JP2005141461A - Encryption communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encryption communication system for solving such a problem of increase in communication traffic by eliminating necessity of indicating an encryption method and a shared key at each transmission and reception of encrypted mails. <P>SOLUTION: One communication terminal device F1 transmits an electronic mail inquiring a prescribed encryption capability. On the other hand, another communication terminal device F2 replies encryption capability information, such as a prepared encryption method and a public key via electronic mail when the electronic mail inquiring the capability is received. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a communication system for sending and receiving electronic mail.

2. Description of the Related Art Conventionally, in an Internet facsimile machine, electronic mail can be transmitted / received to / from a communication terminal on the other side. This is shown in Patent Document 1 below. This can send and receive encrypted e-mails, but with this one, both the sending side and the receiving side hold the encryption method, common key, and secret key, and Then, the encryption method and the common key are taught to request transmission of the encrypted mail, and the other party encrypts and sends the email based on the taught encryption method and the common key. The receiving apparatus decrypts the received encrypted mail using a secret key corresponding to the taught common key.
JP 11-215383 A

  In the above-described conventional electronic mail terminal device, it is necessary to teach its own encryption method and common key every time transmission of encrypted mail is requested, so it takes time to send and receive encrypted mail. It took time. Furthermore, each time an encrypted mail is sent and received, an encryption method and a large-sized common key must be sent, causing problems such as an increase in communication traffic and an increase in communication time.

  The present invention has been proposed in view of the above circumstances, and eliminates the necessity of teaching the encryption method and the common key every time an encrypted mail is sent and received, thereby solving various problems such as an increase in communication traffic. An object of the present invention is to provide an encrypted communication system that can be eliminated.

  In order to achieve the above object, in claim 1, a predetermined encryption capability inquiry e-mail is transmitted from one communication terminal apparatus, while the other communication terminal apparatus receives the inquiry e-mail. It is characterized in that encryption capability information such as an encryption method and a public key prepared in advance is returned by e-mail.

  In claim 2, when one communication terminal device receives the encryption capability information from the other communication terminal device in response to the encryption capability inquiry e-mail, the received encryption capability information is transmitted to the communication terminal device. The address is added to the address and automatically registered in a predetermined encryption capability information registration table prepared in advance.

  In claim 3, when one communication terminal device receives an instruction to encrypt an e-mail designating a transmission destination, the communication terminal apparatus reads out the encryption capability information stored in the encryption capability information registration table and sends the e-mail. It is characterized by being transmitted after being encrypted.

  According to claim 1 of the present invention, a predetermined encryption capability inquiry e-mail is transmitted from one communication terminal apparatus, while the other communication terminal apparatus prepares in advance when the inquiry e-mail is received. The encryption capability information such as the encryption method and the public key is returned by e-mail.

  Accordingly, in one communication terminal device, if the encryption capability information from the other communication terminal device is received, the encryption capability information of the other communication terminal device can be known, and if this is stored, the encryption capability information can be obtained. Each time a computerized e-mail is sent to the other communication terminal device, it is not necessary to send the encryption method and a large common key from the other, reducing communication time and communication traffic. .

  In claim 2, when one communication terminal device receives the encryption capability information from the other communication terminal device in response to the encryption capability inquiry e-mail, the received encryption capability information is transmitted to the communication terminal device. The address is added to the address and automatically registered in a predetermined encryption capability information registration table prepared in advance.

  Therefore, once the other party is inquired about the encryption method and public key, the subsequent encrypted communication can be determined simply by referring to the encryption capability table without obtaining such information from the other party. Communication time can be shortened and communication traffic can be reduced.

  In claim 3, when one communication terminal device receives an instruction to encrypt an e-mail designating a transmission destination, the communication terminal apparatus reads out the encryption capability information stored in the encryption capability information registration table and sends the e-mail. It is characterized by being transmitted after being encrypted.

  Therefore, once the other party is inquired about the encryption method and public key, the subsequent encrypted communication can be determined simply by referring to the encryption capability table without obtaining such information from the other party. Communication time can be shortened and communication traffic can be reduced.

  Embodiments of the present invention will be described below.

  FIG. 1 is a diagram showing an example of a schematic configuration of an encrypted communication system according to the present invention. In this apparatus, an Internet facsimile apparatus F1 and an Internet facsimile apparatus F2 constituting a communication terminal apparatus are connected by a communication network N1 such as the Internet N1.

  FIG. 2 is a diagram showing an example of a main part configuration of a communication terminal device used in this system. Here, the configuration of the Internet facsimile machine F is shown as an example of the communication terminal apparatus, but the present invention is not limited to this example, and may be a communication terminal such as a personal computer having an e-mail transmission / reception function.

  The Internet facsimile machines F1 and F2 control the facsimile machines F1 and F2. The CPU 1 constituting the control means of the present invention, the NCU 2 for controlling connection to the telephone line L connected to the public line network N1, and the facsimile communication. The modem 3 that modulates and demodulates various signals necessary for this purpose, the ROM 4 that stores programs necessary for the operation of the facsimile apparatus F, abbreviated dials, and the like are registered, and an encryption capability information registration table (registered later) is registered. And a RAM 5 in which an encryption method unique to the apparatus F, a common key, and a secret key are registered, a scanner 6 that reads a set original and forms image data, and a codec (not shown). ) Is composed of an image memory 7 for storing the image data encoded by the above and a liquid crystal screen, etc. A display unit 8, an operation unit 9 constituted by various operation keys, a printer 10 for recording image data on a preset recording sheet and discharging it to a discharge tray, and this facsimile apparatus F to a network N1 through a LAN. A LAN interface 11 for connection, a mail tray 12 including a transmitted mail tray 12A for storing transmitted mail and a received mail tray 12B for storing received mail, and an encryption / decryption unit 13 are provided.

  The encryption / decryption unit 13 encrypts an electronic mail to be transmitted by processing to be described later. Also, the received encrypted electronic mail is decrypted with a pre-registered secret key.

  The encryption capability information table T5A included in the RAM 5 has a configuration as shown in FIG. 3, and the encryption method and public key data correspond to each other's communication address (here, e-mail address). It is supposed to be registered. Here, RSA, PSA, and ECC are illustrated as encryption methods, but the present invention is not limited to this example.

  The facsimile machines F1 and F2 perform the processing shown in the flowchart of FIG. 4 when receiving an electronic mail from the other party. Various flows will be described below. Here, for the sake of easy understanding, the transmission side (one communication terminal device in the claims) of the encrypted electronic mail is set to the facsimile apparatus F1, the encrypted electronic mail. The receiving side (the other communication terminal device in the claims) is a facsimile machine F2.

  When the other facsimile apparatus F2 receives the new mail (100, 101), it stores the new mail (100, 101), discriminates the type of the mail (102), and if it is a normal electronic mail, the process is terminated. If the encryption information request mail from the apparatus F1, that is, the inquiry mail of the encryption capability, if the encryption capability is effectively registered in the own device F2 (103), the own device F2 can perform encrypted communication. Therefore, the encryption capability of the facsimile apparatus F1 on the transmission side of the encrypted electronic mail is extracted from the request mail and stored (104). Then, the facsimile apparatus F2 teaches the facsimile apparatus F1 its own encryption method and public key by e-mail (105).

  On the other hand, if the encryption capability is not effectively registered in the device F2, an e-mail teaching that the encryption capability cannot be taught is transmitted (106).

  The encryption information request mail notifies the other device that it is inquiring about the encryption capability. For example, the notification information can be sent by adding a predetermined code to the continuation of the title. What is necessary is just to be able to notify that. Such an encryption information request mail is created on the side of the facsimile apparatus F1 that is the main body of the encrypted mail transmission, and as shown in the flowchart of FIG. 5, the facsimile apparatus F1 sends an instruction to transmit the encryption information request mail by a predetermined operation. Then (200), the facsimile machine F1 creates an encryption information request mail with a predetermined code by the CPU 1, and transmits the mail designating the other apparatus F2 (201).

  It should be noted that such encryption information request mail includes not only the inquiry about the encryption capability but also the encryption capability information (encryption method, public key) specific to the requesting facsimile machine F1. May be. Then, the facsimile machine F2 that has received this request mail can store the encryption capability of the facsimile machine F1.

  When the other device F2 receives the request mail transmitted in steps 200 to 201, the encryption capability information is received by the one device F1 by the processing of steps 100 to 105. Therefore, the device F1 receives the request mail. The communication address of the apparatus F2 is extracted from the received e-mail, and the received encryption method and public key are registered in the encryption capability information table 5A in association with the address.

  In this way, when the encryption method and the public key are registered in the encryption capability information table 5A, the processing shown in the flowchart of FIG. 6 can be performed in one device F1. That is, if an instruction to send an e-mail is given (300), it is determined whether or not it is with an instruction to send an encrypted e-mail (301).

  Then, if there is an instruction for encrypted mail, the encryption capability information registration table 5A is referred to, the encryption method and the common key corresponding to the communication address of the destination are extracted, and the encrypted electronic mail is sent based on these. Create and send (304, 305). On the other hand, if there is no instruction for encrypted e-mail (301), normal e-mail is created and transmitted without encryption processing (305).

  Then, when extraction of the encryption capability corresponding to all destinations requested to be encrypted and creation / transmission of the encrypted mail are completed, a warning is output (306, 307).

  The apparatus of the present invention can be applied to all communication systems that transmit and receive electronic mail.

The figure which shows an example of schematic structure of this invention system The figure which shows an example of the internal structure of the facsimile apparatus used by this invention The figure which shows an example of a structure of an encryption capability information table. Flowchart for explaining processing to be performed on the reception side of encrypted mail (teaching encryption capability information) Flow chart for explaining the processing to be performed on the encrypted mail transmission side (encryption capability inquiry) It is a flowchart for demonstrating preparation of an encryption mail, and a transmission process.

Explanation of symbols

F1, F2 ... Internet facsimile machine 5A ... Encryption capability table 1 ... CPU
5 ... RAM

Claims (3)

In a communication system for sending and receiving e-mail,
One communication terminal device transmits a predetermined encryption capability inquiry e-mail, while the other communication terminal device receives an inquiry e-mail such as an encryption method and a public key prepared in advance. An encryption communication system, wherein the encryption capability information is returned by e-mail. In claim 1,
When the one communication terminal device receives the encryption capability information from the other communication terminal device in response to the encryption capability inquiry e-mail, the received encryption capability information is changed to the communication address of the communication terminal device. The encryption communication system is configured to be automatically registered in a predetermined encryption capability information registration table prepared in advance. In claim 1 or 2,
When one of the communication terminal devices receives an instruction to encrypt an e-mail specifying a transmission destination, it reads out the encryption capability information stored in the encryption capability information registration table and encrypts the e-mail. An encrypted communication system, characterized by transmitting.

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