JP7107241B2 - Key sharing method, key sharing system, agent terminal - Google Patents

Description

The present invention relates to a key sharing method, a key sharing system, and an agent terminal in which a plurality of agents share an access key for accessing a database accessible with a single access key provided in a server.

In recent years, services provided by servers connected to networks such as the Internet (cloud services) have been used. In cloud services, a cloud service provider separate from the company's own organization manages the infrastructure. Therefore, if the database built on the server on the cloud is not encrypted, there is a possibility that the contents of the database can be seen by the cloud service provider.

Therefore, consider operating a database built on a server on the cloud. A terminal that accesses the database or an application running on that terminal is called an agent.

The database on the server is encrypted, and the access key for accessing the database is not held by the server on the cloud, but only by trusted agents. When a trusted agent accesses a database, it encrypts its own access key using its own secret key (or the server's public key) and sends it to the server. The server decrypts the encrypted access key using the trusted agent's public key (or its own private key), accesses the database using the decrypted access key, and sends the acquired data to the trusted agent. and delete the access key. Information leakage is prevented by concealing the decryption and deletion of this encrypted access key from the cloud service provider by the application program installed on the server.

Note that the server stores the public keys of trusted agents, and the server only accepts communications signed by the corresponding private key. Even if it is not specified, it is assumed that the signature created by the trusted agent with its private key is verified in the communication between the server and the trusted agent. A method of verifying a signature between a server and an agent (client) to perform secure communication is disclosed in Patent Document 1, for example.

In such a system, consider sharing an access key for accessing a database among multiple agents. In particular, consider sharing an access key between a trusted agent that already possesses an access key and a new entrant agent that does not possess an access key.

Conventionally, for example, a new entrant agent sends its own public key to a trusted agent, registers its own (new entrant agent) public key to the trusted agent, and the trusted agent holds the public key. asks you (the new entrant agent) to send you an access key to The trusted agent registers the new entry agent's public key with the server according to the request from the new entry agent. Also, the trusted agent encrypts the access key it holds using the public key of the new entry agent and transmits the encrypted access key to the new entry agent. The new entrant agent decrypts the received encrypted access key using its private key. By this procedure, the public key of the new entrant agent is registered in the server to enable communication between the new entrant agent and the server, and access to the database by the new entrant agent using the access key.

JP 2006-518190 A

One of the advantages of cloud services is that they can be accessed from anywhere with an internet connection. With this advantage, in the above system, it is possible to realize a configuration in which the environment in which the trusted agent is placed and the environment in which the new entrant agent is placed are different, that is, a configuration that is physically separated, such as at different offices. . In order to improve work efficiency and ensure security, it is conceivable that a dedicated person in charge shares the access key. If the above-described access key sharing work is performed by one worker, the worker must go back and forth several times between the environment where the trusted agent is placed and the environment where the new entry agent is placed. Specifically, first, the new entry agent is operated to transmit the public key to the trusted agent. Next, the trusted agent is operated to register the public key of the new entry agent in the server, encrypt the access key, and transmit the encrypted access key to the new entry agent. It then operates the new entrant agent to decrypt the encrypted access key. Thus, after working with the new entrant agent, it is necessary to move the work environment to work with the trusted agent, and then move the work environment again to work with the new entrant agent. There is a problem that this multiple times of coming and going becomes a burden on the worker.

SUMMARY OF THE INVENTION An object of the present invention is to provide a key sharing method, a key sharing system, and an agent terminal thereof that reduce the burden on workers in terms of the load caused by the workers moving back and forth between different environments multiple times. .

A key sharing method according to one aspect of the present invention is a key sharing method in which an access key for accessing a database provided in a server is shared by a plurality of agents, wherein a trusted agent having the access key uses the access key encrypts the access key with a temporary public key that is temporarily used when sharing the access key, transmits the temporary public key and the encrypted access key to the server, and exports a temporary private key corresponding to the temporary public key and the server stores the temporary public key received from the trusted agent in a first storage unit, and stores the encrypted access key received from the trusted agent in a second storage unit. , a new agent without the access key imports the temporary private key exported by the trusted agent, generates a signature using the imported temporary private key, and sends the generated signature to the server. , the server verifies the signature received from the new agent using the temporary public key stored in the first storage unit, and stores the signature in the second storage unit if the signature verification is successful. transmitting the stored encrypted access key to the new agent, and the new agent decrypts the encrypted access key received from the server with the imported temporary private key. and

After acquiring the access key, the new agent transmits to the server an agent public key used for secure communication with the server, and the server transmits the temporary public key stored in the first storage unit. may be replaced with the agent public key.

The server may delete the encrypted access key from the second storage after transmitting the encrypted access key stored in the second storage to the new agent. .

The trusted agent transmits the temporary public key, the encrypted access key, and ID information of the new agent to the server, and the server stores the temporary public key and the The ID information may be stored in association with the ID information, and the signature may be verified using the ID information.

A key sharing system according to one aspect of the present invention is a key sharing system in which an access key for accessing a database provided in a server is shared by a plurality of agents, and a trusted agent having the access key uses the access key a transmission unit that transmits the temporary public key and the encrypted access key to the server; and a temporary public key that corresponds to the temporary public key. an exporter for exporting a private key, the server comprising: a first storage for storing the temporary public key received from the trusted agent; and the encrypted access received from the trusted agent. an import unit for importing the temporary private key exported by the trusted agent; and a second storage unit for storing the imported temporary private key. a signature transmission unit for generating a signature using the a signature verification unit that verifies using a temporary public key; and a transmission unit that transmits the encrypted access key stored in the second storage unit to the new agent when the signature verification is successful. , wherein the new agent further comprises a decryption unit for decrypting the encrypted access key received from the server with the imported temporary private key.

An agent terminal according to one aspect of the present invention is an agent terminal in a key sharing system in which a plurality of agents share an access key for accessing a database provided in a server, and functions as a trusted agent having the access key. an encryption unit that encrypts the access key with a temporary public key used when sharing the access key; a transmission unit that transmits the temporary public key and the encrypted access key to the server; an exporter for exporting a temporary private key corresponding to a temporary public key, and an importer for importing the temporary private key exported by the trusted agent when functioning as a new agent without the access key. a signature transmission unit that generates a signature using the imported temporary private key and transmits the generated signature to the server; and the encrypted encrypted It is characterized by comprising a decryption unit that receives an access key and decrypts the received encrypted access key with the imported temporary secret key.

According to the present invention, an operator does not need to go back and forth between different environments multiple times, and the work load in key sharing processing can be reduced.

1 is a block diagram showing an example of functional configuration of a database management system; FIG. A block diagram explaining the relationship between the trusted agent, the new entrant agent, and the server of the database management system. FIG. 10 is a block diagram showing an example of the functional configuration in processing for an agent to enter the database management system; FIG. 10 is a sequence diagram showing an example of the operation of processing for an agent to enter the database management system;

1. Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an example of the functional configuration of processing in which an agent, which is a client, accesses a server database in the client-server database management system of the present invention.

The database management system consists of agents 110 and servers 120 .

The agent 110 includes a private key storage area 111 , an access key storage area 112 , an access key encryption section 113 , a database (DB) access request generation section 114 , a DB access request transmission section 115 and a data reception section 116 .

A private key of the agent 110 is stored in the private key storage area 111 . The access key storage area 112 stores an access key for accessing the DB 125 constructed on the server 120 . Access key encryption unit 113 encrypts the access key stored in access key storage area 112 using the secret key stored in secret key storage area 111 to generate an encrypted access key. The DB access request generation unit 114 generates a DB access request including the encrypted access key generated by the access key encryption unit 113 and a statement written in the query language of the DB 125 . The DB access request transmission unit 115 transmits the DB access request generated by the DB access request generation unit 114 to the server 120 . Then, the data receiving unit 116 receives data transmitted from the server 120 as a response to the DB access request.

The server 120 includes a public key storage area 121 , a DB access request receiver 122 , an encrypted access key decryptor 123 , a DB accesser 124 , a DB 125 and a data transmitter 126 .

The public key storage area 121 stores the public key of the agent 110 . The DB access request receiving unit 122 receives DB access requests transmitted from the agent 110 . The encrypted access key decryption unit 123 decrypts the encrypted access key included in the received DB access request into an access key for the DB 125 using the public key of the agent 110 stored in the public key. The DB access unit 124 accesses the DB 125 using the decrypted access key, and acquires data from the DB 125 or updates the DB 125 in accordance with the command written in the query language of the DB 125 included in the received DB access request. , destroy the access key. The data transmission unit 126 transmits data acquired from the DB to the agent 110 .

In this database management system, in order for the agent 110 to access the DB 125 of the server 120, the agent's public key must be registered in the server 120 and the access key must be stored in the agent. An agent whose public key has already been registered with the server 120 and has the access key of the DB 125 is called a trusted agent. An agent whose public key is not registered in the server 120 and does not have an access key for the DB 125 is called a new entry agent. A method of registering the public key of the new entry agent in the server 120 and sharing the access key of the DB 125 between the new entry agent and the new entry agent will be described.

FIG. 2 is a diagram illustrating the relationship between the trusted agent 200, the new entry agent 300, and the server 400 of the database management system.

The server 400 is software that operates on hardware provided by a cloud service provider. Trusted agent 200 and server 400 are connected via Internet 500 . Similarly, new entry agent 300 and server 400 are connected via Internet 500 . The trusted agent 200 and the new entrant agent 300 can be installed at any location as long as the environment allows connection to the Internet 500 .

1.2 Functional configuration of processing in which a new entry agent enters FIG. 3 shows an example of the functional configuration of the trusted agent 200, the new entry agent 300, and the server 400 in the processing in which the new entry agent 300 enters in the database management system. It is a functional block diagram.

The trusted agent 200 comprises an access key storage area 201 , an ID issuing section 202 , a key generating section 203 , an encrypting section 204 , a key exporting section 205 and a key transmitting section 206 .

The access key storage area 201 stores an access key for accessing a DB (not shown) of the server 400 . The access key storage area 201 has the same configuration as the access key storage area 112 in FIG.

The ID issuing unit 202 issues the ID of the new entry agent 300 . The ID is a number unique to each agent for identifying the agent.

The key generation unit 203 generates a set of a temporary public key and a temporary private key that the new entry agent 300 temporarily uses.

The encryption unit 204 encrypts the access key stored in the access key storage area 201 using the temporary public key generated by the key generation unit 203 to generate an encrypted access key.

The key export unit 205 exports the ID of the new entry agent issued by the ID issuing unit 202 and the temporary public key and temporary private key generated by the key generating unit 203 . The key export unit 205 saves the ID, temporary public key, and temporary private key in the removable media 600, for example.

The key transmission unit 206 transmits the ID of the new entry agent issued by the ID issuing unit 202 , the temporary public key generated by the key generation unit 203 , and the encrypted access key generated by the encryption unit 204 to the server 400 .

The new entry agent 300 includes a key import unit 301, a public key/private key storage area 302, a signature generation unit 303, an access key acquisition request generation unit 304, an access key acquisition request transmission unit 305, an encrypted access key It comprises a receiving unit 306 , an encrypted access key decrypting unit 307 , an access key storage area 308 , a key generating unit 309 , a key update request generating unit 310 and a key update request transmitting unit 311 .

The key import unit 301 imports the ID, temporary public key, and temporary private key generated and exported by the trusted agent 200 . For example, the ID, temporary public key, and temporary private key stored in the removable medium 600 are acquired and stored in the public key/private key storage area 302 .

A signature generation unit 303 generates a signature using the temporary private key stored in the public key/private key storage area 302 .

The access key acquisition request generation unit 304 generates an access key acquisition request including the signature generated by the signature generation unit 303 and the ID stored in the public key/private key storage area 302 .

The access key acquisition request transmission unit 305 transmits the access key acquisition request generated by the access key acquisition request generation unit 304 to the server 400 .

The encrypted access key reception unit 306 receives the encrypted access key transmitted as a response to the access key acquisition request by the server 400 that has successfully verified the signature included in the access key acquisition request.

The encrypted access key decrypting unit 307 decrypts the encrypted access key using the temporary secret key saved in the public key/private key saving area 302 and saves it in the access key saving area 308 .

A key generation unit 309 generates an authorized public key and an authorized private key. Also, after the temporary public key of the new entry agent registered in the server 400 is updated to the regular public key, the key generation unit 309 generates the temporary public key stored in the public key/private key storage area 302 . Update the key and temporary private key to the regular public key and regular private key.

The key update request generation unit 310 generates the regular public key generated by the key generation unit 309, the ID stored in the public key/private key storage area 302, and the temporary private key stored in the public key/private key storage area 302. Generate a key update request containing the signature generated using

Key update request transmission unit 311 transmits the key update request generated by key update request generation unit 310 to server 400 .

The server 400 includes a key reception unit 401, a public key storage area 402, an encrypted access key temporary storage area 403, an access key acquisition request reception unit 404, a signature verification unit 405, and an encrypted access key transmission unit 406. , a key update request reception unit 407 and a key update unit 408 .

Key receiving unit 401 receives an ID, a temporary public key, and an encrypted access key from trusted agent 200, associates the ID with the temporary public key, stores them in public key storage area 402, and stores the ID and the encrypted access key. They are stored in the encrypted access key temporary storage area 403 in association with each other.

The access key acquisition request receiving unit 404 receives an access key acquisition request from the new entry agent 300 .

Signature verification unit 405 acquires the temporary public key associated with the ID included in the received access key acquisition request from public key storage area 402, and uses the acquired temporary public key to obtain the ID included in the received access key acquisition request. Perform signature verification.

The encrypted access key transmission unit 406 transmits the encrypted access key stored in the encrypted access key temporary storage area 403 to the new entry agent 300 when the signature verification unit 405 successfully verifies the signature. After transmission, the encrypted access key stored in the encrypted access key temporary storage area 403 is deleted.

The key update request receiving unit 407 receives a key update request from the new entry agent 300 .

The key updating unit 408 acquires the temporary public key associated with the ID included in the received access key acquisition request from the public key storage area 402, and uses the acquired temporary public key to access the key included in the received access key acquisition request. Perform signature verification. When the signature verification is successful, the key update unit 408 updates the temporary public key stored in the public key storage area 402 with the regular public key included in the key update request.

1.3 Operation of New Entry Agent Entry Processing The operations of trusted agent 200, new entry agent 300, and server 400 in the entry processing of new entry agent 300 in the database management system will be described with reference to FIG.

First, the ID issuing unit 202 of the trusted agent 200 issues the ID of the new entry agent 300 (step S101).

The key generation unit 203 of the trusted agent 200 generates a pair of a temporary public key and a temporary private key temporarily used by the new entry agent 300 (step S102).

The encryption unit 204 of the trusted agent 200 encrypts the access key stored in the access key storage area 201 using the temporary public key generated by the key generation unit 203 to generate an encrypted access key (step S103).

The key transmission unit 206 of the trusted agent 200 transmits the ID of the new entry agent issued by the ID issuing unit 202, the temporary public key generated by the key generation unit 203, and the encrypted access key generated by the encryption unit 204 to the server. 400 (step S104).

The key receiving unit 401 of the server 400 receives the ID, the temporary public key, and the encrypted access key from the trusted agent 200, associates the ID with the temporary public key, and stores it in the public key storage area 402 (step S301). and the encrypted access key are stored in the encrypted access key temporary storage area 403 (step S302).

The key export unit 205 of the trusted agent 200 exports the ID of the new entry agent issued by the ID issuing unit 202 and the temporary public key and temporary private key generated by the key generating unit 203 (step S105).

The ID, temporary public key and temporary private key generated and exported by the trusted agent 200 are imported by the key import unit 301 of the new entry agent 300 and stored in the public/private key storage area 302 .

The signature generation unit 303 of the new entry agent 300 generates a signature using the temporary private key stored in the public key/private key storage area 302 (step S201).

The access key acquisition request generation unit 304 of the new entry agent 300 generates an access key acquisition request including the signature generated by the signature generation unit 303 and the ID stored in the public key/private key storage area 302, and generates the access key acquisition request. The transmission unit 305 transmits the access key acquisition request generated by the access key acquisition request generation unit 304 to the server 400 (step S202).

The access key acquisition request is received by access key acquisition request receiving section 404 of server 400 .

Signature verification unit 405 of server 400 acquires the temporary public key associated with the ID included in the received access key acquisition request from public key storage area 402, and uses the acquired temporary public key to verify the received access key acquisition request. is verified (step S303).

The encrypted access key transmission unit 406 of the server 400 transmits the encrypted access key stored in the encrypted access key temporary storage area 403 to the new entry agent 300 when the signature verification unit 405 successfully verifies the signature. (step S304).

After the encrypted access key is transmitted, the encrypted access key stored in the encrypted access key temporary storage area 403 is deleted (step S305).

The encrypted access key is received by the encrypted access key reception unit 306 of the new entrant agent 300 .

The encrypted access key decryption unit 307 of the new entry agent 300 decrypts the encrypted access key using the temporary secret key stored in the public key/private key storage area 302, and stores the encrypted access key in the access key storage area 308 (step S203).

The key generation unit 309 of the new entry agent 300 generates a regular public key and a regular private key (step S204).

The key update request generation unit 310 of the new entry agent 300 generates the regular public key generated by the key generation unit 309, the ID stored in the public key/private key storage area 302, and the public key/private key storage area 302. Generate a key update request containing a signature generated using the temporary private key obtained. Then, the key update request transmission unit 311 of the new entry agent 300 transmits the key update request generated by the key update request generation unit 310 to the server 400 (step S205).

The key update request is received by key update request receiving section 407 of server 400 .

Key updating unit 408 of server 400 acquires the temporary public key associated with the ID included in the received access key acquisition request from public key storage area 402, and uses the acquired temporary public key to update the received access key acquisition request. Verifies the signature contained in the . When the signature verification is successful, the key update unit 408 replaces the temporary public key stored in the public key storage area 402 with the regular public key included in the key update request (step S306).

Key updating unit 408 of server 400 sends information indicating that the temporary public key stored in public key storage area 402 has been successfully updated to the regular public key to new entry agent 300 as a response to the access key acquisition request. (step S307).

After receiving the information indicating that the public key has been successfully updated, the key generation unit 309 of the new entrant agent 300 converts the temporary public key and temporary private key stored in the public key/private key storage area 302 into a regular The public key and regular private key are updated (step S206).

By operating in this way, the database management system implements the process of entry by the new entry agent 300 .

1.4 Effect According to the database management system of the present invention, even when a new agent enters with only one work difference, the environment where the trusted agent is placed and the environment where the new entry agent is placed come and go. can be completed in one go. As a result, the work load on the worker can be reduced.

Further, in this embodiment, the server 400 is configured to delete the encrypted access key stored on the server 400 after transmitting the encrypted access key to the new entry agent 300 . As a result, even if the ID, temporary public key, and temporary private key of the new entry agent are stolen, after the legitimate new entry agent obtains the encrypted access key from the server 400, the unauthorized terminal can Obtaining the encrypted access key can be prevented. In addition, even if an unauthorized terminal acquires an encrypted access key from the server 400 using the stolen ID, temporary public key, and temporary private key before the legitimate new entry agent 300 obtains the encrypted access key, the new entry agent 300 is encrypted. Since the access key cannot be obtained, it is possible to quickly recognize that the encrypted access key has been passed to an unauthorized terminal.
2. Supplementation Although the present invention has been described above based on the embodiments, the present invention is of course not limited to the above-described embodiments, and the following modifications are conceivable.

(1) In the above-described embodiment, the trusted agent 200 stores the ID, temporary public key and temporary private key in the removable media 600, but the method of exporting the ID, temporary public key and temporary private key is is not. For example, it may be attached to an e-mail and sent to the new entry agent, or may be sent to the new entry agent using a communication protocol such as FTP. Also, if private line communication is available between the trusted agent 200 and the new entry agent 300, it may be used.

(2) The server 400 is configured to delete the encrypted access key from the server 400 after transmitting the encrypted access key to the new entry agent 300 . This is because the encrypted access key is not passed to multiple agents in order to minimize the damage even if the temporary private key of the new entry agent 300 is stolen. If this purpose can be achieved, the configuration of server 400 is not limited to this. For example, after transmitting the encrypted access key to the new entrant agent 300, the server 400 may prohibit access to the encrypted access key temporary storage area 403, and may not accept subsequent encrypted access key acquisition requests.

(3) Data sent from the agent 110 (trusted agent 200, new entry agent 300) to the server 120 (server 400) is given a signature generated using the agent's private key, and the server , any communication that does not successfully verify the signature may be discarded.

Further, communication between agent 110 (trusted agent 200, new entrant agent 300) and server 120 (server 400) may be encrypted. Data may be encrypted using public key cryptography, or a session key (common key) encrypted by public key cryptography may be shared at the start of communication, and the session key may be used for data encryption.

Known algorithms such as RSA encryption, DSA, ECDSA, and Elgamal signature can be used for the encryption algorithm, signature generation algorithm, and signature verification algorithm.

(4) Although the trusted agent 200 generates the temporary public key and the temporary private key, the temporary public key and the temporary private key may be issued by the key manager. Also, although the new entry agent 300 generates the authorized public key and authorized private key, the authorized public key and authorized private key may be issued by the key manager.

(5) The agent 110 (trusted agent 200, new entrant agent 300) is implemented, for example, by executing a computer program stored in a memory by the processor of a general-purpose computer. Each functional unit (secret key storage area 111, access key storage area 112, access key encryption unit 113, DB access request generation unit 114, DB access request transmission unit 115, data reception unit 116, access key storage area 201, ID issuing unit 202, key generation unit 203, encryption unit 204, key export unit 205, key transmission unit 206, key import unit 301, public/private key storage area 302, signature generation unit 303, access key acquisition request generation unit 304, access key acquisition request transmission unit 305, encrypted access key reception unit 306, encrypted access key decryption unit 307, access key storage area 308, key generation unit 309, key update request generation unit 310, key update request transmission unit 311 ), the agent may be composed of a terminal composed of an integrated circuit having a function equivalent to that of the agent.

The server 120 (server 400) is realized, for example, by executing a computer program stored in memory by a processor of a general-purpose computer.

Here, the computer program is constructed by combining a plurality of instruction codes indicating instructions to the computer in order to achieve a predetermined function.

Also, the computer program may be recorded on a computer-readable recording medium such as a flexible disk, hard disk, optical disk, semiconductor memory, or the like.

Also, the computer program may be transmitted via a wireless or wired telecommunication line, a network represented by the Internet, data broadcasting, or the like.

(6) The above embodiments and modifications may be combined.

INDUSTRIAL APPLICABILITY The present invention is useful in a database management system in which a server has a database that can be accessed with a single access key, and the access key is not held by the server but held only by the agent.

200 trusted agent 201 access key storage area 202 ID issuing unit 203 key generation unit 204 encryption unit 205 key export unit 206 key transmission unit 300 new entry agent 301 key import unit 302 secret key storage area 303 signature generation unit 304 access key acquisition Request generation unit 305 Access key acquisition request transmission unit 306 Encrypted access key reception unit 307 Encrypted access key decryption unit 308 Access key storage area 309 Key generation unit 310 Key update request generation unit 311 Key update request transmission unit 400 Server 401 Key reception Unit 402 Public key storage area 403 Encrypted access key temporary storage area 404 Access key acquisition request reception unit 405 Signature verification unit 406 Encrypted access key transmission unit 407 Key update request reception unit 408 Key update unit

Claims (6)

A key sharing method in which multiple agents share an access key for accessing a database provided by a server,
A trusted agent having the access key encrypts the access key with a temporary public key temporarily used when sharing the access key, and transmits the temporary public key and the encrypted access key to the server. , exporting a temporary private key corresponding to said temporary public key;
the server storing the temporary public key received from the trusted agent in a first storage unit and storing the encrypted access key received from the trusted agent in a second storage unit;
A new agent without the access key imports the temporary private key exported by the trusted agent, generates a signature using the imported temporary private key, and sends the generated signature to the server;
The server verifies the signature received from the new agent using the temporary public key stored in the first storage unit, and stores the signature in the second storage unit if the signature verification is successful. sending the encrypted access key to the new agent;
A key sharing method, wherein the new agent decrypts the encrypted access key received from the server with the imported temporary private key. After obtaining the access key, the new agent transmits to the server an agent public key used for secure communication with the server,
2. The key sharing method according to claim 1, wherein said server replaces said temporary public key stored in said first storage unit with said agent public key. The server deletes the encrypted access key from the second storage unit after transmitting the encrypted access key stored in the second storage unit to the new agent. 3. The key sharing method according to claim 1 or 2, wherein the trusted agent sending the temporary public key, the encrypted access key and the identity information of the new agent to the server;
4. The server associates and stores the temporary public key and the ID information in the first storage unit, and verifies the signature using the ID information. A key agreement method according to any one of A key sharing system in which multiple agents share an access key for accessing a database provided by a server,
A trusted agent having the access key includes: an encryption unit that encrypts the access key with a temporary public key that is temporarily used when sharing the access key; a transmission unit for transmitting to the server; and an export unit for exporting a temporary private key corresponding to the temporary public key,
The server has a first storage unit for storing the temporary public key received from the trusted agent and a second storage unit for storing the encrypted access key received from the trusted agent. prepared,
The new agent that does not have the access key has an import unit that imports the temporary secret key exported by the trusted agent, generates a signature using the imported temporary secret key, and sends the generated signature to the server. a signature sending unit for sending;
The server further includes: a signature verification unit that verifies the signature received from the new agent using the temporary public key stored in the first storage unit; a transmission unit for transmitting the encrypted access key stored in the storage unit of 2 to the new agent;
The key sharing system, wherein the new agent further comprises a decryption unit that decrypts the encrypted access key received from the server with the imported temporary secret key. An agent terminal in a key sharing system in which multiple agents share an access key for accessing a database provided by a server,
When functioning as a trusted agent having the access key, an encryption unit that encrypts the access key with a temporary public key that is temporarily used when sharing the access key; a transmission unit that transmits the access key to the server; and an export unit that exports a temporary private key corresponding to the temporary public key,
When functioning as a new agent that does not have the access key, the import unit imports the temporary private key exported by the trusted agent, and the imported temporary private key is used to generate a signature, and the generated signature to the server, receives the encrypted access key that is transmitted when the server successfully verifies the signature, and imports the received encrypted access key An agent terminal, comprising a decryption unit that decrypts with the temporary private key.

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