JPH10247904A - Ciphered communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the leakage of message within a computer network even when a receiving telephone network terminal is a normal facsimile equipment by allowing a call originating computer terminal to encipher a message through the use of an intermediate equipment and key information and communicating between the intermediate equipment and a telephone network terminal without nonciphering. SOLUTION: A call originating computer 15 using an electronic mail device 21 acquires the open key of the intermediate equipment necessary for ciphering in advance and stores it in an information storing means 22. At the time of transmitting a message, the mail input means of a device 21 prepares a message and a ciphering means 23 ciphers it through the use of the open key of the equipment 13 stored in the storing means 22. The ciphered message is transmitted to the equipment 13 through the computer network by a communication control means 24. As the message is transmitted after ciphering the message is prevented form being leaded within the network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encrypted communication method for performing message communication between a computer network terminal and a telephone network terminal by encrypting the message so that the message is not leaked.

[0002]

2. Description of the Related Art As shown in FIG. 10, for example, an intermediate device (hereinafter simply referred to as an intermediate device) 13 between a telephone network and a computer network having interfaces to a public telephone network 11 and a computer network 12, respectively, is provided. , The telephone network terminal 14 of the telephone network 11 and the computer terminal 15 of the computer network 12
Communication of messages with one another via the Internet is performed.

[0003] As shown in FIG.
Sends the image data as e-mail to the intermediate device 13 through the computer network 12,
Reference numeral 3 converts the image data of the e-mail into facsimile data and transmits it to a normal facsimile terminal (telephone network terminal) 14 through the telephone network 11. In this manner, image data can be sent from the computer terminal 15 to the telephone network terminal 14.

Since communication on the computer network 12 is performed using a common line without setting a line between the computer terminals 15 accommodated in the computer network 12 and only the communication between them, the communication is leaked (wiretapping). ). Since the computer terminal 15 can easily and often be provided with an encryption / decryption means, as shown in FIG. , The encrypted message is transmitted to the normal facsimile terminal 14 via the telephone network 11, but cannot be received by the normal facsimile terminal 14. That is, communication leakage cannot be avoided by using the encryption function of the computer terminal 15. To use this encryption function, the telephone network terminal 1
As 4, it is necessary to provide a dedicated facsimile terminal capable of decrypting the encryption.

[0005] Further, as shown in FIG.
When a dedicated facsimile terminal 14 'having a function of decrypting a cipher is used as the reference numeral 4, a non-facsimile message, for example, a text is encrypted and transmitted as e-mail from the computer terminal 15, and the intermediate device 13 is transmitted to the destination telephone network terminal. 14 'is called and there is a response, and even if the encrypted message from the computer terminal 15 is transmitted to the dedicated facsimile terminal 14', the decrypted data is text data, which is displayed and output by the facsimile terminal 14 '. It is not possible.

[0006]

As described above, according to the conventional method, the originating computer terminal 15 of the computer network 12 has an encrypting means, and it is desired that the message is transmitted within the computer network 12 after being encrypted. Even in this case, as shown in FIG. 12A, when the receiving telephone network terminal is a normal facsimile machine 14, there is a problem that the encrypted message cannot be transmitted.

[0007] In addition, the recipient is a dedicated facsimile machine 1
Even when 4 'is used, the media conversion cannot be performed by the intermediate device 13, so if the originating computer terminal 15 encrypts and transmits a message other than facsimile,
There is a problem that the receiving telephone network terminal 14 'cannot display a message. Further, if a message is transmitted without being encrypted so that it can be received by the ordinary facsimile machine 14, there is a problem that the message is leaked in the computer network 12 as shown in FIG. Was.

According to the present invention, a message leaked in a computer network can be prevented even if the receiving telephone network terminal is an ordinary facsimile machine by decrypting the message encrypted by the originating computer terminal in the intermediate device. The present invention proposes an encrypted communication method capable of preventing such an encrypted communication.

[0009]

According to the present invention, an originating computer terminal of a computer network encrypts a message using key information of an intermediate device.
Even if the receiving telephone network terminal does not have an encryption / decryption function like a normal facsimile machine, or has a different type of encryption / decryption function than the originating computer terminal, the computer The present invention is characterized in that a message is encrypted and transmitted over a network so that the message can be used effectively.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1A shows Embodiment 1 of the present invention, in which a message is transmitted from a computer terminal 15 having an encryption function to a telephone network terminal 14 having no decryption function. The case will be described as an example.

The transmitting computer terminal 15 using the electronic mail device 21 acquires the public key of the intermediate device 13 necessary for encryption in advance and stores it in the information storage means 22. When transmitting a message, a message as shown in FIG. 2 is created by the mail input / output means of the electronic mail device 21. First, a sender address 61 is described, and then a format 62 (MIME version 1.0 in this example) of the following description is shown, followed by a destination (recipient) address 63, and a subject 64 is used in this example. Then Japanese JIS
The code describes the test, then content type 6
5 is a multipart / mixed boundary in this example.
742959F6218E ", with this boundary 66 added, indicates that the content type 67 is text / normal in this example, and that the character is a JIS standard code, and that the content conversion encoding 68 is a 7-bit code in this example. After indicating that there is, the message content text 69 is described.After the next boundary 70, the content type 71 is an image in this example, the format is gif, and the content conversion code is indicated. Is 72 in this example.
, The encoded image data 73 is described, and a boundary 74 is added at the end.

Such an electronic mail message is shown in FIG.
The encryption unit 23 in A uses the public key of the intermediate device 13 stored in the storage device 22 to perform encryption. The encrypted message is as shown in FIG. 3, for example. That is, the sender address 61, the description format 62, the recipient address 63, and the subject 64 are the same as before the encryption, and the next content format 65 is a multi-part. Next
Part Level 1-175350 ", and further indicates that the encryption protocol is pgp in this example. The next content type 67 on the boundary 66 is version 1 of pgp encryption in this example. The next content type 76 after the next boundary 75 indicates that the next is encrypted data, and the boundary 6 in FIG.
Data 7 from the end of 6 to the last boundary 64 is encrypted
7 is described, the encryption ends, and the process ends at the boundary 78.

The message thus encrypted is shown in FIG.
A is transmitted to the intermediate device 13 via the computer network 12 by the communication control means 24 in A. Since the message is transmitted after being encrypted, it is possible to prevent the message from leaking in the computer network 12. The encrypted message is received by the intermediate device 13 by the communication control means 26, and the message is decrypted by the decryption means 27 using the secret key. In this example, the decrypted message is converted into facsimile image data as shown in FIG. 4 by the media conversion means 28 of the intermediate device 13. The media-converted message is transmitted by the communication control means 29 via the telephone network 11 to the telephone network terminal, in this example, the normal facsimile terminal 1
4 is transmitted.

The facsimile terminal 14 has a communication control means 31
The facsimile is received by the
The facsimile image shown in FIG. 4, in this example, is reproduced and discharged onto a sheet. As is apparent from this figure, the media conversion means 28 of the intermediate device 13 converts the image message code 73 from the originating computer terminal 15 to a facsimile code, converts the text message 69 to a facsimile image code, and The facsimile data is created so that the subject "test" is displayed as an image in the upper left corner of the screen in both the text image and the message image. Therefore, even if the transmitting computer terminal 15 transmits a non-facsimile image message, the facsimile terminal 14 can receive the message as an image.

The communication between the root node 13 and the facsimile terminal 14 is via the telephone network 11. During the communication, a dedicated line is set between them, and other terminals cannot interrupt this line. That is, there is no risk of message leakage.
The above processing and signal flow are as shown in FIG. 1B. To briefly describe this again, the sending computer terminal 1
In step 5, the message is encrypted with the public key of the intermediate device and transmitted to the intermediate device 13. The intermediate device 13 decrypts the encrypted message (e-mail) with the private key, and further converts the media, that is, creates facsimile data. The receiving facsimile terminal 14 is called, and when there is a response from the terminal 14, facsimile data is transmitted to the terminal 14.

If the receiving telephone network terminal 14 is a data communication terminal or an e-mail device, the message from the originating computer terminal 15 is subjected to media conversion according to the receiving telephone network terminal 14, for example, image data is converted to text data. Also, the encoding method of text data is converted. If the receiving telephone network terminal 14 has a decryption function, the root node 13 extracts the public key of the receiving telephone network terminal 14 from the storage means 33, encrypts the decrypted message with the encrypting means 34, and performs communication. The data is transmitted from the control means 29 and decrypted by the receiving telephone network terminal 14 using the secret key of the terminal. The computer terminal 15 has a decoding means 25 to be used when it becomes a receiving telephone network terminal.

The computer terminal 15 is connected to the intermediate device 13
The public key is obtained, for example, as shown in FIG. The root node 13 generates a public key and its secret key, stores the secret key in the storage means 33, and registers the public key with the certificate authority 35 via the computer network 12. The computer terminal 15 acquires the public key of the root node 13 from the certificate authority 35 via the computer network 12 and stores it in the storage unit 22. The computer terminal 15 also generates a public key of the terminal 15 and a secret key thereof, stores the secret key in the storage means 22 and registers the public key in the certificate authority 35 via the computer network 12. Further, the user information of the computer terminal 15 is encrypted with the public key of the intermediate device 13 and sent to the intermediate device 13 via the computer network 12, and the intermediate device 13 decrypts the user information with its own secret key. Get. Intermediate device 1
3 obtains the public key of the terminal 15 from the certificate authority 35. Embodiment 2 In Embodiment 2 in FIG. 1A, a telephone network terminal 14 without an encryption function transmits a message to a computer terminal 15 with a decryption function. As shown in FIG. 5, the receiving computer terminal 15 first generates its own public key / private key pair, registers the public key with the certificate authority 35, and then obtains user information such as a name in advance. The encrypted data is encrypted using the public key of the root node 13 and sent to the root node 13. The intermediate device 13 acquires the public key of the receiving telephone network terminal 15 necessary for encryption from the certificate authority 35 using the user information, and stores the subscriber information storage means 3 in the intermediate device 13.
3 is stored.

When a message is transmitted from the facsimile terminal 14 to the computer terminal 15, a facsimile image as shown in FIG. The input facsimile image is transmitted to the root node 13 by the communication control means 31. That is, the originating computer terminal 14 sends the intermediate device 13
When there is an outgoing call, the communication control means 29 responds, and when a facsimile signal is transmitted from the transmitting computer terminal 14, the facsimile signal is received. The received facsimile signal is converted into an e-mail format by the media conversion means 28. This e-mail is, for example, as shown in FIG.
There are a sending address 61, a description format 62, a receiving address 63, and a subject 64 (in this example, FAX), and after the boundary 66 after the description of the content format 65, the one corresponding to the image message part in FIG. 2 follows. . The message converted to the e-mail format is stored in the subscriber information storage unit 33.
The encryption means 34 uses the extracted public key of the receiving telephone network terminal 15 to perform encryption. The encrypted message is transmitted to the computer terminal 15 by the communication control means 26. Since the message is transmitted after being encrypted, it is possible to prevent the message from leaking in the computer network 12. After receiving the message by the communication control unit 24, the receiving computer terminal 15 decrypts the message by the decryption unit 25 using its own private key.

If the receiving telephone network terminal 15 is not an e-mail device but a data communication terminal or a facsimile terminal, the intermediate device 1 is set in accordance with these terminal types.
The conversion is performed by the third media conversion means 28. Third Embodiment FIG. 9A shows a third embodiment of the present invention, in which a message communication between two computer terminals 15 having a public key encryption function is performed by a transmitting computer terminal and a receiving telephone network terminal. Is transmitted to the computer terminal 41.

The originating computer terminal 15 using the electronic mail device 21 obtains in advance the public key of the intermediate device 13 necessary for encryption in accordance with the sequence shown in FIG.
The information is stored in the server information storage unit 22. In addition, the receiving computer terminal 41 using the electronic mail device 28
Receiving telephone network terminal 4 required for encryption in intermediate device 13
The first public key is registered in the subscriber information storage means 33 of the root node 13 by, for example, the sequence shown in FIG.

After the message is created by the electronic mail device 21 of the sending computer terminal 15, the encrypting means 23 uses the public key of the intermediate device 13 stored in the storage means 22 for the message. And encrypt it. The encrypted message is transmitted by the communication control means 24 to the root node 13 via the computer network 12 as shown in FIG. 9B. Since the message is transmitted after being encrypted, it is possible to prevent the message from leaking in the computer network 12.

The intermediate device 13 receives the encrypted message by the communication control means 26, and decrypts the message by the decryption means 27 using the secret key of the intermediate device 13. The decrypted message is fetched from the subscriber information storage means 33 to obtain the extracted public key of the receiving telephone network terminal 41, and is encrypted by the encryption means. The encrypted message is transmitted by the communication control means 26 to the receiving computer terminal 41 via the computer network 12. Since the message is transmitted after being encrypted, it is possible to prevent the message from leaking in the computer network 12. After receiving the message by the communication control means 43, the receiving telephone network terminal 41 decrypts the message by the decrypting means 44 using its own secret key. Thus, the originating computer terminal 15
When the encryption method is different between the receiving computer terminal 41 and the transmitting computer terminal 15 or the transmitting computer terminal 15 does not know the key information of the receiving computer terminal 41, the message can be encrypted and transmitted in the computer network 12. Note that the decryption means 45 corresponding to the encryption means 42 is provided in the intermediate device 13, and the computer terminal 4
1, a storage means 46 and an encryption means 47 are provided.

[0023]

As described above, according to the first aspect of the present invention, in transmitting a message from a computer network, it is possible to prevent message leakage in the computer network and improve the convenience of the sender. effective. Further, according to the second aspect of the present invention, in transmitting a message from the telephone network in the intermediate device, it is possible to prevent message leakage in the computer network, and there is an effect of improving convenience for the caller. According to the third aspect of the invention, messages can be transmitted and received even if the transmitting computer terminal and the receiving computer terminal use different encryption methods.

[Brief description of the drawings]

FIG. 1A is a block diagram showing an example of a system to which an embodiment of the present invention is applied, and FIG. 1B is a diagram showing a sequence of the embodiment of the present invention.

FIG. 2 is a diagram showing an example of a message created by a sending computer terminal.

FIG. 3 is a view showing an example of a message transmitted from a computer terminal which has encrypted the message shown in FIG. 2;

FIG. 4 is a diagram showing an example in which a message from a computer terminal is converted into a facsimile image.

FIG. 5 is a diagram showing an example of a public key acquisition sequence.

FIG. 6 is a diagram showing a sequence according to the second embodiment.

FIG. 7 is a diagram illustrating an example of an image transmitted from a facsimile terminal.

FIG. 8 is a view showing an example of a message in which a facsimile image received by an intermediate device is subjected to media conversion which can be received by a computer terminal.

FIG. 9A is a block diagram illustrating a system example to which the third embodiment is applied, and FIG. 9B is a diagram illustrating a sequence example of the third embodiment;

FIG. 10 is a diagram showing an example of a network system to which the present invention is applied.

FIG. 11 is a diagram showing a message transfer sequence from a conventional computer terminal to a normal facsimile terminal.

12A is a diagram showing a sequence when an encrypted message is transmitted from a conventional computer terminal to a normal facsimile terminal, and FIG. 12B is a sequence when a non-facsimile message is transmitted from a conventional computer terminal to a dedicated facsimile terminal. FIG.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 1/00 104 H04N 1/00 104B

Claims (3)

[Claims] A computer terminal accommodated in a computer network and a telephone network terminal accommodated in a telephone network are provided with an intermediate device (hereinafter simply referred to as a computer network) having an interface between the computer network and the telephone network. In the system for communicating a message via an intermediate device), communication of the message between the computer terminal and the intermediate device is performed in an encrypted manner, and communication of the message between the intermediate device and the telephone network terminal is not performed. An encrypted communication method characterized by performing encryption. 2. The intermediate device receives a message received from one of the computer terminal and the telephone network terminal.
2. The encrypted communication method according to claim 1, wherein the data is converted into a receivable medium of the other terminal. 3. When a message is sent from the computer terminal to another computer terminal having a different encryption method from the computer terminal, the message can be decrypted by the encryption method of the receiving computer terminal via the intermediate device. 2. The apparatus according to claim 1, wherein said message is re-encrypted by an intermediate device.
The encrypted communication method described.