JP4697255B2 - Gateway device - Google Patents

Description

  The present invention relates to a gateway device, and more particularly to a gateway device that receives an e-mail addressed to a client device from a mail server device and distributes the received e-mail to the client device in response to a mail reception request command from the client device. About.

  Since electronic mail has advantages such as convenience and quickness, electronic data such as text data and image data is often transmitted and received using electronic mail in the field of business. However, since the electronic mail is transmitted through an unspecified communication path, there is a possibility that the electronic mail is wiretapped, falsified, and impersonated during the transmission. In order to solve such security problems, e-mail encryption according to the prior art in which e-mail is encrypted using a public key encryption method such as S / MIME (Secure / Multipurpose Internet Mail Extensions) A system has been proposed.

  For example, in Patent Documents 1 to 4, plaintext email received from each client device is encrypted and transmitted to the mail server device, and encrypted email received from the mail server device is decrypted into plaintext email to each client. A gateway device that transmits to a device is disclosed. By using such a gateway device, it is possible to improve the safety of sending and receiving electronic mail.

Japanese Patent Laid-Open No. 11-275881. Japanese Patent Application Laid-Open No. 2004-104567. JP-A-11-175419. Japanese Patent Application Laid-Open No. 11-163925.

  For example, in the mail processing system described in Patent Document 2, a customer-side mail server corresponding to the gateway device connects to the mail server device at a regular timing, and receives and stores an email addressed to the client device. Thereafter, the customer-side mail server delivers the stored electronic mail to the client device in response to a command requesting reception of the electronic mail from the client device. Therefore, even if the user of the client device wants to receive an email immediately, the next connection timing from the customer side mail server to the mail server device will arrive even if the above command is manually sent to the customer side mail server. Until then, there has been a problem that the client device cannot receive the electronic mail stored in the mail server device.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a gateway device that can quickly deliver an electronic mail stored in a mail server device to a client device as compared with the prior art.

The gateway device according to the present invention stores, in a storage device, e-mails addressed to all client devices received from the mail server device at predetermined time intervals, and responds to a mail reception request command from the client device in response to the client device. In a gateway device comprising a control means for distributing the electronic mail stored in the device,
The control means is characterized in that an electronic mail is received from the mail server apparatus in response to the mail reception request command and stored in a storage device.

  In the gateway device, when the control means receives an e-mail from the mail server device in response to the mail reception request command, it receives only an e-mail addressed to a specific client device that has transmitted the mail reception request command. It is characterized by doing.

  In the gateway device, the control unit may receive a mail reception request command from the specific client device and receive only an e-mail addressed to the specific client device and store it in the storage device. When the next mail reception request command is received from the specific client device, further reception of electronic mail from the mail server device is stopped.

  Still further, in the gateway device, the email is an encrypted email, and the control means receives the encrypted email from the mail server device, decrypts it into a plain text email, and stores it in the storage device. Then, in response to the mail reception request command from the client device, the stored plain text electronic mail is distributed to the client device.

  According to the gateway device according to the present invention, e-mails addressed to all client devices received from the mail server device at predetermined time intervals are stored in the storage device, and in response to a mail reception request command from the client device, In the gateway device comprising control means for delivering the stored electronic mail to the client device, the control means receives the electronic mail from the mail server device in response to the mail reception request command and stores it in the storage device. Store. Therefore, the gateway device according to the present invention receives an e-mail from the mail server device at the timing when the mail reception request command is received from the client device in addition to the timing at every predetermined time interval. Thus, the electronic mail stored in the mail server device can be quickly distributed to the client device.

  Further, in the gateway device, when the control means receives the encrypted electronic mail from the mail server device in response to the mail reception request command, the control unit sends an encryption addressed to the specific client device that transmitted the mail reception request command. Only receive structured emails. Therefore, the load applied to the gateway device can be reduced as compared with the gateway device.

  Furthermore, in the gateway device, after receiving the mail reception request command from the specific client device, the control means receives only the encrypted electronic mail addressed to the specific client device and decrypts it into plain text electronic mail. When the next mail reception request command is received from the specific client device before it is stored in the storage device, further reception of the encrypted electronic mail from the mail server device is stopped. Therefore, the load on the gateway device can be further reduced as compared with the gateway device.

  Still further, in the gateway device, the email is an encrypted email, and the control means receives the encrypted email from the mail server device, decrypts it into a plain text email, and stores it in the storage device. In response to the mail reception request command from the client device, the stored plain text electronic mail is distributed to the client device. Therefore, it is possible to improve the safety of transmission / reception of electronic mail as compared with the gateway device.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

First embodiment.
FIG. 1 shows a local area network (hereinafter referred to as a LAN) including an S / MIME gateway device 20 having a function of transmitting and receiving an electronic mail using S / MIME according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration.

  The LAN system according to this embodiment includes a plurality of N client personal computers 30-1 to 30-N (hereinafter collectively referred to as reference numeral 30), an S / MIME gateway device 20, a router device 60, A mail server device 40 connected to the Internet 90 is connected via a LAN 70. 2 to 4 are block diagrams showing configurations of the client personal computer 30, the S / MIME gateway device 20, and the mail server device 40 of FIG. 1, respectively. The configurations of the LAN system, client personal computer 30, S / MIME gateway device 20, and mail server device 40 shown in FIGS. 1 to 4 are applied to the first to third embodiments.

  Each client personal computer 30 is configured to be able to send and receive e-mails encrypted using S / MIME by connecting to the mail server device 40 via the S / MIME gateway device 20 and the router device 60. .

  Transmission of plain text e-mail from each client personal computer 30 is performed as follows. First, each client personal computer 30 transmits the created plain text electronic mail to the S / MIME gateway device 20. The S / MIME gateway apparatus 20 converts the plain text e-mail received from each client personal computer 30 into an encrypted e-mail with an electronic signature by performing an encryption process and an electronic signature process using the S / MIME. To do. Further, the S / MIME gateway device 20 transmits the encrypted electronic mail with the electronic signature to the mail server 40 via the router device 60.

  Further, the delivery of the electronic mail to each client personal computer 30 by the S / MIME gateway device 20 is performed as follows. The main control unit 1 (see FIG. 3) of the S / MIME gateway apparatus 20 receives e-mails addressed to all the client personal computers 30-1 to 30-N from the mail server apparatus 40 at predetermined time intervals. Here, the electronic mail received from the mail server device 40 includes plain text electronic mail and encrypted electronic mail with an electronic signature. Further, the main control unit 1 determines, for each received email, whether the email is a plain text email or an encrypted email with an electronic signature based on the header portion of the email. Then, the plaintext e-mail is stored in the mailboxes 8-1 to 8-N (see FIG. 3) as it is, while the encrypted e-mail with the electronic signature is subjected to the electronic signature verification process and the decryption process, and the plaintext e-mail is obtained. And stored in the mailboxes 8-1 to 8-N. Further, in response to each first mail reception request command from each client personal computer 30-1 to 30-N, the stored plain text electronic mail is distributed. In the present embodiment, the main control unit 1 of the S / MIME gateway device 20 receives an e-mail from the mail server device 40 in response to the first mail reception request command and sends it to the mailboxes 8-1 to 8-N. It is characterized by storing. The delivery of e-mail to each client personal computer 30 by the S / MIME gateway device 20 will be described later in detail with reference to FIG.

  Next, the configuration of the client personal computer 30 will be described with reference to FIG.

  In FIG. 2, a client personal computer 30 is an external terminal device that is a known personal computer, and executes processing such as generation, recording, storage, transmission, and reception of plain text e-mail, image data, and character data. The client personal computer 30 is used as a client device, and transmits the generated plain text electronic mail to the S / MIME gateway device 20. In addition, the client personal computer 30 transmits a first mail reception request command for requesting reception of an electronic mail to the S / MIME gateway apparatus 20 and is transmitted from the S / MIME gateway apparatus 20 in response thereto. Receive plain text emails. The first mail reception request command is generated at predetermined time intervals or according to a predetermined instruction command for instructing reception of an e-mail input by the user of the client personal computer 30 via the operation unit 105. .

  The e-mail transmission / reception program of the client personal computer 30 is stored in the hard disk drive 108 of the client personal computer 30 in advance. The e-mail transmission / reception program is a known control program for creating an e-mail and transmitting / receiving an e-mail via the S / MIME gateway apparatus 20.

  The main control unit 101 is specifically composed of a CPU (Central Processing Unit) and is connected to the following hardware units via the bus 113 to control them and execute various software functions. . The display unit 104 is a display device such as a liquid crystal display device (LCD (Liquid Crystal Display)) or a CRT (Cathode Ray Tube) display, and displays the operating state of the client personal computer 30, e-mail to be sent and received The displayed e-mail. The operation unit 105 is, for example, a keyboard, and is used for inputting an instruction command for receiving character data and an e-mail.

  A ROM (Read Only Memory) 106 stores various software programs necessary for the operation of the client personal computer 30 and executed by the main control unit 101 in advance. A RAM (Random Access Memory) 107 is composed of SRAM (Static RAM), DRAM (Dynamic RAM), SDRAM (Synchronous DRAM), etc., and is used as a working area of the main control unit 101 and is generated when a program is executed. Store temporary data. Further, the hard disk drive 108 is a storage device that incorporates a recording medium, and stores an application program to be executed and an image memory. In the first to third embodiments, the hard disk drive 108 stores the e-mail transmission / reception program of the client personal computer 30 as described above. Further, the LAN interface 112 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. .

  Next, the configuration of the S / MIME gateway apparatus 20 will be described with reference to FIG.

  The S / MIME gateway apparatus 20 has an electronic mail transmission / reception function. In the e-mail transmission / reception function of the S / MIME gateway device 20, plain text e-mail received from each client personal computer 30 is subjected to electronic signature processing and encryption processing by software according to S / MIME, and then sent to the mail server device 40. Sent. As will be described in detail later, the S / MIME gateway device 20 generates a second mail reception request command for requesting transmission of e-mail addressed to all the client personal computers 30, and sends it to the mail server device 40. Sent. Of the emails received from the mail server device 40 in response to this, plain text emails are left as they are, and a plurality of N mailboxes 8-1 to 8 provided for each of the client personal computers 30-1 to 30-N. -N (hereinafter collectively referred to as 8), the encrypted electronic mail with electronic signature is converted into plain text electronic mail by performing electronic signature verification processing and decryption processing by software according to S / MIME. And stored in the mailbox 8. Further, as will be described later, the electronic mail stored in the mailbox 8 is delivered to each client personal computer 30 in response to a first mail reception request command from each client personal computer 30. That is, the S / MIME gateway device 20 functions as an SMTP (Simple Mail Transfer Protocol) server device and a POP3 (Post Office Protocol Ver. 3) server device for each client personal computer 30 and also an SMTP client device for the mail server device 40. And function as a POP3 client device.

  In the S / MIME gateway device 20, the main control unit 1 is specifically composed of a CPU and is connected to the following hardware units via the bus 13 to control them, and various software described later. Perform the function. The ROM 6 stores in advance various software programs such as a BIOS (Basic Input / Output System) that are necessary for operations such as activation of the S / MIME gateway device 20 and executed by the main control unit 1. The RAM 7 is composed of SRAM, DRAM, SDRAM or the like, and is used as a working area for the main control unit 1 to store temporary data generated when the program is executed.

  Further, the hard disk drive 9 is a storage device having a built-in recording medium, and stores various data and programs. In the present embodiment, at least the program of the e-mail transmission / reception process (FIG. 5) of the S / MIME gateway device 20 including. The hard disk drive 9 stores the plain text e-mail received from the mail server device 40 and the plain text e-mail generated from the received encrypted e-mail with the electronic signature for each of the client personal computers 30-1 to 30-N. N mailboxes 8-1 to 8-N are included. The LAN interface 12 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. . Further, when a predetermined time-up time (for example, 10 minutes) has elapsed since the timer circuit 5 was reset, the timer circuit 5 transmits a control signal indicating the time-up to the main control unit 1.

  Next, the configuration of the mail server device 40 will be described with reference to FIG.

  In FIG. 4, a mail server device 40 is a well-known mail server device, and executes e-mail transmission / reception processing. The mail server device 40 transmits the encrypted electronic mail with the electronic signature from the S / MIME gateway device 20 to the destination mail server device (not shown) via the Internet 90. In addition, the mail server device 40 stores e-mails (including plain text e-mails and encrypted e-mails with electronic signatures) from a mail server device (not shown) as a transmission source in the mail box 402. Further, in response to the second mail reception request command from the S / MIME gateway device 20, the e-mail addressed to all the client personal computers 30 is transmitted to the S / MIME gateway device 20. The e-mail transmission / reception program of the mail server device 40 is stored in the hard disk drive 408 in advance. The e-mail transmission / reception program is a known control program for transmitting / receiving e-mail to / from the S / MIME gateway device 20.

  The main control unit 101 is specifically composed of a CPU and is connected to the following hardware units via the bus 413 to control them and execute various software functions. The display unit 104 is a display device such as a liquid crystal display device (LCD) or a CRT display, and displays the operation state of the mail server device 40. The operation unit 405 is, for example, a keyboard, and is used for inputting character data and instruction commands.

  The ROM 406 stores various software programs that are necessary for the operation of the mail server device 40 and executed by the main control unit 401 in advance. The RAM 407 is composed of SRAM, DRAM, SDRAM, etc., and is used as a working area for the main control unit 401 to store temporary data generated when the program is executed. Further, the hard disk drive 408 is a storage device that incorporates a recording medium, and stores an application program to be executed and an image memory. In the first to third embodiments, the hard disk drive 408 stores an e-mail transmission / reception program as described above. The hard disk drive 408 includes a mail box 402. Further, the interface 414 is connected to the Internet 90 and receives signals and data from the Internet 90, while transmitting signals and data to the Internet 90 to perform interface processing related to Internet communication such as signal conversion and protocol conversion. Execute. The LAN interface 412 is connected to the LAN 70 and receives signals and data from the LAN 70, and transmits signals and data to the LAN 70 to execute interface processing related to LAN communication such as signal conversion and protocol conversion. .

  FIG. 5 is a flowchart showing an e-mail transmission / reception process according to the first embodiment, which is executed by the main control unit 1 of the S / MIME gateway device 20 of FIG.

  In FIG. 5, first, in step S1, the timer circuit 5 is reset, and the process proceeds to step S2. In step S2, it is determined whether or not a predetermined time-up time has elapsed and a control signal indicating the time-up has been received from the timer circuit 5. If YES, the process proceeds to step S6. If NO, Proceed to step S3. Next, in step S3, it is determined whether or not a first mail reception request command has been received from one client personal computer 30. If NO, the process returns to step S2, while if YES, the process proceeds to step S4. In step S4, it is determined whether or not the plain text e-mail addressed to the client personal computer 30 that has transmitted the first mail reception request command is in the mail box 8. If YES, the process proceeds to step S5. If NO, Proceed to step S6.

  Next, in step S5, the plain text e-mail addressed to the client personal computer 30 that has transmitted the first mail reception request command is distributed to the client personal computer 30, and the process proceeds to step S6. In step S <b> 6, a second mail reception request command for requesting reception of e-mails addressed to all client personal computers 30 is transmitted to the mail server device 40. Next, in step S7, e-mails addressed to all client personal computers 30 transmitted from the main control unit 401 of the mail server device 40 in response to the first mail reception request command are received. Here, the received electronic mail includes plain text electronic mail and encrypted electronic mail with electronic signature. Further, in step S8, each received encrypted electronic mail with an electronic signature is subjected to decryption processing and signature verification processing in accordance with S / MIME, and each plain text electronic mail and the received plain text electronic mail are processed. Store in the mailbox 8 and return to step S1.

  As described above in detail, according to the S / MIME gateway device 20 according to the present embodiment, the main control unit 1 determines that a predetermined time-up time has elapsed since the timer circuit 5 was reset (step in FIG. 5). When the first mail reception request command is received from the client personal computer 30 (in the case of YES in step S3 in FIG. 5), in addition to the response in the first mail reception request command. Then, the second mail reception request command is transmitted to the mail server device 40 (step S6 in FIG. 5), and e-mails addressed to all the client personal computers 30 are received from the mail server device 40. Further, the main control unit 1 stores the plain text e-mail out of the received e-mails in the mail box 8 as it is, and decrypts the encrypted e-mail with the electronic signature into the plain text e-mail and stores it in the mail box 8. . Therefore, compared with the prior art, the encrypted electronic mail with electronic signature stored in the mail server device 40 can be converted into plain text electronic mail, and can be quickly distributed to the client personal computer 30.

Second embodiment.
The second embodiment according to the present invention is characterized in that the hard disk drive 9 of the S / MIME gateway apparatus 20 stores the program of the e-mail transmission / reception process of FIG. 6 as compared with the first embodiment. Here, the e-mail transmission / reception processing program of FIG. 6 is obtained by adding steps S9 and S10 to the e-mail transmission / reception processing program according to the first embodiment of FIG. Other configurations are the same as those of the first embodiment.

  FIG. 6 is a flowchart showing an e-mail transmission / reception process according to the second embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG.

  In FIG. 6, first, in step S1, the timer circuit 5 is reset, and the process proceeds to step S2. In step S2, it is determined whether a predetermined time-up time has elapsed and a control signal indicating the time-up has been received from the timer circuit 5. If YES in step S2, as in the first embodiment (see FIG. 5), the process proceeds to step S6, and a second mail reception request command for requesting reception of e-mails addressed to all client personal computers 30. Is transmitted to the mail server device 40. Next, in step S7, e-mails addressed to all client personal computers 30 transmitted from the main control unit 401 of the mail server device 40 in response to the first mail reception request command are received. Here, the received electronic mail includes plain text electronic mail and encrypted electronic mail with electronic signature. In step S8, decryption processing and signature verification processing are performed on each received encrypted electronic mail with electronic signature in accordance with S / MIME, and each plain text electronic mail and the received plain text electronic mail after processing are mailboxed. 8 and returns to step S1.

  On the other hand, if NO in step S2, the process proceeds to step S3. In step S3, it is determined whether or not a first mail reception request command has been received from one client personal computer 30. If NO, the process returns to step S2, while if YES, the process proceeds to step S4. In step S4, it is determined whether or not the plain text e-mail addressed to the client personal computer 30 that has transmitted the first mail reception request command is in the mail box 8. If YES, the process proceeds to step S5. If NO, Proceed to step S9. Next, in step S5, the plain text e-mail addressed to the client personal computer 30 that transmitted the first mail reception request command is distributed to the client personal computer 30, and the process proceeds to step S9.

  In step S9, a third mail reception request command including an identifier for designating the client personal computer 30 that has transmitted the first mail reception request command and requesting reception of an electronic mail addressed to the client personal computer 30 is generated. It transmits to the server apparatus 40. In response to this, the main control unit 401 of the mail server device 40 transmits an e-mail addressed to the predetermined client personal computer 30 designated in the third mail reception request command to the S / MIME gateway device 20. . Next, in step S10, the electronic mail addressed to the client personal computer 30 that has transmitted the first mail reception request command is transmitted from the main control unit 401 of the mail server device 40, and the process proceeds to step S8.

  According to the S / MIME gateway apparatus 20 according to the first embodiment, for example, when the user of each client personal computer 30 needs to receive e-mail relatively frequently, or the number of client personal computers 30 is relatively As a result, when the first mail reception request command is transmitted relatively frequently from each client personal computer 30 to the S / MIME gateway apparatus 20, the following problem occurs. That is, every time the S / MIME gateway device 20 receives the first mail reception request command from each client personal computer 30, the S / MIME gateway device 20 transmits the second mail reception request command to the mail server device 40, so that all clients Since an e-mail addressed to the personal computer 30 is received from the mail server device 40, there arises a problem that a relatively large load is applied to the S / MIME gateway device 20, the Internet 90, and the LAN 70.

On the other hand, the S / MIME gateway device 20 according to the second embodiment is characterized in that it operates as follows compared to the first embodiment.
(A) Like the first embodiment, a second mail reception request command is transmitted to the mail server device 40 at every predetermined time-up time (step S6 in FIG. 6), and all client personal computers are transmitted. The e-mail addressed to 30 is received from the mail server device 40 (step S7 in FIG. 6).
(B) When the first mail reception request command is received from the specific client personal computer 30, the third mail reception request command is transmitted to the mail server device 40 (step S9 in FIG. 6). Only the e-mail addressed to the client personal computer 30 is received from the mail server device 40 (step S10 in FIG. 6).

  Therefore, according to the S / MIME gateway apparatus 20 according to the second embodiment, the load on the S / MIME gateway apparatus 20, the Internet 90, and the LAN 70 can be reduced as compared with the first embodiment.

Third embodiment.
The third embodiment according to the present invention is characterized in that the hard disk drive 9 of the S / MIME gateway apparatus 20 stores the program of the e-mail transmission / reception process of FIG. 7 as compared with the second embodiment. Other configurations are the same as those of the second embodiment.

  FIG. 7 is a flowchart showing an e-mail transmission / reception process according to the third embodiment, which is executed by the main control unit 1 of the S / MIME gateway apparatus 20 of FIG.

  In FIG. 7, first, in step S11, flags Fn (n = 1, 2,..., N) relating to all client personal computers 30 are set to zero, and the process proceeds to step S1. Here, the flag Fk is a flag indicating whether or not the processing of steps S14 to S19 described later is being executed for the kth client personal computer 30-k, and has a value of 1 when it is being executed. If it is not running, it has a value of 0.

  Next, in step S1, the timer circuit 5 is reset, and the process proceeds to step S2. In step S2, it is determined whether a predetermined time-up time has elapsed and a control signal indicating the time-up has been received from the timer circuit 5. If “YES” in the step S2, the process proceeds to a step S6 as in the first and second embodiments (see FIGS. 5 and 6) to request reception of e-mails addressed to all the client personal computers 30. 2 is sent to the mail server device 40. Next, in step S7, e-mails addressed to all client personal computers 30 transmitted from the main control unit 401 of the mail server device 40 in response to the first mail reception request command are received. Here, the received electronic mail includes plain text electronic mail and encrypted electronic mail with electronic signature. Further, in step S8, each received encrypted electronic mail with an electronic signature is subjected to decryption processing and signature verification processing in accordance with S / MIME, and each plain text electronic mail and the received plain text electronic mail are processed. Store in the mailbox 8 and return to step S1.

  On the other hand, if NO in step S2, the process proceeds to step S3. In step S3, it is determined whether or not a first mail reception request command has been received from one client personal computer 30. If NO, the process returns to step S2, while if YES, the process proceeds to step S12. Here, the client personal computer 30 that has transmitted the first mail reception request command is referred to as a client personal computer 30-k. In step S12, it is determined whether or not the flag Fk related to the client personal computer 30-k is 0. If NO, the process returns to step S2, while if YES, the process proceeds to step S13. In step S14, the flag Fk is set to 1, and the process proceeds to step S14. In step S14, it is determined whether or not a plain text e-mail addressed to the client personal computer 30-k is in the mail box 8-k. If YES, the process proceeds to step S15. If NO, the process proceeds to step S16. Next, in step S15, the plain text e-mail addressed to the client personal computer 30-k is distributed to the client personal computer 30-k, and the process proceeds to step S16.

  Next, in step S16, a third mail reception request command including an identifier designating the client personal computer 30-k and requesting reception of an electronic mail addressed to the client personal computer 30-k is generated, and the mail server device 40 is notified. Send. In response to this, the main control unit 401 of the mail server device 40 transmits an e-mail addressed to the client personal computer 30-k designated in the third mail reception request command to the S / MIME gateway device 20. . Next, in step S17, an e-mail addressed to the client personal computer 30-k transmitted from the main control unit 401 of the mail server device 40 is received, and the process proceeds to step S18. Here, the received electronic mail includes plain text electronic mail and encrypted electronic mail with electronic signature. Further, in step S18, each received encrypted mail with an electronic signature is subjected to decryption processing and signature verification processing according to S / MIME, and the processed plaintext email and the received plaintext email are mailed. Store in box 8-k and proceed to step S19. Next, in step S19, the flag Fk is set to 0, and the process returns to step S1.

  As described above in detail, the S / MIME gateway apparatus 20 according to the third embodiment receives the first mail reception request command from the specific client personal computer 30-k, and then addresses the client personal computer 30-k. When the next first mail reception request command is received from the client personal computer 30-k during the period from receiving only the electronic mail to storing it in the mailbox 8-k, the electronic mail is sent from the mail server device 40. Furthermore, it stops receiving. Therefore, as compared with the second embodiment, even when the first mail reception request command is continuously transmitted from the specific client personal computer 30-k to the S / MIME gateway apparatus 20, the S / MIME is also transmitted. The load on the gateway device 20 can be reduced.

  In each of the above embodiments, the S / MIME gateway device 20 performs encryption processing and electronic signature processing on each electronic mail from the client personal computer 30 according to S / MIMEN, and from the mail server device 40. Although the decryption process and the electronic signature verification process are performed on each electronic mail, the present invention is not limited to this. For example, the S / MIME gateway device 20 may be configured to perform the encryption process and the decryption process and not perform the electronic signature process and the electronic signature verification process. Further, instead of the S / MIME gateway device 20, encryption processing and electronic signature processing are performed on each electronic mail from the client personal computer 30 according to PGP (Pretty Good Privacy) / MIME, while from the mail server device 40, It may be a gateway device that performs decryption processing and electronic signature verification processing on each electronic mail.

  As described above in detail, according to the gateway device of the present invention, e-mails addressed to all client devices received from the mail server device at every predetermined time interval are stored in the storage device, and mails are received from the client devices. In a gateway device comprising control means for delivering the stored electronic mail to the client device in response to a request command, the control means sends an electronic mail from the mail server device in response to the mail reception request command. Is stored in the storage device. Therefore, the gateway device according to the present invention receives an e-mail from the mail server device at the timing when the mail reception request command is received from the client device in addition to the timing at every predetermined time interval. Thus, the electronic mail stored in the mail server device can be quickly distributed to the client device.

It is a block diagram which shows the structure of the LAN system provided with the S / MIME gateway apparatus 20 which has a function which transmits / receives an email using S / MIME which is the 1st Embodiment of this invention. It is a block diagram which shows the structure of the client personal computer 30 of FIG. It is a block diagram which shows the structure of the S / MIME gateway apparatus 20 of FIG. It is a block diagram which shows the structure of the mail server apparatus 40 of FIG. It is a flowchart which shows the email transmission / reception process which concerns on 1st Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the email transmission / reception process which concerns on 2nd Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG. It is a flowchart which shows the email transmission / reception process based on 3rd Embodiment performed by the main control part 1 of the S / MIME gateway apparatus 20 of FIG.

Explanation of symbols

1 ... main control part,
5 ... Timer circuit,
6 ... ROM,
7 ... RAM,
8, 8-1 to 8-N ... Mailbox,
9 ... Hard disk drive,
12 ... LAN interface,
13 ... Bus
20 ... S / MIME gateway device,
30, 30-1 thru | or 30-N ... client personal computer,
40. Mail server device,
60: Router device,
70: Local area network (LAN),
90 ... Internet.

Claims (2)

E-mails addressed to all client devices received from the mail server device at predetermined time intervals are stored in the storage device, and the e-mail stored in the client device in response to a mail reception request command from the client device In a gateway device provided with a control means for distributing
Said control means is responsive to the mail reception request command, only e-mail for a specific client device addressed to send the mail reception request command, and receive e-mail from the mail server device stored in the storage device ,
The control means receives the mail reception request command from the specific client device and then receives only the e-mail addressed to the specific client device and stores it in the storage device from the specific client device. A gateway device characterized in that, when a next mail reception request command is received, further reception of electronic mail from the mail server device is stopped . The email is an encrypted email,
The control means receives the encrypted electronic mail from the mail server device, decrypts it into plain text electronic mail, stores it in the storage device, and responds to the mail reception request command from the client device in response to the client claim 1 Symbol placement of the gateway device, characterized in that delivering the stored plain text email device.

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