JPH05122541A - Facsimile equipment with cipher communication function - Google Patents

Abstract

PURPOSE:To hold the privacy of image data even when transmitted data are wire-tapped from a telephone line by providing a ciphering circuit and a deciphering circuit at the facsimile equipment, transmitting the transmitting data in case of transmission after ciphering the data, and printing these data in case of reception after deciphering them. CONSTITUTION:When a communication key or a one-action dial key is turned on a control panel 10, a control part 1 reads the phone number of a communicating party stored in a RAM 2, and this number is transmitted through an automatic dialer 3 and an NCU 4 to a telephone line 5. Next, when received information is incoming through the line 5, NCU 4 and MODEM 7, the control part 1 records the information by driving a recording part 8. In this case, the control part 1 executes dial transmission and facsimile communication by using a non- standard frame in a transmission/reception processing and judges whether the opposite side equipment is provided with a cipher communication function or not. When the equipment is not provided with that function, a display part 11 executes display showing that the cipher communication is disabled and when the function is provided, random numbers are generated so as to disable deciphering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile machine having a cryptographic communication function.

[0002]

2. Description of the Related Art In facsimile communication, confidential communication has been conventionally performed as a method for realizing secret communication. In this confidential communication, for example, the transmission side delivers destination information together with the transmission image data to the address information, and the reception side temporarily stores the reception image data in the memory (that is, makes it secret), and Is a communication method in which the image data stored in the memory is read out and printed (that is, made visible) only when the password corresponding to the address information is input.

[0003]

However, in the above confidential communication, there is a drawback that the secret is easily leaked if the image data is tapped on the telephone line. SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a facsimile device with a cryptographic communication function that can protect the confidentiality of image data even if it is eavesdropped on a telephone line.

[0004]

In order to solve the above-mentioned problems, a facsimile apparatus with an encryption communication function according to the present invention, means for encrypting and transmitting transmission data, and means for decrypting received encrypted data. It is characterized by having and.

[0005]

According to the above configuration, even if the transmission data is wiretapped from the telephone line, the wiretap data is encrypted image data, so the confidentiality of the image data is kept unless it is decrypted. be able to.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. FIG. 1 is a block diagram showing a schematic circuit configuration of a facsimile apparatus,
In addition to controlling the entire facsimile, the facsimile apparatus uses a DH public key sharing system and has an encryption circuit 1a and a decryption circuit 1b to create encrypted data and decrypt encrypted data. RAM 2 for holding transmission data, reception data, telephone number, etc., auto dialer 3 for dialing, NCU 4 for controlling the line, and contents of a document set on a document table (not shown) optically. A reading unit 6 for reading, a modem 7 for performing modulation / demodulation processing, a recording unit 8 for recording on recording paper, and an RO for storing a program necessary for the operation of the control unit 1.
The M9, an operation panel 10 including a numeric keypad and a one-touch key, an encryption communication mode selection key, and the like, and a display unit 11 including an LCD are configured.

In such a facsimile machine, the basic transmission operation is roughly performed as follows. That is, when the operator turns on the communication key or the one-touch dial key on the operation panel 10, the controller 1 causes the R
The telephone number of the destination stored in the AM2 is read out, and the read telephone number is dialed to the telephone line 5 through the auto dialer 3 and the NCU 4. Then, after dialing, the image data of the original read by the reading unit 6 is sent to the telephone line 5 via the modem 7 and the NCU 4, and the sending operation is performed. On the other hand, the receiving operation is performed as follows. That is, when the reception information is received from the other party via the telephone line 5, the NCU 4, and the modem 7, the control unit 1 drives the recording unit 8 to record the reception information based on the reception information.

Further, the control section 1 can perform the following cipher communication processing by using a non-standard frame in the above-mentioned transmission / reception processing. When the encryption communication mode is selected by operating the encryption communication mode selection key, the processing on the transmitting side first executes dialing and facsimile communication procedures as shown in the flowchart of FIG. 2 (S1). In the procedure, a facsimile communication signal such as an NSF signal and a DIS signal (these signals are not encrypted) is received, and it is determined whether the partner machine has an encrypted communication function (S2). And
If the partner machine does not have the cryptographic communication function, the display unit 11 displays a message indicating that the cryptographic communication is disabled (S3), and the process ends. On the other hand, if the partner device has a cryptographic communication function, the built-in timer and PRG (Pseudo Ran)
and random number X _A are generated (S4).

Next, a public key Y _A (Y _A ≡g ^XA mod P: P is a prime number and g is a primitive element, both of which are shared information between transmission and reception) by a fast exponential calculation method using this X _A. Is calculated (S5), and this Y _A is transmitted (S6). on the other hand,
On the receiving side, the public key Y _B
Is calculated and is transmitted, this Y _B is received (S7), and the shared key K _AB (K _AB ≡Y is used using this Y _B.
B ^XA mod P) is calculated (S8).

Then, the processing such as training performed until the image data is actually transmitted is executed as usual (S9), and the CFR (procedure before the message is transmitted from the receiving side is completed and the message is transmitted). Whether or not there is a response signal indicating that the CFR can be started) is determined (S10), and if the CFR cannot be received within a predetermined time, the process ends.
If the CFR can be received, the encryption circuit 1a in the control unit 1 is activated (S11). Then, the data (plain text) M to be transmitted, that is, all of the image data (encoded image data) obtained by reading the original document by the reading unit 6 and the facsimile communication signals (EOL, EOM, MPS, etc.) are shared. Key K
Encrypted data in _AB and encrypted data C (C = E K _AB (M))
Then, the encrypted data C is transmitted (S12) (S1).
3). Of course, as a response to this data transmission, MCF (not encrypted) or the like is transmitted from the receiver side, and the communication is continued.

Then, it is judged whether or not the image data remains (S14), and if there is, the process proceeds to step 9, while if there is not, EOP is sent (S15) and the line is disconnected (S16). On the other hand, as the processing on the receiving side, as shown in the flow chart of FIG. 3, after the incoming call (S21), the facsimile communication procedure is executed (S22), and it is indicated that the partner machine has the cryptographic communication function by the NSF signal. Send. Then, like the transmitting side, a random number X _B is generated by the built-in timer and PRG (S23), and the public key Y _B (Y _B ≡g ^XB modP) is calculated by the fast exponential calculation method using this X _B. (S24), this public key Y _B is transmitted (S2
5). On the other hand, as described above, in the transmitting side, the public key Y _A in a similar manner is calculated, because it is transmitted, receives the Y _A (S26), the shared key K by using this Y _A
BA (K _BA ≡ Y _A ^XB modP) is calculated (S27).

Then, the processing such as training performed until the image data is actually transmitted is executed as usual (S28), and if the training is OK, the CFR is sent (S29). Decoding circuit 1b
Is activated (S30). Then, the encrypted data C (C =
E K _AB (M)) is received (S31), C is decrypted by the decryption circuit 1b into plain text M (M = D K _BA (C)) (S32),
A facsimile communication signal is detected from the decrypted plain text to perform communication, and the image data in the plain text is also decoded (decoding for run length coding) and printed in the recording unit 8, or An image data memory storage process for confidential reception is executed (S33).

Then, the presence or absence of EOP is judged (S3
4) If not, the process proceeds to step 31, while if there is, the process ends. According to the above configuration, even if the transmission data is tapped from the telephone line, the tapped data is the encrypted image data, so that the confidentiality of the image data can be protected unless it is decrypted. ..

In this embodiment, the encryption circuit 1a is activated when the CFR is received, and the decryption circuit 1b is activated when the CFR is transmitted to perform the encryption process. Although the timing of the shift is adjusted, it is also possible to shift to the encryption process immediately after obtaining the common key or when performing training.

Further, in the present embodiment, although the key shared by the DH public key distribution method is used to perform the communication by the secret key encryption,
This secret key cryptosystem includes cryptosystems such as involution ciphers represented by DES and stream ciphers (detailed in "Modern Cryptography" published by the Institute of Electronics and Communication Engineers), and any system may be used. Further, in the present embodiment, the encrypted transmission is performed only when the encrypted communication mode is selected. However, even when the encrypted communication mode is not selected, the receiver side has the encrypted communication function. If you know by handshake, you may automatically perform encrypted communication, and if you know that the receiver does not have an encrypted communication function, you may perform normal communication. is there.
In such a case, even if you should select the encrypted communication mode but forget it, if the other device has the encrypted communication function, the encrypted communication is automatically performed. Leakage of secrets due to eavesdropping can be avoided. FIG. 4 is a flowchart showing the above processing. First, it is judged whether or not the encrypted communication mode is selected (S41), and if it is selected, the flag F = 1 is set (S42), and the selected mode is selected. If not, the flag F = 0 is set (S43). Next, it is determined whether or not the partner machine has the cryptographic communication function (S44), and if it has the cryptographic communication function, the cryptographic communication is executed regardless of the state of the flag F (S45). On the other hand, if it does not have the encryption communication function, the state of the flag F is judged (S46), and the flag F = 1.
If so (in the encrypted communication mode), the encrypted communication impossible display is executed without communication (S48), and the flag F = 0.
If (normal mode), normal communication is executed (S
47).

[0016]

As described above, according to the present invention, even if the transmission data is eavesdropped from the telephone line, the eavesdropped data is encrypted image data, so long as it is not decrypted. The effect that the secret of the image data can be protected is achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a facsimile apparatus as an embodiment of the present invention.

FIG. 2 is a flowchart showing a transmitting side operation in a cryptographic communication mode.

FIG. 3 is a flowchart showing a receiving side operation for an encrypted communication request.

FIG. 4 is a flowchart on the transmitting side when the partner machine has a cryptographic communication function and cryptographic communication is performed regardless of whether the cryptographic communication mode is selected.

[Explanation of symbols]

 1 control unit 1a encryption circuit 1b decryption circuit

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Claims (1)

[Claims] 1. A facsimile apparatus with a cryptographic communication function, comprising: a means for encrypting and transmitting transmission data and a means for decrypting received encrypted data.