JPH07154613A - Ciphering communication method and terminal equipment for ciphering communication - Google Patents

Abstract

PURPOSE:To execute ciphering communication by the same processing time as that of usual communication and to simplify the configuration of the entire equipment by implementing ciphering/decoding processing simultaneously in the case of coding/decoding processing. CONSTITUTION:A coding section 17 encodes picture information corresponding to an original based on a ciphering code table in which a cross reference of a standard code table is rearranged at random. The code obtained by cod processing is sent to a telephone line. Furthermore, the information representing whether or not the mode is the ciphering communication mode is sent to the telephone line prior to the transmission of codes. When the ciphering communication mode is selected, a control section 3 of a receiver side facsimile equipment applies decod processing according to the same rule as that of the ciphering code table to the received code. Thus, the received code is reproduced into an original picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryptographic communication method applied when performing cryptographic communication between a calling side terminal device and a called side terminal device, and a terminal device for implementing the method. Is.

[0002]

2. Description of the Related Art In the field of communication, communication data may be encrypted in order to keep the communication data confidential. For example, even in facsimile communication in which image information corresponding to a document is transmitted and received, the image information may be encrypted in order to prevent the image information from leaking.

In the encryption processing conventionally performed in facsimile communication, image information is encrypted using a so-called encryption key. Specifically, a predetermined logical operation using an encryption key is performed on the image information to create encrypted information that is completely different from the original image information. On the other hand, the decryption process for restoring the encrypted information to the original image information is achieved by subjecting the encrypted information to a predetermined logical operation using the encryption key. The logical operation for decryption processing is the opposite operation to the logical operation for encryption processing.

[0004]

In the above encryption processing, a complicated algorithm is used in order to increase the encryption strength (degree of encryption). Therefore, there is a problem in that the encryption process takes a long time, dedicated hardware equipment is required, and the configuration of the entire facsimile apparatus becomes complicated.

Therefore, an object of the present invention is to solve the above technical problems, to provide a cryptographic communication method capable of shortening the processing time and simplifying the configuration of a terminal device. Another object of the present invention is to provide a terminal device for implementing the encrypted communication method.

[0006]

According to a first aspect of the present invention, there is provided a cryptographic communication method, wherein information is encoded from a calling side terminal device to a called side terminal device through a predetermined communication line. Is a cryptographic communication method applied to a communication system for transmitting, the calling terminal device creates encrypted information by performing an encoding process on the information to be transmitted under a rule different from a normal rule, The created encrypted information is sent to the predetermined communication line, and the called terminal device changes the encrypted information received from the calling terminal device via the predetermined communication line to the calling terminal device. It is characterized in that the encrypted information is decrypted by performing the decryption processing according to the same rule as in the above.

A terminal device according to a second aspect is a terminal device for transmitting encoded information to a called side terminal device connected via a predetermined communication line, and the information to be transmitted. And a means for creating encrypted information by performing an encoding process according to a rule different from the normal rule, and a means for sending the created encrypted information to the predetermined communication line. .

Further, the terminal device according to claim 3 connects the encrypted information created by performing the encoding process on the information to be transmitted according to a rule different from the normal rule, via a predetermined communication line. And a means for receiving the encrypted information from the calling side terminal device via the predetermined communication line, and a received terminal device for receiving the encrypted information. Means for decrypting the encrypted information by performing a decryption process according to the same rule as that of the calling terminal device.

[0009]

In the above structure, the calling side terminal device creates the encrypted information by performing the encoding process on the information to be transmitted according to the rule different from the normal rule, and sends the encrypted information to the predetermined communication line. It On the other hand, in the called terminal device, the encrypted information received via the communication line is decrypted by performing the decryption process according to the same rule as the calling terminal device. A terminal device that does not know the encoding rule at the time of encryption cannot decrypt the encrypted information even if it receives the encrypted information, so the communication content is kept confidential.

As described above, even when the encrypted communication is executed, the calling side terminal device only performs the encoding process and the called side terminal device only performs the decoding process. Therefore, the processing by complicated algorithm is unnecessary,
It does not require long processing time. Further, since encrypted communication can be executed by any device that can perform encoding or decoding processing, a hardware device dedicated to encrypted communication is unnecessary.

[0011]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electrical configuration of a facsimile apparatus to which the first embodiment of the present invention is applied. This facsimile apparatus has a control unit 3 connected to a telephone line via a modem 1, an original reading unit 5 for reading an original to be transmitted, and a recording for recording an image received via the telephone line. And part 7. The control unit 3 includes an operation panel 9 for inputting a facsimile number, a RAM (random access memory)
The image information storage unit 11 and the motor drive circuit 10 for driving the motor 8 as a drive source of the document reading unit 5 and the recording unit 7 are connected.

The original reading section 5 includes an image sensor 51 for reading an optical image of the original 15 and converting it into an electric signal.
The image sensor 51 is provided with a lens 52 for forming an optical image of a document. The image sensor 51 is
The document is electrically scanned along a predetermined main scanning direction. The document is conveyed in the sub-scanning direction that intersects the main scanning direction, whereby the sub-scanning is achieved. The output signal of the image sensor 51 is converted into image information composed of binary data in the image processing circuit 53. This image information is input to the control unit 3 after being subjected to compression encoding processing in the encoding unit 17. The control unit 3 stores the code from the encoding unit 17 in the image information storage unit 11. The codes stored in the image information storage unit 11 are sequentially read and sent from the modem 1 to the telephone line. The compression encoding process in the encoding unit 17 is
This is executed by referring to the encoding / decoding reference table 21 that stores a code table representing the correspondence between the characteristics of image information and codes.

When a code is received from the telephone line via the modem 1, the received code is input to the decoding unit 19. The decoding unit 19 refers to the encoding / decoding reference table 21 to restore the received code into image information. The restored image information is given to the control unit 3 and stored in the image information storage unit 11. The image information stored in the image information storage unit 11 is read by the control unit 3 and given to the recording unit 7.

The recording section 7 has an image recording unit 71 for recording an image on the recording paper 25. For example, when thermal paper is used as the recording paper 25,
The image recording unit 71 is composed of a thermal head. As the image recording unit 71, a unit that forms an image according to, for example, an electrophotographic process may be applied. Reference numeral 72 is a recording processing circuit that generates a drive signal for the image recording unit 71 based on image information.

The operation panel 9 is provided with an operation section 91 having a ten-key pad, a mode setting key, etc., and a display section 92. The mode setting key is a key for setting a plurality of operation modes of the facsimile device. The operation modes include, for example, a normal mode for performing normal communication and a cryptographic communication mode for performing cryptographic communication. The display unit 92 is composed of, for example, a liquid crystal panel, and is used to display a facsimile number of a communication destination and other messages.

In the present embodiment, when the normal mode is selected, the encoding unit 17 and the decoding unit 19
MH (Modified Huffman) method, MR (Modified READ)
, READ: Relative Element Address Designate) or MMR (Modified MR). Therefore, next, these encoding methods will be outlined.

The MH system is a one-dimensional coding system. That is, the black run length and the white run length on one scanning line when the document is scanned are detected as local features of the image information, and they are shown in Table 1 and the terminating codes shown in Table 2 and Table 3. It is encoded by the makeup code shown. Run lengths in the range 0-63 pixels are coded with terminating codes only. The run length of 64 to 1791 pixels is a makeup code indicating a run length equal to or less than the run length,
It is expressed by combining the run length represented by the makeup code and the terminating code corresponding to the difference between the actual run length. For run lengths of 1792 pixels or more, the makeup code shown in Table 3 below the run length and the makeup of Table 2 representing the run length less than the difference between the run length represented by the makeup code and the actual run length are shown. It is expressed by combining an up code and a terminating code corresponding to the difference between the sum of the run lengths represented by these two makeup codes and the actual run length. Each scan line must always start with a white run length, and for lines starting with a black run length, a white run length code of length 0 is created first.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

The MR encoding system is a two-dimensional encoding system, which is a combination of one-dimensional encoding and two-dimensional encoding utilizing the correlation between adjacent scanning lines. That is, when a certain line is one-dimensionally encoded, two-dimensional encoding is performed on the (K-1) line (where K is a parameter) following the line. The one-dimensional encoding is performed in exactly the same manner as the MH method.

Two-dimensional encoding will be described with reference to FIG. In the two-dimensional encoding, when encoding the encoding line LE, the reference line LR immediately before the encoding line LE is referred to.
At this time, the pixels a ₀ , a ₁ , a ₂ , b ₁ , b ₂ at the change points between the black pixels and the white pixels on the reference line LR and the encoding line LE are defined as follows. a ₀ : Encoding origin pixel a ₁ : First change pixel on the encoding line to the right of a ₀ a ₂ : First change pixel on the encoding line to the right of a ₁ b ₁ : On the reference line there, the first change pixel b ₂ having the color information of the opposite a ₀ on the right than a _0: first change pixel encoding procedure of the b ₁ on the reference line right, the next [step 1], It is executed according to [Procedure 2] and [Procedure 3]. At this time, the two-dimensional coding table shown in Table 4 below is used.

[0023]

[Table 4]

[Procedure 1] When b ₂ exists on the left side of a ₁ , it is set to the pass mode (symbol P). At this time, the code “0001” corresponding to the pass mode is generated. After that, the pixel immediately below b ₂ becomes a new starting pixel a ₀ .
If it is not the pass mode, proceed to [Procedure 2].

[Procedure 2] First, the absolute value | a ₁ b ₁ | of the relative distance between the changed pixels a ₁ and b ₁ is obtained. | A
_{If 1} b ₁ | ≦ 3, it is detected as the vertical mode (symbol V), and a code corresponding to the distance between a ₁ and b ₁ is generated according to the two-dimensional code table of Table 4. After that, the pixel a ₁ becomes a new starting pixel a ₀ . In Table 4, subscripts R and L attached to the symbol V indicate that a ₁ is on the right side and the left side with respect to b ₁ , and the numbers in parentheses indicate the distance between a ₁ and b ₁ . Represents an absolute value. That is, for example, the symbol V
_{In R} (2), the change pixel a ₁ is the change pixel b of the reference line LR.
Indicates that it is on the right side by 2 pixels from ₁ .

│a₁b₁If |> 3, [procedure
3]. [Procedure 3] | a₁b₁Horizontal mode when |> 3
(Symbol H) is detected. And in horizontal mode
"A" following the code "001" indicating that₀a₁and
a ₁a₂One-dimensional code of each run length
Issue is generated. After this, pixel a₂Is a new starting pixel a
₀Becomes

An example of encoding according to the procedure as described above is shown in FIG.
Shown in. The MMR system is an improvement of the above-mentioned MR system, and the basic method of two-dimensional encoding is the same as the MR system. By the way, the MH system, the MR system and the MMR system described above are recommended by the T.T. It is a standardized method in 30. Therefore, the one-dimensional code table and the two-dimensional code table shown in Tables 1 to 4 are also standardized. Therefore, in a normal facsimile apparatus, the encoding / decoding process is executed by using this standardized code table. Therefore, the facsimile apparatus on the receiving side can always reproduce the original image because the decoding can be performed according to the same rule as the encoding rule on the facsimile apparatus on the transmitting side. on the other hand,
When the facsimile machine on the transmission side executes the encoding process using a code table different from the above code table, the facsimile machine on the reception side cannot reproduce the original image.

Therefore, in this embodiment, paying attention to this point,
When the cipher communication mode is selected, the correspondence relationship in the code table is randomly rearranged to execute the coding process. That is, the encoding process is executed according to the encryption code table in which the correspondence relationship between the run length and the code or the correspondence relationship between the mode and the code is randomly rearranged.
In this embodiment, the allocation of modes and codes in two-dimensional encoding is recombined. This mode allocation recombination is realized by the function of the control unit 3.

FIG. 4 is a diagram for explaining rearrangement of allocation of modes and codes. In the encoding / decoding reference table 21, as shown in FIG. 4 (a), for example, P in the area of address 1000H (H at the end indicates that the number before it is hexadecimal) to 18FFH. H, V (0)
_{, V R (1), V} R (2), V R (3), V L (1), V L (2)
And codes corresponding to V _L (3) are stored.

When normal transmission is performed, the encoding unit 1
Under the control of the control unit 3, the reference numeral 7 sets the correspondence relationship between each mode and the address of the coding / decoding reference table 21 to the correspondence relationship shown in FIG. on the other hand,
When performing encrypted communication, the encoding unit 17 sets the correspondence relationship between each mode and the address of the encoding / decoding reference table 21 to the correspondence relationship shown in FIG. 4C under the control of the control unit 3. Then, the two-dimensional encoding process is performed. The code created in this way cannot be reproduced as an original image by a normal decoding process.

FIG. 5 is a flow chart for explaining the operation on the transmission side in encrypted communication. The operator sets the original to be transmitted on the original reading unit 15 and
Operate the operation unit 91 to perform a necessary operation (step S
1). That is, the setting of the number of the destination facsimile machine, the setting of the transmission mode (normal mode or encrypted communication mode), and the key input operation for starting the transmission are performed.

In response to such an operation, the optical reading of the original is started (step S2). Image information represented by binary data is output from the image processing circuit 53 to which the output signal of the document reading unit 15 is input. The encoding unit 17 determines whether the encryption communication mode is set (step S3),
The image information is encoded according to either the first operation or the second operation. More specifically, when the mode is not the cipher communication mode, the correspondence relationship of the code table is set to the normal relationship shown in FIG.
Encoding processing is performed according to the operation (step S4). On the other hand, in the encrypted communication mode, the coding process is performed according to the second operation of setting the correspondence of the code table to the randomly rearranged relation of FIG. 4 (c) and executing the coding process (step S5).

The code obtained by such an encoding process is once stored in the image information storage section 11 and sent from the control section 3 through the modem 1 to the telephone line as a modulated signal (step S6). Prior to transmitting the code, the control unit 3 transmits information indicating whether or not the encryption communication mode is selected to the facsimile apparatus on the receiving side.

The operation of the facsimile machine on the receiving side is as follows. That is, following the line connection,
The control unit 3 of the facsimile apparatus on the receiving side refers to the information indicating whether or not the communication mode is the encrypted communication mode transmitted from the facsimile apparatus on the transmitting side, and controls the decryption operation in the decrypting unit 19 accordingly. As a result, the decoding process is performed assuming that the relationship between the mode and the code in the two-dimensional encoding process is set to the relationship of FIG. 4 (c) when in the encrypted communication mode and to the relationship of FIG. 4 (b) otherwise. Run.
That is, the decoding unit 19 decodes the received code into image information according to the same rule as the coding rule in the facsimile apparatus on the transmission side. The image information decoded in this way is temporarily stored in the image information storage unit 11. After that, the control unit 3
The received image is recorded in the recording unit 7 based on the control by.

As described above, according to the present embodiment, when performing the encrypted communication, the encoding / decoding process is performed based on the code table for the encrypted communication in which the correspondence between the mode and the code is randomly rearranged. To be executed. Therefore, as compared with the conventional technique using the encryption key, the algorithm for executing the encrypted communication can be remarkably simplified. Therefore, encrypted communication can be executed in almost the same processing time as normal communication.

Further, since special hardware equipment for encrypted communication is not required and the encrypted communication can be executed by using the encoding unit 17 and the decoding unit 19 provided in a normal facsimile apparatus, the facsimile can be executed. The configuration of the entire device can be simplified. In the above embodiment, the correspondence between modes and codes is randomly rearranged, but in this case,
It is preferable to rearrange so that the amount of codes to be transmitted does not become too large.

Further, for example, the correspondence between modes and codes may be recombined for encrypted communication according to a rule that maximizes the transmission efficiency of halftone images. further,
In the above embodiment, the code table recombination in the two-dimensional encoding has been described, but the code table recombination in the one-dimensional encoding may be performed. That is, for example, only the code assigned to the white run length may be used. This is because the white run length and the black run length always appear alternately, so that the distinction between the white run length and the black run length is not necessarily important.

Furthermore, in the one-dimensional encoding, when the run length is 1, 2, 3 or 4, the code assigned to the black run length is used, and the white run length is used for the other run lengths. Good. Furthermore, the recombination of code tables in the one-dimensional encoding and the recombination of code tables in the two-dimensional encoding may be used together.

FIG. 6 is a diagram for explaining the second embodiment of the present invention. In the description of this embodiment, FIG. 1 described above will be referred to again. In the present embodiment, when performing cipher communication, when the encoding unit 17 encodes image information for one line of the document input from the document reading unit 5, an illegal code is inserted at the beginning of the code for one line. To be done. The illegal code is a code that is not used in ordinary facsimile communication.

In normal communication, as shown in FIG. 6 (a),
The encoding unit 17 of the transmission side facsimile device inserts an EOL (End Of Line) code indicating a line delimiter at the head of the code corresponding to the image information for one line. When the facsimile machine on the receiving side receives the code from the telephone line,
The EOL code is detected from among them to recognize line breaks. On the other hand, as shown in FIG. 6B, if the sending facsimile machine inserts an illegal code instead of the EOL code, the receiving facsimile machine cannot recognize the line break. for that reason,
The receiving facsimile machine cannot reproduce the original image.

FIG. 7 is a flow chart showing the operation on the transmitting side of this embodiment. When the operator sets a document to be transmitted on the document reading unit 15 and performs a necessary operation (step N1), the reading of the document is started (step N2).
In this case, if the encrypted communication mode is selected (step N3), the encoding unit 17 inserts an illegal code at the beginning of the code corresponding to the image information for one line (step N4). On the other hand, if the mode is not the encrypted communication mode, a normal EOL code is inserted (step N5).

The generated code is temporarily stored in the image information storage section 11 and then transmitted from the control section 3 through the modem 1 to the facsimile machine on the receiving side (step N6). Prior to starting the transmission of the code, the control unit 3 transmits the information indicating that the encrypted communication mode is set to the facsimile apparatus on the receiving side via the telephone line. When the encrypted communication mode is set, the receiving facsimile machine determines that the illegal code is inserted instead of the EOL code, recognizes the line delimiter based on the illegal code, and detects the original image. To restore.

It should be noted that the original image is not reproduced in the facsimile machine which does not know the encryption rule that the illegal code is used instead of the EOL code.
Thus, in this embodiment, the EOL that is normally inserted is
The encrypted communication can be performed simply by inserting the illegal code instead of the code, so the algorithm for executing the encrypted communication can be significantly simplified, and no special hardware device for executing the encrypted communication is required. .

FIG. 8 is a block diagram showing the electrical construction of a facsimile apparatus to which the third embodiment of the present invention is applied. In FIG. 8, parts having the same functions as those of the parts shown in FIG. 1 are designated by the same reference numerals. In the present embodiment, when performing encrypted communication, the document reading unit 5
The image information output from is stored in the line memory 30, and after the image information for one line is stored, the encoding process of the image information for one line is executed in the reverse order of the stored order. It That is, the image information is encoded from the back of the line.

In normal communication, when the facsimile device on the transmission side executes the encoding process on the image information for one line, the facsimile device on the transmission side executes the encoding process in order from the beginning of the line and transmits it to the facsimile device on the receiving side. . Therefore, the facsimile machine on the receiving side can reproduce the original image by executing the decoding process in the order of reception. On the other hand, if the order in which the encoding process is performed in the sending side facsimile device is reversed, the receiving side facsimile device that does not know such an encoding rule executes the decoding process in the receiving order. However, the original image cannot be reproduced.

FIG. 9 is a flow chart for explaining the operation on the transmitting side. When the operator sets a document to be transmitted on the document reading unit 15 and performs a necessary operation (step P1), the reading of the document is started (step P2).
In this case, if the encryption communication mode is selected (step P3), the encoding unit 17 sequentially stores the image information input from the document reading unit 15 in the line memory 30 (step P4). When the image information for one line is stored, the image information is read out in the reverse order of the storage and the encoding process is executed (step P5). On the other hand, if the mode is other than the encrypted communication mode, normal encoding processing is executed (step P6).

The generated code is temporarily stored in the image information storage section 11 and then transmitted from the control section 3 through the modem 1 to the facsimile machine on the receiving side (step P7). Prior to starting the transmission of the code, the control unit 3 transmits the information indicating that the encrypted communication mode is set to the facsimile apparatus on the receiving side via the telephone line. When the encrypted communication mode is set, the receiving facsimile machine recognizes that the received code is encoded from the back of the line, and performs decoding processing on the received code from the back of the line. The original image is reproduced by applying it.

As described above, in this embodiment, since the encrypted communication is achieved by encoding the image information from the back of the line, the algorithm for executing the encrypted communication can be remarkably simplified and the encrypted communication can be performed. You don't need any special hardware equipment for. FIG. 10 shows the fourth embodiment of the present invention.
1 is a block diagram showing an electrical configuration of a facsimile apparatus to which an embodiment is applied. In FIG. 10, in FIG.
The parts having the same functions as the parts shown in FIG. In this embodiment, when performing encrypted communication, the image information output from the document reading unit 5 is stored in the page memory 40, and after one page of image information is stored, n (for example, n = 4) is stored. The encoding process is executed every line.

FIG. 11 is a diagram for explaining the encoding process in the encoding unit 17 in more detail. The encoding unit 17
When the image information for one page is stored in the page memory 40, the image information of the 1st, n + 1, 2n + 1, ..., kn + 1 (where k is a natural number) line is first encoded. Then, 2, n + 2,2n + 2, ..., kn +
The image information of the second line is encoded in order. Similarly, n-1, n + (n-1), 2n + (n-1), ...
Encoding up to the image information of the kn + (n-1) th line. As a result, the encoding of the image information for one page is achieved.

In normal communication, image information is encoded line by line from the top and transmitted to the facsimile machine on the receiving side. The receiving-side facsimile apparatus can reproduce the original image by performing the decoding processing in the order of reception.
However, if the transmitting facsimile machine encodes the image information every n lines, the receiving facsimile machine that does not know such an encoding rule will perform the decoding process in the order in which the original image is received. Can't play.

FIG. 12 is a flow chart for explaining the operation on the transmitting side. When the operator sets a document to be transmitted on the document reading section 15 and performs a necessary operation (step T1), the reading of the document is started (step T).
2). In this case, if the encryption communication mode is selected (step T3), the encoding unit 17 sequentially stores the image information input from the document reading unit 15 in the page memory 40 (step T4). When the image information for one page is stored, the image information is read every n lines and the encoding process is executed (step T5). On the other hand, if the mode is other than the encrypted communication mode, a normal encoding process for sequentially encoding each line is executed (step T6).

The generated code is temporarily stored in the image information storage section 11 and then transmitted from the control section 3 through the modem 1 to the facsimile machine on the receiving side (step T7). Prior to starting the transmission of the code, the control unit 3 transmits the information indicating that the encrypted communication mode is set to the facsimile apparatus on the receiving side via the telephone line. When the encrypted communication mode is set, the facsimile machine on the receiving side recognizes that the received code is encoded every n lines and decodes the received image information every n lines. The original image is reproduced by applying.

As described above, in this embodiment, since the encrypted communication is achieved by encoding the image information for one page every n lines, the algorithm for executing the encrypted communication can be remarkably simplified. In addition, no special hardware device is required for encrypted communication. Figure 13
It is a figure for demonstrating the 5th Example of this invention. In addition,
In the description of this embodiment, FIG. 1 described above will be referred to again. In the present embodiment, in the case of performing encrypted communication, after the code encoded by the normal encoding process is stored in the image information storage unit 11, the control unit 3 transmits the code for each one byte to the image information storage unit 11. The code for one byte read out is transmitted from the least significant bit (LSB: Least Significant Bit) to the most significant bit (MSB: Most Significant Bit) on the telephone line. In this example,
The process of changing the transmission order of the codes from the LSB to the MSB by the control unit 3 is called an encoding process.

In normal communication, the facsimile machine on the transmitting side, as shown in FIG.
In the order of going to B, 1-byte image information is sent to the telephone line. On the other hand, the facsimile machine on the receiving side executes the decoding process in the order of reception to reproduce the original image. If the sending facsimile machine sends out codes in the order from the LSB to the MSB as shown in FIG. 13 (b), the receiving facsimile machine not knowing such a rule reproduces the original image. I can't.

FIG. 14 is a flow chart for explaining the operation on the transmitting side. When the operator sets a document to be transmitted on the document reading unit 15 and performs a necessary operation (step U1), the reading of the document is started (step U).
2). The image information corresponding to the document is encoded by the encoding unit 17 and then temporarily stored in the image information storage unit 11 (step U3). The code stored in the image information storage unit 11 is sequentially read by the control unit 3 byte by byte and sent to the telephone line. At this time, in the processing in step U1 above,
If the encrypted communication mode is selected (step U
4), the control unit 3 sets the read 1-byte code to the LSB.
To the telephone line in order (step U5). on the other hand,
In the modes other than the encrypted communication mode, the MSBs are sequentially transmitted to the telephone line as usual (step U6).

Prior to starting the transmission of the code, the control unit 3 transmits information indicating that the encrypted communication mode is set to the facsimile apparatus on the receiving side via the telephone line. When the encryption communication mode is set, the facsimile machine on the receiving side recognizes that the received code is transmitted from the LSB and recognizes the 1-byte code as the image information storage unit 1.
After being stored in 1, the image information is restored by sequentially reading from the LSB and performing a decoding process.

As described above, in this embodiment, the encrypted communication is achieved by transmitting the code for 1 byte from the LSB, so that the algorithm for executing the encrypted communication can be remarkably simplified and the encrypted communication can be performed. There is no need for special hardware equipment for FIG. 15 is a diagram for explaining the sixth embodiment of the present invention. The description of this embodiment will be made again with reference to FIG. In the present embodiment, when encrypted communication is performed, after the code encoded by the normal encoding process is temporarily stored in the image information storage unit 11,
The control unit 3 reads out codes for m (for example, m = 4) bytes from the image information storage unit 11, exchanges the order of the read codes for m bytes, and sends them to the telephone line. This replacement is performed, for example, according to a predetermined method or password. The unit of the read code may be a word. Further, in the present embodiment, the process until the transmission order of the codes is changed by the control unit 3 is called an encoding process.

In normal communication, the control unit 3 of the facsimile apparatus on the transmission side sequentially reads out the codes from the image information storage unit 11 and sends them to the telephone line in the order of reading out, as shown in FIG. 15 (a). Since the facsimile machine on the receiving side performs the decoding process in the order of reception, it can reproduce the original image. However, as shown in FIG. 15 (b), if the sending side facsimile apparatus exchanges m bytes of codes and sends them, the receiving side facsimile apparatus that does not know such a rule receives Even if the decoding process is executed in the specified order, the original image cannot be reproduced.

FIG. 16 is a flow chart for explaining the operation on the transmitting side. When the operator sets a document to be transmitted on the document reading section 15 and performs a necessary operation (step V1), the reading of the document is started (step V).
2). The image information corresponding to the original is encoded by the encoding unit 17 and then temporarily stored in the image information storage unit 11 (step V3). The code stored in the image information storage unit 11 is sequentially read byte by byte and sent to the telephone line. At this time, if the encrypted communication mode is selected in the process in step V1 (step V4), the control unit 3 reads the m bytes of code and switches the order of the m bytes of code. And sends it to the telephone line (step V5). On the other hand, in the modes other than the encrypted communication mode, the codes are sent to the telephone line in the order of reading as usual (step V6).

Prior to starting the transmission of the code, the control section 3 transmits the information indicating that the encrypted communication mode is set to the facsimile apparatus on the receiving side via the telephone line. When the encryption communication mode is set, the facsimile apparatus on the receiving side restores the image information on the assumption that the order of m bytes of the received code is exchanged with each other and transmitted.

As described above, in the present embodiment, the encrypted communication is achieved by transmitting the m-byte image information with the order thereof exchanged with each other, and the algorithm for executing the encrypted communication is remarkably simple. In addition, it does not require special hardware equipment for encrypted communication. The present invention has been described above, but the present invention is not limited to the above embodiments. For example, in the above-described embodiment, a technique of sequentially encoding image information for one line from the back (third embodiment) and a technique of encoding image information for one page every n lines (fourth embodiment). Are described separately, but each of these techniques may be combined, for example. Further, it is also possible to further combine the technology (sixth embodiment) in which the order of codes for m bytes is exchanged with each other and transmitted to the telephone line. Furthermore, any number of other combinable technologies may be combined.

Further, in the above embodiment, the MH system, the MR system and the MMR system were described as the coding system, but the present invention can be applied to other coding systems. Further, in the above-described embodiment, the facsimile device is described as an example of the terminal device, but the present invention can be applied to other terminal devices such as a personal computer and a word processor, and various other terminal devices capable of encrypted communication. Can also be widely applied.

Furthermore, in the above-mentioned embodiment, the image information is explained as an example of the information to be transmitted, but the present invention can be applied when transmitting information other than the image information. Other various design changes can be made without changing the gist of the present invention.

[0064]

As described above, according to the present invention, coding /
Since the encryption / decryption process can be performed at the same time as the decryption process, the algorithm for encrypted communication can be significantly simplified. Therefore, the encrypted communication can be executed in almost the same processing time as the normal communication. In addition, since a configuration for encoding / decoding processing can be used, a dedicated hardware device is not required to execute encrypted communication. Therefore, the configuration of the entire terminal device can be simplified as compared with the related art.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a facsimile apparatus to which a first embodiment of the present invention is applied.

FIG. 2 is a diagram for explaining a two-dimensional encoding process.

FIG. 3 is a diagram showing an example of two-dimensional encoding.

[Fig. 4] Fig. 4 is a diagram for explaining a change in allocation of modes and codes in two-dimensional encoding.

FIG. 5 is a flowchart showing an operation on the transmitting side.

FIG. 6 is a diagram for explaining a second embodiment of the present invention.

FIG. 7 is a flowchart showing an operation on the transmitting side in the second embodiment.

FIG. 8 is a block diagram showing an electrical configuration of a facsimile apparatus to which a third embodiment of the present invention has been applied.

FIG. 9 is a flowchart showing an operation on the transmitting side in the third embodiment.

FIG. 10 is a block diagram showing an electrical configuration of a facsimile apparatus to which a fourth embodiment of the present invention has been applied.

FIG. 11 is a diagram for explaining the fourth embodiment in more detail.

FIG. 12 is a flowchart showing an operation on the transmitting side in the fourth embodiment.

FIG. 13 is a diagram for explaining the fifth embodiment of the present invention.

FIG. 14 is a flowchart showing an operation on the transmitting side in the fifth embodiment.

FIG. 15 is a diagram for explaining the sixth embodiment of the present invention.

FIG. 16 is a flowchart showing an operation on the transmitting side in the sixth embodiment.

[Explanation of symbols]

 3 Control Unit 17 Encoding Unit 19 Decoding Unit 21 Encoding / Decoding Reference Table

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Mori 1-22 Tamagaku, Chuo-ku, Osaka-shi, Osaka Mita Industry Co., Ltd.

Claims (3)

[Claims] 1. A cryptographic communication method applied to a communication system for transmitting coded information from a calling side terminal device to a called side terminal device via a predetermined communication line, the calling side terminal device comprising: Creates encrypted information by performing encoding processing on the information to be transmitted according to a rule different from the normal rule, sends the created encrypted information to the predetermined communication line, and the called terminal device Decrypts the encrypted information by subjecting the encrypted information received from the calling terminal device via the predetermined communication line to a decryption process in accordance with the same rule as the rule in the calling terminal device. A cryptographic communication method characterized by the above. 2. A terminal device for transmitting coded information to a called terminal device connected via a predetermined communication line, wherein the information to be transmitted has a rule different from a normal rule. A terminal device comprising: means for creating encrypted information by performing an encoding process; and means for sending the created encrypted information to the predetermined communication line. 3. Received from a calling terminal device connected via a predetermined communication line, encrypted information created by encoding information to be transmitted according to a rule different from a normal rule. And a means for receiving the encrypted information from the calling side terminal device via the predetermined communication line, and a rule in the calling side terminal device for the received encrypted information. A terminal device, comprising means for decrypting the encrypted information by performing decryption processing according to the same rule.