JP2002149569A - Cryptographic communication system, cryptographic communication method and computer program - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To distribute an encryption / decryption key (private key) unique to a broadcast list of an e-mail to a user and to perform encryption. In a cryptographic communication system including a plurality of sender / receiver computers interconnected by a communication network and a server computer having a broadcast mail function, a server 1 receives a request from a sender computer and designates the request in a broadcast list. Means 2 for sending an e-mail to the specified recipient, means 3 for modifying the broadcast list based on the request of the sender, means 4 for managing the environment of the sender and receiver, and reception specified in the broadcast list. Means 5 for generating a common encryption / decryption key to be sent to a user.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
More particularly, the present invention relates to an encryption communication system, an encryption communication method, and a computer program used for encrypting a broadcast mail in an intranet.

[0002]

2. Description of the Related Art When an electronic mail is transmitted after being encrypted, the sender uses a receiver's encryption key prepared in advance and encrypts the electronic mail for each sender. Further, when an unspecified number of recipients, that is, the other party cannot be identified, as in a broadcast mail, the e-mail is transmitted without being encrypted. Japanese Patent Laid-Open No. 7-66803 discloses a technique in which a shared encryption key g1 is decrypted with a conversation key a.

[0003]

However, in the above-mentioned prior art, in the transmission of an electronic mail, for a mail in which the receiver can be specified from the sender, the encryption key (public key) of the other party is obtained in advance and the individual encryption is performed. Can be transmitted. However, in the case of broadcast mail (mailing list, alias, etc.), the receiver cannot be identified from the sender, and the other party cannot be specified. Therefore, the encryption key (public key) cannot be obtained, and the sender encrypts the message. Can not be applied. Also, if the system side encrypts using the encryption key for each recipient at the time of sending mail, the encryption processing in the system will increase, and the machine will be overloaded, making it difficult to send and receive mail smoothly. I will. The present invention has been made in view of the above circumstances, and provides a user with an encryption / decryption key (private key) unique to an e-mail distribution list and a generation ID indicating a generation attached to the encryption / decryption key (private key) to a user. An encryption communication system, an encryption communication method, and a computer program to be distributed are provided.

[0004]

In order to solve the above problems, in a cryptographic communication system comprising a plurality of sender / receiver computers interconnected by a communication network and a server computer having a broadcast mail function, the server comprises: Means for modifying the distribution list based on the request of the sender, means for managing the environment of the sender and receiver, and generation of a common encryption / decryption key to be sent to recipients registered in the modified distribution list And a means for transmitting the generated common encryption / decryption key to a recipient registered in a broadcast list by mail. Therefore, according to the present invention, it is possible to give confidentiality to mail in the cryptographic communication system, and it is possible to transmit and receive messages between broadcast list registrants without leaking to the outside. (2) An encryption communication method for encrypting and transmitting an e-mail through a server computer in response to a request from a sender's computer in order to solve the above-described problem. Receiving, extracting the sender's encryption key from the database, extracting the common encryption / decryption key for the latest broadcast mail from the database, and sending the common encryption / decryption key and the ID indicating its generation to the sender. An encryption communication method, comprising: encrypting with an encryption key; and transmitting the encrypted key and ID to a registration request source.

Therefore, according to the present invention, it is possible to give confidentiality to mail in the cryptographic communication system, and it is possible to transmit and receive messages between broadcast list registrants without leaking to the outside. (3) In order to solve the above problem, the present invention is a computer program for encrypting and transmitting an e-mail through a server computer in response to a request from the computer of the sender, and transmitting the mail from the computer of the sender. A function of receiving a list registration request, a function of extracting a sender's encryption key from a database, a function of extracting a common encryption / decryption key for the latest broadcast mail from a database, a common encryption / decryption key, and an ID indicating its generation Is a computer program for realizing a function of encrypting a password with an encryption key of a sender and a function of transmitting the encrypted key and ID to a registration request source. Therefore, according to the present invention, it is possible to give confidentiality to mail in the cryptographic communication system, and it is possible to transmit and receive messages between broadcast list registrants without leaking to the outside.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the cryptographic communication system according to the present invention. In the figure, a server 1 includes a mail server unit 2, a broadcast processing unit 3, a user management unit 4, a key generation unit 5, and a database 6, and a client 11, a client 12,... I have. The mail server unit 2 receives a mail from a user of the client and transmits the mail to the specified user. The broadcast processing unit 3 registers, updates, and deletes a broadcast list, and sends an e-mail to the registered user of the broadcast list through the mail server unit 2. The user management unit 4 manages a user's mail address and manages an encryption key (public key).
The key generation unit 5 includes an encryption / decryption key (private key) dedicated to the broadcast list.
Is generated. The database 6 stores a user's encryption key (public key), a broadcast mail encryption / decryption key (private key), a broadcast list, and the like. FIG. 2 is a diagram showing an exchange when a user A on the client 11 requests the server 1 to register in a broadcast list. First, the user A on the client 11 requests the mail server unit 2 to register in the broadcast list (1).

The mail server unit 2 notifies the broadcast processing unit 3 that a registration request has been received from the user A (2). The broadcast processing unit 3 queries the user management unit 4 for the user A (3). The user management unit 4 searches the database 6 for the encryption key (public key) of the user A (4), sends the encryption key (public key) of the user A to the key generation unit 5, and stores the existing latest broadcast mail. Request for an encryption / decryption key (secret key) (5). The key generation unit 5 stores the encryption / decryption key (private key) stored in the database in advance and the generation ID indicating the generation assigned to the encryption / decryption key (private key) in the user A
(7), and replies to the user A on the client 11 through the mail server unit 2 (8). Then, the user A decrypts the received mail with the decryption key (personal key) possessed only by the user A, and indicates the encryption / decryption key (secret key) and the generation attached to the encryption / decryption key (private key). The generation ID is stored and managed. On the other hand, if the encryption key (public key) of the user A exists in the database 6, the user management unit 4 notifies the broadcast processing unit 3 of the fact (9). The broadcast processing unit 3 adds the user A to the broadcast list (10). Similarly, users B,..., And user N can be registered in the distribution list in the same manner as described above by a registration request to the mail server unit 2, and the encryption / decryption key (secret key) and its encryption / decryption key ( The generation ID indicating the generation attached to the (secret key) is stored and managed.

FIG. 3 is a diagram showing an operation of a registration request to a broadcast list. First, the server 1 receives a broadcast list registration request from the user A on the client 11 (S
1), and extracts the encryption key (public key) of the user A from the database 6 (S2). Next, an encryption / decryption key (secret key) for the latest broadcast mail is extracted from the database 6 (S
3). Here, the extracted encryption / decryption key (secret key) includes:
A generation ID indicating a generation is assigned. Next, the encryption / decryption key (private key) and the generation ID indicating the generation attached to the encryption / decryption key (secret key) are encrypted with the encryption key (public key) of the user A (S4), and the registration request source Is returned to the user A (S5). This completes the registration in the broadcast list. FIG. 4 shows the user A on the client 11
FIG. 7 is a diagram showing an exchange when sending an e-mail to a user registered in a broadcast list from a server to a server 1. First, the user A on the client 11 uses the latest stored encryption / decryption key (private key) for broadcast mail, encrypts the mail to be transmitted, and transmits the mail to the mail server unit 2 to the broadcast list. Make a request (11). Mail server 2
Requests the broadcast processing unit 3 to perform broadcast processing (12). The broadcast processing unit 3 searches the broadcast list (13), requests the mail server unit 2 to transmit to the broadcast list (14), and sends the encrypted mail to the user registered in the broadcast list. It is transmitted (15).

The receiving user decrypts the received mail with the latest broadcast mail encryption / decryption key (secret key). FIG. 5 is a diagram illustrating an operation of transmitting an e-mail to a user registered in the broadcast list. First, the client 11
Upon receiving a request for transmission of a mail encrypted by using the latest broadcast mail encryption / decryption key (secret key) stored by the user A from the above user A (S11), the database 6 receives the request. The broadcast list is searched (S12), and the encrypted mail is transmitted to the users registered in the broadcast list (S12).
13). FIG. 6 is a diagram showing an exchange when a user A on the client 11 requests the server 1 to delete the broadcast list. First, the user A on the client 11 requests the mail server unit 2 to delete the broadcast list (21). The mail server unit 2 notifies the broadcast processing unit 3 that the user A has received a deletion request (2
2). The broadcast processing unit 3 queries the user management unit 4 for the user A (23). When the user A exists in the broadcast list, the user management unit 4 sends a request to delete the user A from the broadcast list to the broadcast processing unit 3 (24), and sends a new encryption / decryption key to the key generation unit 5. A request to generate a (secret key) is made (25).

The broadcast processing unit 3 deletes the user A from the broadcast list (26). The key generation unit 5 generates a new encryption / decryption key (private key), updates a generation ID indicating the generation assigned to the new encryption / decryption key (secret key), and stores it in the database 6 ( 27). Further, the key generation unit 5 uses the new encryption / decryption key (secret key) and the updated generation ID indicating the generation attached to the encryption / decryption key (secret key) as the encryption key of each user other than the user A. (Public key), and broadcast processing unit 3 sends (28)
It is distributed to each user (29) through the mail server unit 2 (30). And the users other than the user A,
The received mail is decrypted with the decryption key (personal key) of each user, and the updated generation ID indicating the new encryption / decryption key (private key) and the generation attached to the encryption / decryption key (private key) is obtained. Save and manage. Similarly, user B, ...,
The user N can also be deleted from the broadcast list in the same manner as described above by requesting the mail server unit 2 to delete the broadcast list. FIG. 7 is a diagram showing the operation of a request to delete a broadcast list. First, the user A on the client 11
Receives a request to delete from the broadcast list (S31)
Then, the user A is deleted from the broadcast list (S32).

Next, a new encryption / decryption key (secret key) is generated (S33), and a generation ID indicating the generation assigned to the new encryption / decryption key (secret key) is updated. It is stored (S34). Next, the new generation ID indicating the new encryption / decryption key (secret key) and the generation attached to the encryption / decryption key (private key) is stored in the user A
(S35), and transmits to all the users (S3).
6). As described above, according to the present invention, confidentiality can be given to mail in the cryptographic communication system, and message transmission and reception between broadcast list registrants can be performed without leaking to the outside. The present invention is a cryptographic communication system in which a common encryption / decryption key (secret key) is changed when a certain event occurs to ensure security for a third party, and is transmitted to an unspecified partner. Security can be maintained by updating the encryption / decryption key (private key) at the appropriate timing. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

As described above, according to the present invention, confidentiality can be given to mail in a cryptographic communication system, and messages can be transmitted and received between broadcast list registrants without leaking to the outside. Become possible

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of an encryption communication system according to the present invention.

FIG. 2 is a view for explaining a communication operation of the cryptographic communication system shown in FIG. 1;

FIG. 3 is a view for explaining the operation of the cryptographic communication system shown in FIG. 2;

FIG. 4 is a view for explaining another communication operation of the cryptographic communication system shown in FIG. 1;

FIG. 5 is a view for explaining another operation of the cryptographic communication system shown in FIG. 4;

FIG. 6 is a view for explaining still another communication operation of the cryptographic communication system shown in FIG. 1;

FIG. 7 is an exemplary view for explaining still another operation of the cryptographic communication system shown in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Server 2 ... Mail server part 3 ... Broadcast processing part 4 ... User management part 5 ... Key generation part 6 ... Database

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04L 12/22 H04L 11/20 101B 11/26

Claims (6)

[Claims] 1. In a cryptographic communication system comprising a plurality of sender / receiver computers interconnected by a communication network and a server computer having a broadcast mail function, the server modifies a broadcast list based on a request from a sender. Means for managing the environment of the sender and receiver, means for generating a common encryption / decryption key to be sent to the recipient registered in the modified distribution list, and means for generating the common encryption / decryption key. Means for sending an e-mail to a recipient registered in the broadcast list. 2. The cipher according to claim 1, wherein the means for generating the common encryption / decryption key uses a common encryption / decryption key and a generation ID indicating the generation attached to the common encryption / decryption key. Communications system. 3. An encryption communication method for encrypting and transmitting an e-mail through a server computer in response to a request from a sender's computer, comprising the steps of: receiving a broadcast list registration request from the sender's computer; Extracting the sender's encryption key from the database, extracting the common encryption / decryption key for the latest broadcast mail from the database, and encrypting the common encryption / decryption key and the ID indicating its generation with the sender's encryption key. And a step of transmitting the encrypted key and ID to a registration request source. 4. An encryption communication method for performing a deletion process from a broadcast list in response to a request from a sender's computer, comprising the steps of: receiving a deletion request from a broadcast list from the sender's computer; Deleting a sender from the list, generating a new common encryption / decryption key, further updating an ID indicating a generation attached to the common encryption / decryption key, and generating the common encryption / decryption key. And encrypting the updated ID with an encryption key of each of the recipients registered in the broadcast list from which the sender has been deleted, and transmitting the encrypted ID. 5. A computer program for encrypting and transmitting an e-mail through a server computer in response to a request from a sender's computer, the computer program having a function of receiving a broadcast list registration request from the sender's computer, A function of extracting a sender's encryption key from a database, a function of extracting a common encryption / decryption key for the latest broadcast mail from a database, and encrypting a common encryption / decryption key and an ID indicating its generation with the sender's encryption key. A computer program for realizing a function and a function of transmitting the encrypted key and ID to a registration request source. 6. A computer program for performing a deletion process from a broadcast list in response to a request from a sender's computer, comprising: a function of receiving a request from the sender's computer to delete the broadcast list; And a new common encryption / decryption key is generated, and an I / O indicating the generation attached to the common encryption / decryption key is generated.
D and a function of updating the generated common encryption / decryption key and the updated ID with the encryption key of each of the recipients registered in the broadcast list from which the sender has been deleted,
A computer program that implements the function of transmitting.