret key that can strictly observe the deadline.

  The means for determining whether or not the identification information is valid may be characterized by acquiring time information from a dedicated time server or the like and comparing the acquired time information with time limit information. This makes it possible to prevent unauthorized operation of time information.

  The secret key may be encrypted using a common encryption method.

  The key management server according to the present invention is a key management server for managing a secret key, the means for receiving identification information of a random key from a client terminal, and the identification information, the random key, and expiration date information associated with each other Means for storing a database; means for determining whether or not the identification information is valid based on the time limit information associated with the identification information from the database; and the client terminal based on the result of the determination Is a key management server having means for transmitting the random key associated with the identification information. With such a configuration, it is possible to manage a secret key that can strictly observe the deadline.

  The means for determining whether or not the identification information is valid may be characterized by acquiring time information from a dedicated time server or the like and comparing the acquired time information with time limit information. This makes it possible to prevent unauthorized operation of time information.

  The secret key may be encrypted using a common encryption method.

  A key management method according to the present invention includes a client terminal and a server terminal, and executes an encryption step and a decryption step, wherein the client terminal encrypts a secret key. Generating a random key for generating, a step in which the client terminal transmits the generated random key to the server terminal, an identification information corresponding to the random key received by the server terminal, and Generating a deadline information; a step in which the server terminal stores the random key, the identification information, and the deadline information in association with each other; and the server terminal sends the identification information to the client terminal. Transmitting, and the client terminal uses the random key to secretly And the client terminal stores the encrypted secret key and the received identification information in association with each other, and the decryption step includes the client terminal and the server terminal. Transmitting the identification information to the server, the server terminal obtaining the deadline information stored in association with the identification information from the database, and the server terminal based on the deadline information. Determining whether the identification information is valid; and when the server terminal determines that the identification information is valid, the client terminal assigns the random key associated with the identification information to the client terminal. Acquiring from the database, and the server terminal acquires the acquired random key in the client And transmitting relative preparative terminal, the client terminal is a key management method comprising the step of decrypting the secret key using the random key received. In this way, it is possible to manage a secret key that can strictly observe the deadline.

  According to the present invention, it is possible to manage a private key with a time limit that can strictly observe the time limit.

Embodiment 1 of the Invention
FIG. 1 is a schematic diagram showing the overall configuration of a key management system according to the present invention. The key management system according to the present invention includes a key server 1, a PC (Personal Computer) 2, a PC 3, and a PC 4. The key server 1 and PC2, the key server 1 and PC3, and the key server 1 and PC4 are connected via a network. The network here may be connectable from various fields such as the Internet, or may be usable only within a narrow range such as an intranet. It is assumed that a dedicated key management application is built in each of PC2, PC3, and PC4, and the key management application operates as necessary. The PCs 2, 3, and 4 can be substituted for each other.

  The key server 1 is a server for managing key data, and a commercially available PC or server can be used as it is. The key server 1 is connected to the PC 2 via a network. The key server 1 can send and receive data to and from the PC 2 via the network.

  PC2, PC3, and PC4 are PCs with built-in key management applications, and commercially available PCs can be used as they are. In this case, the key management application is preinstalled as a program.

  FIG. 2 shows an example of the hardware configuration of the PC 2 in the present invention. The key server 1, PC3, and PC4 have the same configuration. The PC 2 includes a central processing unit (CPU) 201 and a memory 204. The CPU 201 and the memory 204 are connected to a hard disk device 213 as an auxiliary storage device via a bus. Storage medium drive devices such as the flexible disk device 220, the hard disk device 213, and the CD-ROM drive 226 are connected to the bus via various controllers such as the flexible disk controller 219 and the IDE controller 225. A portable storage medium such as a flexible disk is inserted into a storage medium driving device such as the flexible disk device 220.

  The storage medium can store a computer program for implementing the present embodiment by giving instructions to the CPU 201 in cooperation with the operating system. The various means in this embodiment are all computer programs. Further, data generated by the program in the present embodiment is stored in the memory 204, and is also stored in the hard disk device 213 as necessary. The computer program is executed by being loaded into the memory 204. The computer program can be compressed or divided into a plurality of pieces and stored in a storage medium. The hardware configuration typically comprises user interface hardware.

  User interface hardware includes, for example, a display device 211 such as a pointing device (mouse 207, joystick, etc.) or keyboard 206 for inputting, or a liquid crystal display for presenting visual data to the user. . The image data is stored in the VRAM 209 and sent from the VGA controller 208 to the display device 211 via the DAC / LCD controller (LCDC) 210. All input from the user in this embodiment is performed through the mouse 207, the keyboard 206, and the like. In addition, a modem can be connected via the serial port 215, and it can be connected to a network via the serial port 215 or the communication adapter 218 to communicate with other computer systems. The above configuration can be omitted as necessary.

  Next, a flow of processing at the time of secret key encryption in the key management system according to the present invention will be described using the sequence diagram shown in FIG.

  First, the PC 2 generates a random key using a built-in key management application (S11). The random key is key data for encryption generated by a random number. When the generation of the random key by the PC 2 is completed, the PC 2 transmits the random key generated by the key management application to the key server 1 (S12). Thereafter, all processing performed by the PC 2 is performed by the key management application.

  When receiving a random key from the PC 2, the key server 1 issues a key ID corresponding to the received random key (S13). The key ID may be assigned a number in order from 1, or may be assigned at random. However, it is assumed that key IDs do not overlap for different random keys.

  Further, the key server 1 assigns time limit information corresponding to the received random key (S14). The term information is information indicating the term of validity of the secret key that can decrypt the data encrypted with the received random key. Further, only the deadline information is given here, but other information such as name information for identifying the person may be given.

  The key server 1 associates the received random key, the issued key ID, and the assigned time limit information with each other and stores them in the database provided in the key server 1 (S15). When the storage in the database is completed, the key server 1 transmits a key ID corresponding to the received random key to the PC 2 (S16).

  When receiving the key ID from the key server 1 by the key management application, the PC 2 encrypts the secret key using the random key (S17). Although the encryption method here is not particularly limited, for example, a common encryption method such as Triple DES (Data Encription Standard), AES (Advanced Encryption Standard), or the like is conceivable.

  The encrypted secret key is stored in the storage means of the PC 2 with the key ID information added. In order to use this secret key, it is necessary to obtain a random key from the key server 1. Since the key server 1 manages the expiration date of the random key, it is possible to limit the use of the secret key by the expiration date. It becomes.

  A specific example will be described. FIG. 6 is a diagram specifically showing the flow of data between the key server 1 and the PC 2 in the present invention.

  Private key data is generated and stored in the PC 2 in advance. The secret key data here is “as37638888”. First, the PC 2 generates a random key. The random key generated here is “FA01”. Here, the length of the key data of the random key is not necessarily four digits. Further, the random key may be expressed by a number instead of a character string.

  When the generation of the random key by the PC 2 is completed, the PC 2 transmits “FA01” that is the generated random key to the key server 1. When the key server 1 receives the random key from the PC 2, the key server 1 issues a key ID corresponding to the received random key. Here, a key ID “0002” is assigned.

  Moreover, the key server 1 gives the time limit information corresponding to the received random key. The term information here is “2005-07-08”, that is, until July 8, 2005. The key server 1 associates the received random key, the issued key ID, and the assigned time limit information with each other and stores them in a database provided in the key server 1. The new record in FIG. 6 shows an image of the database.

  When the storage in the database is completed, the key server 1 transmits a key ID corresponding to the received random key to the PC 2. Here, the key ID “0002” assigned earlier is transmitted to the PC 2. When the PC 2 receives the key ID from the key server 1 by the key management application, the PC 2 encrypts the secret key using the random key. As shown in FIG. 6, the private key data “as37638888” is encrypted using the random key “FA01”, and the encrypted private key data “sk38ausea6838a7sa87” is generated.

  The encrypted secret key is stored in the storage means of the PC 2 with the key ID information added. That is, the secret key data “sk38auusea6838a7sa87” and the received key ID “0002” are stored in association with each other.

  Next, the flow of processing when an encrypted secret key is used will be described using the sequence diagram shown in FIG.

  First, the PC 2 transmits a key ID corresponding to the encrypted secret key to the key server 1 (S21). When the key server 1 receives the key ID from the PC 2, the key server 1 acquires time limit information corresponding to the received key ID (S22), and determines whether or not the time limit has passed (S23).

  When the key server 1 has a built-in clock, it is possible to use a built-in clock, or obtain time information from a dedicated time server or the like. You may make it determine by comparing time information and time limit information. However, the method of receiving the time information from the PC 2 is not preferable because the secret key can be obtained illegally even if the time limit expires due to the falsified time information.

  If it is determined that the time limit has not passed, error processing is performed (S24). The method of error processing is not particularly limited, but a method of transmitting an error signal from the key server 1 to the PC 2 is conceivable. If it is determined that the time limit has not passed, the key server 1 acquires a random key corresponding to the received key ID from the database provided in the key server 1 (S25). When the acquisition of the random key is completed, the key server 1 transmits the acquired random key to the PC 2 (S26).

  When the PC 2 receives the random key from the key server 1, it decrypts the encrypted secret key using the received random key (S27). In this way, the PC 2 can obtain the secret key only when it is within the time limit.

  A specific example will be described. FIG. 7 is a diagram specifically illustrating a data flow between the key server 1 and the PC 2 at the time of secret key decryption in the present invention.

  The PC 2 stores the encrypted secret key data “sk38auusea 6838a7sa87” and the key ID “0002” corresponding to the random key for decrypting the secret key data. First, the PC 2 transmits a key ID “0002” to the key server 1.

  When the key server 1 receives the key ID “0002” from the PC 2, the key server 1 acquires time limit information corresponding to the received key ID. As shown in FIG. 7, the term information corresponding to the key ID “0002” is “2005-07-08”. The key server 1 determines whether or not the key ID is valid from the time at the time of comparison and the time limit information.

  As a result of the determination, if the key ID is valid, the key server 1 acquires the random key “FA01” corresponding to the key ID “0002”. Thereafter, the key server 1 transmits a random key “FA01” to the PC 2.

  When the PC 2 receives the random key “FA01” from the key server 1, the PC 2 decrypts the secret key data “sk38ausea6838a7sa87” encrypted using the received random key “FA01”.

  When the decryption is completed, the PC 2 can acquire the secret key data “as 3763888818”. In this way, the time limit is managed by the key server 1, and the PC 2 can obtain the secret key data only during the period based on the time limit information.

  Next, the flow of processing when the secret key is moved from the PC 2 to the PC 3 will be described using the sequence diagram shown in FIG.

  First, the PC 2 decrypts the secret key using the key management application (S31). The procedure for decrypting the secret key is the same as described above, and a description thereof is omitted here.

  When the decryption is completed and the private key is acquired, the PC 2 encrypts the private key again (S32). The procedure for encrypting the secret key is the same as described above, and the description thereof is omitted here.

  When the encryption of the private key is completed, the PC 2 associates the key ID acquired when newly encrypted with the encrypted private key data and transmits it to the PC 3 (S33). The PC 3 can acquire the secret key using the received key ID and the encrypted secret key data. In addition, the private key data stored in the PC 2 is not transmitted to the PC 3 as it is, but is decrypted and encrypted, and the private key data including another key ID is transmitted to the PC 3 so that the time limit is separately set. It becomes possible to set to.

  A specific example will be described. FIG. 8 is a diagram specifically showing the flow of data between the key server 1 and the PC 2 at the time of secret key duplication in the present invention.

  The PC 2 stores the encrypted secret key data “sk38auusea 6838a7sa87” and the key ID “0002” corresponding to the random key for decrypting the secret key data. First, the PC 2 decrypts the secret key using the key management application, and acquires the secret key data “as37638888”.

  After that, the PC 2 encrypts the secret key data “as37638888”. At this time, the PC 2 generates a new random key different from the existing random key “FA01”, and transmits it to the key server 1. The random key generated here is “386A”.

  As illustrated in FIG. 8, the key server 1 stores a new random key “386A”, a key ID “0003” corresponding to the random key “386A”, and time limit information “2005-07-08”. The deadline information can be changed as necessary.

  The secret key data encrypted with the new random key “386A” is “ea3115a7saa33ggg87”. The PC 2 associates this newly encrypted secret key data “ea3115a7saa33gggg87” with the corresponding key ID “0003” and transmits it to other PCs such as PC3 and PC4. In this way, the secret key is duplicated.

It is a schematic diagram which shows the whole structure of the key management system in this invention. It is a block diagram which shows the structure of the key server and PC in this invention. It is a flowchart which shows the flow of a process of the key management system in this invention. It is a flowchart which shows the flow of a process of the key management system in this invention. It is a flowchart which shows the flow of a process of the key management system in this invention. It is a figure which shows the specific example of the flow of a process of the key management system in this invention. It is a figure which shows the specific example of the flow of a process of the key management system in this invention. It is a figure which shows the specific example of the flow of a process of the key management system in this invention.

Explanation of symbols

1 Key server 2 PC
3 PC
4 PC
201 CPU
204 Memory 206 Keyboard 207 Mouse 208 VGA controller 211 Display device 213 Hard disk device 215 Serial port 218 Communication adapter 219 Flexible disk controller 220 Flexible disk device 225 IDE controller 226 CD-ROM drive

Claims (7)

A key management system comprising a client terminal and a server terminal,
The client terminal transmits a random key identification information for decrypting an encrypted secret key to the server terminal, a means for receiving the random key from the server, and the received random key. Using means for decrypting the secret key,
The server terminal includes means for receiving identification information of the random key from the client terminal, means for storing a database in which the identification information, the random key, and time limit information are associated with each other, and the identification information from the database. Means for determining whether or not the identification information is valid based on the associated deadline information; and the random key associated with the identification information for the client terminal based on the determination result. A key management system having means for transmitting.   The means for determining whether or not the identification information is valid is obtained by acquiring time information from a dedicated time server and comparing the acquired time information with time limit information. Key management system.   3. The key management system according to claim 1, wherein the secret key is encrypted using a common encryption method. A key management server for managing private keys,
Means for receiving identification information of a random key from a client terminal;
Means for storing a database in which the identification information, the random key, and the deadline information are associated with each other;
Means for determining whether the identification information is valid based on the time limit information associated with the identification information from the database;
A key management server comprising means for transmitting the random key associated with the identification information to the client terminal based on the determination result.   5. The means for determining whether or not the identification information is valid is obtained by acquiring time information from a dedicated time server and comparing the acquired time information with time limit information. Key management server.   The key management server according to claim 4 or 5, wherein the secret key is encrypted using a common encryption method. A key management method comprising a client terminal and a server terminal and executing an encryption step and a decryption step,
The encryption step includes
The client terminal generates a random key for encrypting a secret key;
The client terminal transmitting the generated random key to the server terminal;
The server terminal generating identification information and time limit information corresponding to the received random key;
The server terminal stores the random key, the identification information, and the time limit information in a database in association with each other;
The server terminal transmitting the identification information to the client terminal;
The client terminal encrypting a secret key using the random key;
The client terminal has a step of storing the encrypted secret key and the received identification information in association with each other;
The decoding step includes
The client terminal transmitting the identification information to the server terminal;
The server terminal obtaining the time limit information stored in association with the identification information from the database;
The server terminal determining whether the identification information is valid based on the time limit information;
When the server terminal determines that the identification information is valid, the client terminal obtains the random key associated with the identification information from the database;
The server terminal transmitting the acquired random key to the client terminal;
A key management method comprising a step in which the client terminal decrypts a secret key using the received random key.

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