JPH1117960A - Cryptographic communication method for facsimile equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an enciphered sentence difficult to be deciphered by a third party by measuring the time interval of a predetermined operation such as an inputting interval of the facsimile number of a transmission destination, for example, based on transmitting operation performed by a user at the transmission side facsimile equipment and generating a cryptographic key based on the measured time interval. SOLUTION: Binary data outputted from a reading part 11 are encoded by an encoding part 15 and enciphered by a control part 1 while using a cryptographic key. When the FAX number of facsimile equipment on the opposite side is inputted from an operating part 13, the control part 1 samples the dialing interval of pressing the FAX number and generates a cryptographic key based on the sampled dialing interval. Thus, since the cryptographic key is frequency changed even without performing any special operation by a user, the enciphered sentence is made difficult to be deciphered by a third party and the cryptographic key can be generated without requiring any special hardware.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an encryption communication method for a facsimile machine.

[0002]

2. Description of the Related Art In a facsimile apparatus, a read image signal is converted into MH (Modified Hoffman) and MR (Modified Hoffman).
READ), and then transmitted. In a facsimile apparatus, it is conceivable that the encoded signal is further encrypted and transmitted in order to prevent the original signal from being decrypted from the transmission signal by a third party.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an encrypted communication method for a facsimile apparatus in which a ciphertext is difficult to be decrypted by a third party.

[0004]

According to a first aspect of the present invention, there is provided a facsimile communication method for a facsimile apparatus which performs encryption or decryption using an encryption key to perform encrypted communication. The transmission-side facsimile apparatus measures a predetermined operation time interval based on a transmission operation performed by a user, and generates an encryption key based on the measured time interval. The predetermined operation time interval is, for example, an input interval of a facsimile number of a transmission destination.

A second facsimile communication method for a facsimile apparatus according to the present invention is a facsimile communication method for a facsimile apparatus that performs encryption or decryption using an encryption key to perform encrypted communication. Measuring a time interval of a predetermined operation based on a transmission operation performed by the device, and generating an encryption key based on the measured time interval and a time interval of a predetermined number of times in the past. . The predetermined time interval of the operation is, for example, a time interval from when the one-touch dial button is pressed to when the start button is pressed.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a transmitting facsimile apparatus and a receiving facsimile apparatus.

[0008] The facsimile apparatus is controlled by a control unit 1 comprising a microcomputer or the like. The facsimile apparatus includes a reading unit 11, a recording unit 12, an operation unit 13, a display unit 14, an encoding unit 15, a decoding unit 16, a modem 17, and the like as input / output devices of the control unit 1. The modem 17 is connected to a public telephone line via a network control circuit (NCU) 18. The operation unit 13 includes various operation keys,
It has a numeric keypad and the like. The display unit 14 includes an operation unit 13
Is displayed.

At the time of transmission, the original image is
Read by 1 and binarized. The binarized image data output from the reading unit 11 is encoded by the encoding unit 15. The encoded data (plaintext) output from the encoding unit 15 is encrypted by the control unit 1. As this encryption method, a method of performing encryption using an encryption key is adopted.

The ciphertext created by the control unit 1 is modulated by the modem 17. And the network control circuit 18
Via the public telephone line and sent to the receiving facsimile machine.

At the time of reception, when the received data is sent to the network control circuit 18, the received data is demodulated by the modem 17. The data demodulated by the modem 17, that is, the ciphertext, is decrypted by the control unit 1 and returned to plaintext. As this decryption method, a method of performing decryption using an encryption key is adopted.

The plaintext obtained by the control unit 1 is decoded by the decoding unit 16. 2 obtained by decryption
The digitized image data is sent to the recording unit 12 and recorded on recording paper.

FIG. 2 shows the operation of the transmitting facsimile machine and the receiving facsimile machine.

First, in the transmitting facsimile machine,
Destination facsimile machine (receiving facsimile machine)
When the fax number is input, an interval at which the fax number is pressed (hereinafter referred to as a dialing interval) is sampled (step 1). Here, assuming that the destination fax number has seven digits, six dialing intervals T1 to T6 are sampled.

Next, an encryption key K is generated based on the six sampled dialing intervals T1 to T6 (step 2).

For example, assume that T1 to T6 have the following values. T1 = 0.246 seconds, T2 = 0.698 seconds, T3 =
1.005 seconds T4 = 0.365 seconds, T5 = 2.258 seconds, T6 =
1.026 seconds

The encryption key K is generated, for example, by sequentially arranging numbers below the decimal point of T1 to T5. That is, K = 246698005365258.

Next, a call is made to the destination facsimile machine (receiving facsimile machine) (step 3).

When the line is connected (step 21), the receiving facsimile apparatus receives an NSF (non-standard function identification signal).
Is transmitted (step 22). The NSF signal includes information such as whether or not the receiving facsimile apparatus has an encryption communication function or the like.

When the transmitting facsimile apparatus receives the NSF signal sent from the receiving facsimile apparatus (step 4), it reads the NSF signal (step 5). Then, it is determined whether or not the receiving-side facsimile apparatus has an encryption communication function, that is, whether or not encryption communication is possible (step 6). If the receiving-side facsimile apparatus does not have an encryption communication function, encryption communication is impossible, so that facsimile communication by normal communication is performed (step 13).

When the receiving-side facsimile apparatus has an encryption communication function, encryption communication is possible. Therefore, the transmission-side facsimile apparatus sets an encryption communication flag of an NSS signal (non-standard function setting signal) and sets ( Step 7), the encryption key K generated in Step 2 is set in the NSS signal (Step 8). Thereafter, an NSS signal and a TCF signal (training check signal) are transmitted (step 9). Further, the transmission-side facsimile apparatus generates a cipher text using the encryption key K generated in step 2 (step 10).

When the receiving facsimile apparatus receives the NSS signal and the TCF signal sent from the transmitting facsimile apparatus (step 23), it reads the NSS signal (step 24). Then, it is determined whether or not the communication is encrypted communication (step 25). If it is not encrypted communication,
Facsimile communication by normal communication is performed (step 32).

In the case of encrypted communication, the encryption key K is read from the NSS signal and stored (step 26). Further, the TCF signal is read (step 27), and the quality of the image is checked (step 28). Thereafter, a CFR signal (reception preparation confirmation signal) is transmitted (step 29).

When the transmitting facsimile apparatus receives the CFR signal (step 11), it starts transmitting the cipher text (step 12). That is, the ciphertext created by the control unit 1 is modulated by the modem 17, and then sent to the public telephone line via the network control circuit (NCU) 18,
Sent to the receiving facsimile machine.

In the receiving facsimile apparatus, when the ciphertext is sent to the network control circuit (NCU) 18 (step 3).
0), the received data is demodulated by the modem 17. The data demodulated by the modem 17, that is, the ciphertext, is decrypted by the control unit 1 and returned to the plaintext (step 31). That is, the ciphertext is plaintexted using the encryption key K read from the NSS signal in step 26.

When the transmitting facsimile apparatus has transmitted all the ciphertexts, it transmits an EOP signal (procedure end signal). Upon receiving the EOP signal, the receiving-side facsimile apparatus sends out an MCF signal (message confirmation signal).
When the transmitting facsimile apparatus receives the MCF signal,
A DCN signal (disconnection command signal) is transmitted. This allows
The communication ends.

In the above embodiment, the encryption key K is generated based on the dialing intervals T1 to T6. However, the time interval from when the one-touch dial button is pressed to when the start button is pressed (3 decimal places). (Digit value), the encryption key K may be generated.

Four buffers B1 to B4 for storing the last four operation intervals S1 to S4 are provided.
Here, S1, S2, S3,
S4. Then, it is assumed that the operation intervals S1 to S4 for the past four times are stored in the four buffers B1 to B4.

FIG. 3 shows an encryption key generation procedure performed by the transmission-side facsimile machine, which corresponds to the processing from step 1 to step 2 in FIG.

In the transmitting facsimile machine, after the facsimile number of the destination facsimile machine (receiving facsimile machine) is input by one-touch button,
When the start button is pressed, a time interval S0 from when the one-touch button is pressed to when the start button is pressed is measured (step 41).

Next, the past four time intervals S1, S2, S3 and S4 stored in the buffers B1 to B4 are read (step 42).

Then, based on a total of five time intervals S0 to S4 of the current time interval S0 obtained in step 41 and the past time intervals S1, S2, S3 and S4 read in step 42. , An encryption key K is generated (step 43).

It is assumed that the three digits after the decimal point of the time interval S0 and the time intervals (three digits after the decimal point) S1, S2, S3, and S4 stored in the buffers B1 to B4 have the following values. S0 = 698, S1 = 468, S2 = 943, S3 = 0
68, S4 = 642

The encryption key K is generated, for example, by sequentially arranging the numbers S0 to S4. That is, K = 69
84689430668642.

When the encryption key K is generated in this way,
The time interval S0 measured this time is stored in the first buffer B1, and the first to third buffers B1, B2, B3
Are stored in the second to fourth buffers B2 and B2.
3 and B4.

According to the above embodiment, even if the user does not perform any special operation, the encryption key K is frequently changed, so that it is difficult for a third party to decrypt the ciphertext. In addition, since it is not necessary to newly provide special hardware, the cost does not increase.

[0037]

According to the present invention, it is possible to realize an encrypted communication method for a facsimile apparatus in which a cipher text is difficult to be decrypted by a third party.

[Brief description of the drawings]

FIG. 1 is an electric block diagram showing a schematic configuration of a facsimile apparatus.

FIG. 2 is a flowchart illustrating operations of a transmitting facsimile machine and a receiving facsimile machine.

FIG. 3 is a flowchart illustrating another method for generating an encryption key.

[Explanation of symbols]

 1 control unit

Claims (4)

[Claims] An encryption communication method for a facsimile apparatus that performs encryption or decryption by using an encryption key to perform encryption communication, wherein the method is predetermined based on a transmission operation performed by a user in a transmission-side facsimile apparatus. A facsimile communication method for a facsimile apparatus, comprising: measuring a time interval between operations performed by the user; and generating an encryption key based on the measured time interval. 2. The encryption communication method for a facsimile apparatus according to claim 1, wherein the predetermined operation time interval is an input interval of a facsimile number of a transmission destination. 3. A facsimile communication method for a facsimile apparatus that performs encryption or decryption by using an encryption key to perform encrypted communication, wherein the method is predetermined based on a transmission operation performed by a user in a transmission-side facsimile apparatus. A time interval of the operation performed by the user, and generating an encryption key based on the measured time interval and a predetermined time interval in the past. 4. The encryption communication method for a facsimile apparatus according to claim 3, wherein the predetermined time interval of the operation is a time interval from when the one-touch dial button is pressed to when the start button is pressed.