JPH09154007A - Secret information recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect the secrecy of recorded information by embedding dot data obtained from binary secret information data in public information data made into dots from cipher key information and preparing printing data according to the synthetic information. SOLUTION: In the dot making processing 5 of public information pictures, the pictures of public information are converted to the public information data made into the dots. In the binarization processing 1 of secret information, the required secret information is converted to the binary secret information data and the dot data for recording the secret information are obtained, based on the data. Then, data relating to the embedding position information and embedding method of the dot data in a printing medium are prepared as the cipher key information. In a secret information data embedding processing 8, the dot data are embedded in the public information data made into the dots from the cipher key information and the synthetic information is obtained. In a printing processing 9, the printing data are prepared according to the synthetic information data and the pictures are printed on the printing medium according to the printing data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records confidential information on a print medium such as a sheet of paper in accordance with the information of an encryption key so that a third party does not know the existence of the confidential information, and restores the encryption key in pairs. The present invention relates to a confidential information recording method that allows only a person who has a key to reproduce it if necessary.

[0002]

2. Description of the Related Art As a method of hiding and recording confidential information on a paper surface, a method of printing required confidential information on a paper surface with a special transparent paint is known. However, this method makes it difficult to manufacture a special ink, resulting in high cost, and its chemical properties deteriorate with the passage of time, resulting in poor storage stability, making it impossible to copy using a copying machine. It has a problem that it cannot meet the demand for a large number of copies.

As a solution to these drawbacks, the dots (pixels) forming the characters and numbers printed on the paper surface.
, The confidential information code is embedded by shifting the specific position of the scanning line (Japanese Patent Laid-Open No. 60-48586), or the number of pixels of the scanning line in the facsimile transmission document is changed according to a predetermined rule. Embedded in the facsimile image data, and the document in which the signature text is embedded in this way is scrambled and transmitted (JP-A-5-3779).
No. 5) is known.

[0004]

However, these known methods change the position of the pixel of the public information to be printed on the print medium such as a paper surface or change the number of pixels of the scanning line. Therefore, in any case, the amount of information that can be embedded depends on the state of the image in which the confidential information is embedded, and there is a problem in that a large amount of confidential information cannot be recorded.

An object of the present invention is to provide confidential information of a desired amount of information on a print medium without the presence of the information being noticed by a third party, regardless of the number of pixels of public information to be printed on the print medium. It is to provide a confidential information recording method capable of recording.

The present invention also does not require a special printing device to print the image in which the confidential information is embedded, and does not require a special reproducing device to decode the image.
To provide a method for recording confidential information.

The present invention further provides a confidential information recording method capable of preventing the confidential information from being decrypted from the image data in which the confidential information is embedded even if the reproducing apparatus is handed over to a third party. To do.

[0008]

A feature of the invention described in claim 1 for solving the above-mentioned problems is a confidential information recording method for recording confidential information on a print medium on which a public information image is printed. There is a step of converting the image of the public information into dot-form public information data, a step of converting required confidential information into binarized confidential information data, and a step of converting the confidential information based on the binary confidential information data. Obtaining dot data for recording, preparing embedding position information of the dot data on the print medium, and data concerning an embedding method as encryption key information,
Embedding the dot data into the dot-form publicized information data by substituting based on the encryption key information to obtain composite information; creating print data according to the composite information data; And a step of printing an image according to the combined information data.

A feature of the invention described in claim 2 is a confidential information recording method for recording confidential information on a print medium,
Converting required confidential information into binarized confidential information data; obtaining dot data for recording the confidential information based on the binarized confidential information data; printing on a predetermined portion of the print medium To prepare the original dot data of the original image to be embedded, the step of preparing the embedding position information of the dot data in the original image and the data relating to the embedding method as encryption key information, and Creating one or a plurality of modified image data containing the confidential information by repeating a process of embedding the dot data according to the encryption key information, if necessary, the original dot image data and the modified image data And the original image on the print medium based on Serial in one or points including the steps of printing a plurality of the deformed image.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is for explaining an example of the embodiment of the invention of claim 1, and it is known to a third party that the public information image is printed by encoding required confidential information and printing the public information image. 9 is a flowchart showing a method of creating a confidential information recording document which is recorded by using a small dot pattern that does not exist. The method of creating a confidential information recording document shown by the flowchart of FIG. 1 is such that black dots, black, or white are formed on a plurality of blank areas having a predetermined area or more of a public information image to be printed on a paper surface which is a print medium. This is a method of recording required confidential information using a combination dot pattern. The area and number of blank areas, the dot patterns to be arranged on the blank areas, the number of arrangements and the arrangement method thereof can be freely set by the encryption key. However, it is desirable that the dot pattern has a resolution of 400 dpi or more and an arrangement density of 1% or less so that the recorded position cannot be visually detected by humans.

The method will be described below with reference to the flowchart of FIG. 1. First, in step 1, required confidential information is binarized to obtain binarized confidential information data (2 of confidential information).
Quantization process). The confidential information may be image data, computer program data, voice data, or tone data in addition to character data. In the next step 2, the binarized confidential information data obtained in step 1 is divided into blocks having an appropriate size (blocking processing of the binarized confidential information data). In the example shown in the figure, it is divided into blocks of 8 bits, but this is an example and any size may be used. In step 3, the encryption key is determined (encryption key determination process). This encryption key is the one created in step 2
A plurality of blocks (three in the present embodiment are included in the binarized confidential information data including an encryption code indicating a rule for rearranging the blocks of the binarized confidential information data. The rearrangement of one block) is executed in step 4, whereby confidential information blocks B1, B2, and B3 are obtained as dot data (block rearrangement processing). When the number of bits of the last confidential information block obtained by dividing the binarized confidential information data into a predetermined bit size is smaller than the predetermined bit size, "0" for the insufficient number of bits is set. A bit is added to the end to give a predetermined bit size. For the encryption here, for example, a conventional cryptosystem or a public key cryptosystem can be used. The number of confidential information blocks depends on the amount of confidential information, but is on average several thousand blocks.

Next, in step 5, the image of the public information, such as a non-confidential sentence or picture, which is supposed to be printed on the paper surface is made into dots, whereby the dot-formed public information data D
N1 is obtained (dotization process of public information image). In the next step 6, a blank area in the dot-form publicized information data DN1 for embedding the dot data in the dot-ized publicized information data DN1 obtained in step 5 by replacement is detected (a blank area detection process). The number of blank areas is the same as the number of blocks obtained by blocking the binarized confidential information data in step 2, and the number is 3 in the case of the present embodiment. This blank area is detected as a blank portion having a certain area or more. The blank area is also set in a blank area of a public information image such as a sentence or a picture, a minute area such as a space between lines of a sentence, a space between characters, or a blank area of a dot pattern representing a print pattern of one character. be able to. The size of the blank area may be set to a value given by the encryption key or may be fixed to a predetermined constant value.

If one blank area for embedding the dot data of one confidential information block is detected in this way, step 7 is entered, and a predetermined place of this blank area (for example, the upper left corner shown in FIG. 2). The reference point code DR1 for the reference point mark, which is always printed at one corner), and the above-described dot-ized public information data DN1 are combined, and the reference point code DR for the reference point mark is provided in the blank area.
Reference information data DS1 in which 1 is embedded by replacement is created (reference point code embedding processing). The reference point code is used to give a reference point mark for indicating the reference point for determining the embedding direction and order (vertical, horizontal) of the dot data of the confidential information block embedded in the blank area on the printing paper. It is a thing. This reference point code is embedded by replacement at a predetermined place in the blank area.

When the above-mentioned series of data processing in step 7 is completed, the process returns to step 6, the second blank area is detected in step 6, and the second blank area thus detected is again subjected to the second blank area. Th reference point code DR
2 is defined, and the reference information data DS1 in which the reference point code DR1 obtained in the execution of the previous step 7 is embedded
And the reference point code DR2 for this second blank area
And are combined in step 7 to obtain new reference information data DS1. In this way, the reference information data DS1 obtained in step 7 is used as the updated dot-ized public information data DN1 in the subsequent iterative processing of step 7, and the above-described processing in steps 6 and 7 is performed first. The same number of the obtained confidential information blocks (three in the present embodiment) is repeatedly executed (see FIG. 3). Therefore, the number L of repeated executions of steps 6 and 7 in this case is the same as the number of confidential information blocks. The reference point code limits the embedding direction and order (vertical and horizontal) of the dot data of the confidential information block, and may be a fixed value or may be uniquely given by an encryption key. Note that it is preferable to print at least one mark having asymmetry for distinguishing the top, bottom, left, and right of the paper on the paper, but at least one of the reference point marks is asymmetrical necessary for this kind of discrimination. It may be a mark having a property.

FIG. 2 shows an example of printing of the reference point mark on the blank area in an enlarged size so that each pixel can be identified. In FIG. 3, blank areas (a), (b), and (c) set in the gap of the public information image G on the paper F and these blank areas (a), (b), and (c) are printed. An example of the appearance of the reference point marks R1, R2, and R3 is shown. Here, for the sake of explanation, the reference point marks R1, R2, and R3 are represented as black dots of a size that can be visually recognized, but in reality, these reference point marks R1, R2, and R3 are extremely small and their presence is visually recognized. It is impossible to recognize the existence because the third party does not notice its existence.
The same applies to the dot data of confidential information blocks B1, B2, and B3 described later. Further, in FIG. 3, the number of blank areas is three for the sake of convenience of explanation, and the width thereof is shown to reach several centimeters square. It is a small blank area such as a gap between lines forming a character, and the number of blank areas is usually several thousand.

Returning to FIG. 1, the binarized confidential information data is blocked as described above, the blocks of the binarized confidential information data are rearranged by the encryption key, and the dot-disclosure public information data DN1. Detection of required number of blank areas for and reference point codes DR1 to DR for them
By the embedding by the replacement of 3, the three blank areas (a), (b), and (c) are secured, and the final reference information data DS1 obtained by adding the reference point mark to each blank area is obtained. Then, step 8 is entered. In step 8, for each blank area (a), (b) and (c) in which the reference point code of the reference information data DS1 finally obtained in step 7, is embedded, the confidential information blocks B1 to B3 are stored. A confidential information data embedding process for embedding each dot data by replacement in units of confidential information blocks is executed.

Next, the confidential information data embedding process in step 8 will be described with reference to the data example shown in FIG. Dot data (1010111) of the first confidential information block B1 determined in step 4
0) is embedded in the blank area (a) by replacement as follows. The blank area (a) is printed in white, so the pixel (dot) data is (0000 ...
・) And all become "0". The dot data of the first confidential information block B1 is coded bit by bit in the data string of "0" forming this blank area by referring to the rule regarding the data composition of the cryptographic key determined in step 3. The embedding process is executed by substituting the data in the embedding position according to the above. FIG. 3 is an enlarged view showing that the 8-bit dot data of the first confidential information block B1 shown in FIG. 1 is embedded in the blank area (a) of the reference information data DS1 by 1-bit substitution. There is. In FIG. 3, the underlined data looks discontinuous, but these data are the dot data of the first confidential information block B1.

The process of embedding the dot data indicating the confidential information for one confidential information block B1 in the predetermined blank area (a) in the reference information data DS1 has been described above. This process is obtained in step 4. The other confidential information blocks B2 and B3 are sequentially executed. That is, the combined information data obtained by the process of embedding the dot data of one confidential information block B1 in the predetermined blank area (a) in the reference information data DS1 becomes the updated reference information data DS1 in step 8. The confidential information block B2 is added to the updated reference information data DS1.
The dot data of will be embedded. In this way, the dot data of the confidential information block is embedded in the updated reference information data DS1 one after another. As a result, the dot data of the confidential information blocks B1, B2, and B3 shown in FIG. 3 are sequentially embedded in the blank areas (a), (b), and (c) by replacement according to the encryption key. The number of repeated executions of step 8 is also L times. Thus, in step 8, all confidential information blocks B
The final combined information data in which the contents of 1, B2, B3 are embedded in the reference information data DS1 by substitution is obtained. As can be seen from the above description, the number of bits of the blank area prepared for embedding the dot data of one confidential information block needs to be larger than the number of bits of the dot data of the confidential information block.

In step 9, dot-patterned print data is created according to the composite information data finally obtained in step 8. According to this print data, the image in which the confidential information is embedded in the appropriate blank area as described above is printed on the paper surface F (printing process of the combined information data). As described above, this printing can be performed using a printing machine, such as a laser printer, that digitally prints data of pixels having a resolution of about 400 dpi or higher. As a result, as shown in FIG. 3, the public information image G is printed on the paper surface F, and the blank areas (a), (b), and (c) are confidential with an arrangement density of 1% or less. Each dot data of the information blocks B1, B2, B3 is “0”
Is white and "1" is black at a predetermined position according to a predetermined rule, and the reference point marks R1, R2, R3 are also printed so that the predetermined position can be understood at the time of decoding.

Therefore, the blank areas (a), (b),
It cannot be visually discerned that an image according to the dot data of the reference point marks R1, R2, R3 and the confidential information blocks B1, B2, B3 is printed in (c), and the presence of the confidential information is detected by the third The person is not noticed.
Further, since the confidential information is embedded by using the blank area of the paper surface F, the amount of information that can be embedded is extremely large as compared with the conventional method of shifting the position of the pixel data of the public information image G. You can Therefore, for example, image data, audio data, musical sound data, or computer program data can be embedded by this method. Further, it is possible to copy a large amount of the same thing by a copying machine, and it is also possible to send it to a distant place by a facsimile machine.

In order to reproduce the confidential information based on the confidential information recording document in which the confidential information is embedded in this way, for example, by using an image scanner provided in the original reading section of a copying machine or the like, the paper surface of the confidential information is reproduced. Image information is read in pixel units, and the reference point mark is detected based on the data read in pixel units. In the illustrated example, the three reference point marks R1, R2, and R3 are detected, and a pixel on which eight white or black dots forming confidential information are printed by using the restoration key corresponding to the encryption key. The position can be specified by using the reference point marks R1, R2, R3 as a clue, and the 8-bit dot data of each of the embedded confidential information blocks B1, B2, B3 can be reproduced.

In this way, each confidential information block B
If the contents of 1, B2 and B3 are reproduced, these confidential information blocks B are reproduced by using the restoration key corresponding to the encryption key.
The rearrangement of 1, B2, and B3 can be performed in the reverse order of the case of step 4, and the state of the binarized confidential information data in step 1 can be restored. Based on the binarized confidential information data, the confidential information having a desired expression form can be reproduced.

As described above, since the encryption key and the decompression key are required to decrypt the confidential information, the confidential information can be decrypted only by passing the decryption device to a third party as in the case of using a dedicated decryption device. It has the advantage that it does not cause the inconvenience.

Although the confidential information blocks are rearranged in step 4 in the embodiment shown in FIG. 1, this procedure can be omitted if lower confidentiality is sufficient. Further, the public information image is not limited to a monochrome image and may be a color image, and required confidential information can be embedded in the color public information image by the same method as described with reference to FIGS. 1 to 3. .

Claim 1 described with reference to FIGS. 1 to 3.
In the embodiment of the invention described in (1), the case where the confidential information is embedded in an appropriate blank area such as a margin of the public information image G printed on the paper F has been described. Is not limited to this embodiment, the confidential information is not limited to the blank area, and may be embedded in an arbitrarily set area on the paper surface F regardless of the presence or absence of the public information image G. The processing procedure in that case will be described below with reference to FIG.

In the example of the embodiment shown in FIG. 4, confidential information is combined as a black dot or a combination dot pattern of black and white at an arbitrary position of the public information image. For example, when synthesizing the information bit "1" at a position overlapping the black dot of the public information image, the black dot is left as it is, and when synthesizing the information bit "0", it is replaced with the white dot. As a result, when the public information image includes many black dots and therefore has a small blank area, a large amount of confidential information can be embedded as compared with the embodiment shown in FIG. The method of embedding confidential information data in the public information image can be freely set by the encryption key. However, it is desirable that the resolution is 400 dpi or more and the confidential information embedding density is 1% or less so that the position where the dot pattern is recorded cannot be visually detected by humans.

In FIG. 4, the procedure from step 11 to step 15 is exactly the same as the procedure from step 1 to step 5 described with reference to FIG. Let's start with the explanation.

In step 16, the number of confidential information areas corresponding to the number of confidential information blocks obtained by dividing the binary confidential information data into blocks in step 12 is set. This will be specifically described in detail with reference to FIG. 5. Regardless of where on the paper F the public information image G is printed, the confidential information is processed in the same manner as in the embodiment shown in FIG. The confidential information area to be embedded in the public information image G is defined by determining the embedding area and the order of the embedding area by the encryption key. In the case of this embodiment, the confidential information is three confidential information blocks B.
Since it consists of 1, B2, B3, there are three confidential information areas X,
Y and Z are set (classified information area setting process). The set number L of confidential information areas here is equal to the number of confidential information blocks.

In step 17, first, a reference point code DR1 indicating a reference point mark R1 similar to that shown in FIG. 2 is prepared, and binarized dot-form public information data containing the public information image G as contents. Reference point code D for DN1
The reference information data DS1 is created by embedding by substitution so that R1 becomes the reference point mark R1 for indicating the reference position of the confidential information area X (reference point code embedding processing). Therefore, the image based on the reference information data DS1 is the public information image G to which the reference point mark R1 is added. This reference information data DS1 is obtained in step 17
The updated dot-ized public information data DN1 in FIG.

Next, step 17 is executed again for the process of embedding the second reference point code DR2 in the second confidential information area. Dotized public information data DN in which the reference point code DR2 in this case is embedded
1 is the reference information data DS1 updated by the process of step 17 immediately before. In this way, the reference information data DS1 obtained in step 17 is used as the updated dot-ized public information data DN1 in the subsequent iterative processing of step 17, and the above-mentioned processing in step 17 is obtained first. The same number of the confidential information areas (three in the present embodiment) is repeatedly executed. Therefore, the number L of repeated executions of step 17 in this case is the same as the number of confidential information blocks. As a result, as shown in FIG. 5, the three confidential information areas X,
Final reference information data DS1 in which reference point codes DR1, DR2, DR3 for reference point marks R1, R2, R3 are embedded in Y and Z by replacement, respectively, are created,
Step 18 is entered next.

In FIG. 5, the reference point mark R1 is shown as a black dot of a size that can be visually recognized for the sake of description, but in reality, the reference point mark R1 is extremely small and its presence is visually recognized. Because it is impossible, a third party does not notice its existence. Other reference point marks R2 and R3, and a confidential information block B described later.
Similarly, it is not possible to visually recognize the presence of the dot patterns of the dot data of 1, B2, and B3. Further, in the example shown in FIG. 5, the number of confidential information areas is three for simplification of description, and the area thereof is shown to be several centimeters square. The information area is a minute area like the blank area described above, and the number of confidential information areas is usually about several thousand. As can be seen from the above description, the number of bits of the confidential information area prepared for embedding the dot data of one confidential information block needs to be larger than the number of bits of the dot data of the confidential information block.

In step 18, for each confidential information area X, Y, Z in which the reference point code of the final reference information data DS1 obtained in step 17 is embedded, the dots of the confidential information blocks B1, B2, B3 are set. The confidential information data embedding process for embedding the data by replacement is repeated L times.

Explaining in accordance with the bit example shown in FIG. 4, the dot data (10101110) of the first confidential information block B1 determined in step 14
Are embedded in the data (10101100 ...) Of the confidential information area X of the reference information data DS1 by bit-by-bit data substitution at bit positions according to the rule indicated by the encryption key. In this case, unlike the case of the embodiment shown in FIG. 1, the data of the confidential information area X has a form in which information of "1" and "0" is randomly arranged. Therefore, if the content of the dot data in the confidential information area X before the replacement of the embedding position designated by the encryption key is the same as the content of the dot data of the confidential information block to be embedded therein, the content is left as it is and the content is different. Only in this case, the content of the dot data in the confidential information area X is changed so as to match the content of the dot data in the confidential information block.

This will be specifically described with reference to FIG. 6A is an enlarged view of the confidential information area X in the reference information data in which the dot data of the confidential information block is to be embedded, and a part of the image data KD of the public information image G is shown by pixel data. There is. Here, white indicates the portion where the pixel data is “0”, and the shaded area indicates the portion where the pixel data is “1”.
Is shown. 6B, the dot data (000) of the confidential information block B1 is stored in the confidential information area X of FIG.
(10011100100110100 ...) With the reference point code DR1 embedded therein is a specific example showing the state of pixel data. From this example, if the dot data of the confidential information area X at the embedding position designated by the encryption key is the same as the dot data of the confidential information block B1, the dot data is left as it is, and only when they are different, the dot data of the confidential information block B1 is changed. It can be seen that the embedding of the data is performed by the replacement of changing the original dot data so as to match.

In this way, when the dot data of the confidential information block B1 is embedded in the reference information data DS1 by substitution to obtain the combined information data, the step 1 is performed again.
8 is executed, and the dot data of the next confidential information block B2 is embedded. In this case, confidential information block B
The reference information data in which the dot data of 2 is embedded is the combined information data obtained by the process of step 18 immediately before. That is, the combined information data obtained in step 18 is used as the updated reference information data in the processing of the further step 18 which is subsequently executed.

The process of step 18 is repeatedly executed as described above for the number of confidential information blocks. As a result, even in the other confidential information areas Y and Z, the confidential information block B
The dot data of 2 and B3 are similarly processed according to the encryption key, and required confidential information is embedded in the public information image G as a dot pattern. Thus, step 1
8, all confidential information blocks B1, B2, B3
The composite information data is obtained by substituting the dot data of 1 to the reference information data DS1 by substitution.

In step 19, the dot-patterned print data is created according to the composite information data finally obtained in step 18. According to this print data,
The image in which the confidential information is embedded in the appropriate confidential information area as described above is printed on the paper surface F (printing process of the combined information data). As described above, this printing can be performed using a printing machine, such as a laser printer, that digitally prints data of pixels having a resolution of about 400 dpi or higher.

According to the processing according to FIG. 4, the advantages described above in the case of FIG. 1 can be directly enjoyed. Even in the case shown in FIG. 4, the step 14 of rearranging the confidential information blocks can be omitted.

Claim 1 described with reference to FIGS. 1 to 6.
In each of the embodiments of the invention described in (1), the case where the confidential information is embedded as a black and white dot pattern in the public information image printed on a print medium such as a paper surface has been described. However, the invention according to claim 1 is not limited to this embodiment, and the confidential information may be embedded as a color dot pattern. An example will be described with reference to FIGS. 7 to 9.

In the example of the embodiment according to the processing procedure shown in FIG. 7, the content of the confidential information is embedded by substitution as a color dot pattern of 8 colors in an arbitrary position of the color public information image. When embedding a color dot of the same color at a position overlapping the color dot of the public information image, the color dot is left as it is, and when a color dot of a different color is embedded, the color dot of the different color is replaced.
As a result, a large amount of confidential information can be embedded even if there are few white areas in the public information image. The method of embedding the confidential information data in the color public information image can be freely set by the encryption key. However, to prevent humans from visually detecting the position where the color dot pattern that complies with confidential information is embedded,
For example, it is desirable that the resolution is 400 dpi or more and the confidential information embedding density is 1% or less.

The method will be described below with reference to the flowchart of FIG. 7. First, in step 21, required confidential information is binarized to obtain binarized confidential information data (binary processing of confidential information). The confidential information may be image data, computer program data, voice data, or tone data in addition to character data. Next step 22
Then, the binarized confidential information data obtained in step 21 is divided into blocks of K × J bits to form a large block of confidential information (blocking process of binarized confidential information data). Here, K represents the number of unit bits for color information conversion determined by the number of colors of color dots used for embedding the binarized confidential information data. For example, if you use 8 color dots
In the case of color, K = 3 because color information is converted in 3-bit units, and in the case of 16 colors, K = 4 because color information conversion is in 4-bit units. Since conversion is performed, K = 5, and when 64 colors are used, color information conversion is performed in 6-bit units, so K = 6. As can be seen from the above description, in the present embodiment, one confidential information block is composed of the number of unit bits for color information conversion,
The K-bit information is dot data indicating the contents of this confidential information block. Note that K is also the number of bits of the confidential information block. Specifically, the content of one confidential information block is expressed as one color dot such as red dot, black dot, white dot, .... In order to scramble a plurality of confidential information blocks as a unit, the large confidential information block is divided into blocks of K × J bits so that the large confidential information blocks include a plurality of confidential information blocks. . That is, J indicates the number of confidential information blocks in the large confidential information block, and when J = 1, the large confidential information block and the confidential information block have the same contents. If the number of bits of the final large block of confidential information obtained by dividing the binarized confidential information data into blocks of K × J bits and dividing the block is K × J bits or less, K × J bits "0" bit is added to the end of the last confidential information large block so that the number of bits of the last confidential information large block is also K × J bits. This makes each K
A plurality of large blocks of confidential information of × J bits are created. In step 23, the encryption key is determined (encryption key determination process). This encryption key includes an encryption code indicating a rule for rearranging the large blocks of confidential information obtained by dividing the binarized confidential information data obtained in step 22 into K × J bits, and according to this. The rearrangement method is designated, and the plurality of large confidential information blocks obtained in step 22 are rearranged in step 24 (block rearrangement processing). For the encryption here, for example, a conventional cryptosystem or a public key cryptosystem can be used. Although it depends on the amount of confidential information, it is usually several thousand blocks, and the large confidential information block includes several thousand confidential information blocks.

In step 25, the K × J-bit binary data in each large block of confidential information is divided into K-bit units, and the binary data in K-bit units is converted into color information according to the encryption key obtained in step 23. To (color information conversion processing). In this embodiment, since eight color dots are used, K = 3 is set, and the 3-bit binary data is converted into any one of the numerical values 1 to 8. In this way, the binary data in the first large confidential information block is converted into color dot information, and confidential information blocks BC1, BC2, BC3, ... Containing color dot information are obtained in step 25. . Second, third ...
The same applies to the large block of confidential information. The color of the color dots is represented by 1 for white, 2 for red, 3 for blue, ...
・, 8 can be set arbitrarily such as black. In addition, in the color setting method using the encryption key, “000” is represented by 8 in black, “001” is represented by 3 in blue, and “01” is represented by “01”.
It is possible to appropriately adopt a method such that "0" is represented by 2 as red and "111" is represented by 1 as white.

Next, in step 26, the color public information image such as a non-confidential text or picture to be printed on the paper F is converted into color dots to create color dot public information data DNC1. Yes (dotization process of color public information image). In step 27, step 22
Set the confidential information area for the large number of large blocks of confidential information obtained in. This will be specifically described in detail with reference to FIG. 8. Regardless of where on the paper F the color public information image GC is printed, required confidential information is provided as described below to the public information image. The confidential information area to be embedded in the GC is determined by determining the area to be embedded and the order of the embedded area by the encryption key (setting processing of the confidential information area). In the case of this embodiment, the confidential information is 3
Since it consists of one large block of confidential information, three confidential information areas XC, YC and ZC are set.

In step 28, first, the color reference point code DRC1 indicating the reference point mark is prepared, and the reference point code is added to the dotted public information data DNC1 which is the color dot data containing the public information image GC. D
RC1 is combined so as to become a color reference point mark RC1 for indicating the reference position of the confidential information area XC, and reference information data DSC1 is created (reference point code embedding processing). Therefore, the content of the reference information data DSC1 is that the reference point mark RC1 (based on the reference point code DRC1 embedded by replacement) is added to the public information image GC.

Next, step 28 is executed again for the process of embedding the reference point code DRC2 in the second confidential information area YC. Dotized public information data DNC in which the reference point code DRC2 in this case is embedded
1 is the reference information data DSC1 updated by the process of step 28 immediately before. In this way, the reference information data DSC1 obtained in step 28 is used as the updated dot-ized public information data DNC1 in the subsequent iterative processing of step 28, and the above-mentioned processing in step 28 is obtained previously. It is repeatedly executed by the same number as the number of confidential information areas (three in this embodiment).

As a result, as shown in FIG. 8, the reference point marks RC1 and R are provided in the three confidential information areas XC, YC and ZC.
The final reference information data DSC1 in which C2 and RC3 are respectively embedded by substitution is created, and the next step 2
Enter 9. The number L of times of repeating the step 28 can be represented by (W + KJ-1) / KJ. Here, W is the total number of bits of the binarized confidential information, K is the number of unit bits for color information conversion determined by the number of colors of the color dots used for embedding the binarized confidential information data, and J is the confidential information. This is the number of confidential information blocks included in a large block. In the example shown in FIG. 8, the number of confidential information areas is three for the sake of simplification of description, and the area thereof is shown to extend to several centimeters square. Is a minute area like the blank area described above, and the number of confidential information areas is usually about several thousand.

Here, in FIG. 8, the reference point mark RC1 is shown as a black dot of a size that can be visually recognized for the sake of description, but in reality, the reference point mark RC1 is extremely small and its existence is visually recognized. Since it is a color mark that is impossible to do, a third party does not notice its existence. Similarly, the presence of the other reference point marks RC2 and RC3 and the color dot pattern indicating the contents of each confidential information block cannot be visually recognized.

In step 29, each confidential information area XC, Y of the reference information data DSC1 obtained in step 28
Confidential information data embedding processing for embedding as dot data indicating the contents of a plurality of confidential information blocks included in the corresponding large confidential information block into color dot data by substituting each of them is performed on C and ZC.

Explaining in accordance with the data example shown in FIG. 7, the color dot data (52355645 ...) Of a plurality of confidential information blocks included in the first large confidential information block defined in step 25 is obtained. Data in the confidential information area XC portion of the reference information data DSC1 (32
14568123215 ...) is embedded in the bit position according to a predetermined rule determined by the encryption key by data replacement. In this case, since the confidential information area XC is not a white area, the color dot data 1
The numerical information of 8 is in a lined up irregularly. Therefore, if the content of the color dot data before replacement of the confidential information area XC at the embedding position designated by the encryption key is the same as the content of the color dot data of the confidential information block to be embedded therein, leave it as it is, and if they are different. Only, the color dot data of the confidential information area XC is changed by substituting it to match the color dot data of the confidential information block.

This will be specifically described with reference to FIG. FIG. 9A is an enlarged view of the confidential information area XC provided in the reference information data DSC1 for embedding the color dot data indicating each content of the plurality of confidential information blocks included in the required large confidential information block. Yes, a part of the public information image GC there is shown in pixel units.
Here, white indicates a white portion where the pixel data is “1”,
A shaded portion indicates a portion where the pixel data is data other than 1. FIG. 9B shows the data contents of the large block of confidential information (115111) in the confidential information area XC shown in FIG.
1811111 ...) Is embedded with the reference point code DRC1 and is a specific example showing a state of pixel data. From this example, it is understood that the color dot data of the confidential information area XC at the embedding position designated by the encryption key is replaced with the color dot data of the confidential information block BC1. As can be seen from the above description, the number of bits of the confidential information area prepared for embedding the dot data of one large confidential information block needs to be larger than the number of bits of the dot data of the large confidential information block. is there.

In this way, when the dot data of a plurality of confidential information blocks of one large confidential information block is embedded in the reference information data DSC1 by substitution to obtain the synthetic information data, step 29 is executed again, and the next step is executed. Dot data of a plurality of confidential information blocks in the large confidential information block is embedded. The reference information data DSC1 in which the dot data of a plurality of confidential information blocks of this large confidential information block are embedded is the step 29 immediately before.
It is the combined information data obtained by the process of. That is, the composite information data obtained in step 29 is
It is used as the updated reference information data in the processing of the further step 29 executed subsequently.

The processing of step 29 is repeatedly executed as many times as the number of the confidential information large blocks obtained in step 22 as described above, and the plurality of confidential information of the corresponding confidential information large blocks are also provided in the other confidential information areas YC and ZC. By similarly processing the color dot data of the block according to the encryption key, required confidential information is embedded in the public information image GC. Thus, in step 29,
Composite information data is obtained in which dot data of all confidential information blocks are embedded in the reference information data DSC1 by substitution in units of large confidential information blocks. In step 30, dot-patterned print data is created according to this composite information data. An image including confidential information is printed on the paper surface F according to the print data (printing process of composite information data). As described above, this printing can be performed using a printing machine, such as a laser printer, that digitally prints data of pixels having a resolution of about 400 dpi or higher.

FIG. 10 is a flow chart for explaining an example of the embodiment of the invention described in claim 2. The form of the confidential information recording method shown by the flowchart of FIG. 10 is one original image, and a plurality of modified images obtained by embedding the original mark data representing the original image by replacing the dot data of the confidential information block by replacement. Is a method of recording confidential information by combining with the public information image. In this case, the modified images may be overlapped on the public information image. At the time of reproduction, confidential information is extracted by comparing the difference between the original image and the deformed image with pixel data. A method of arranging one or more images in which confidential information is embedded on the public information image can be freely set by an encryption key.
The dot pattern of the confidential information block indicating the confidential information makes it impossible for a human to visually detect the recorded position. Therefore, for example, it is desirable that the arrangement density is 1% or less at a resolution of 400 dpi or more.

The method will be specifically described below with reference to the flow chart of FIG. 10. First, in step 31, required confidential information is binarized to obtain binarized confidential information data (binarization processing of confidential information). In addition to character data, this confidential information includes image data, computer program data,
It may be any data such as voice data or tone data. In the next step 32, the binarized confidential information data obtained in step 31 is divided into blocks of appropriate size (blocking process of binarized confidential information data). In the example shown in the figure, it is divided into blocks of 8 bits, but this is an example and any size may be used. In step 33, the encryption key is determined (encryption key determination process). This encryption key contains an encryption code indicating a rule for performing sorting after blocking the binarized confidential information data created in step 32, and accordingly, in step 32.
The rearrangement of the blocks of the binarized confidential information data obtained in (1) is executed in step 34 (block rearrangement processing). For the encryption here, for example, a conventional encryption system or a public key encryption system can be used. In this embodiment, this results in a large number of sensitive information blocks B1, B2, B3, ...
., Bn are obtained as dot data. If the number of bits of the last confidential information block obtained by dividing the binarized confidential information data into 8 bits is smaller than 8 bits, the bits of "0" for the insufficient number of bits are added to the end. To 8 bits. As a result, the number of bits of all confidential information blocks becomes 8 bits. The same applies when the number of bits of the confidential information block is set to a value other than 8 bits.

Next, in step 35, the open information image such as a non-confidential sentence, picture, etc. to be printed on the paper surface F which is the print medium is binarized to thereby make it dot-opened. The information data DN1 is obtained (dotization processing of the public information image). In step 36, the confidential information blocks B1, B2, B3, ...
.. To obtain the dot data of the original image for embedding the dot data of Bn, the original mark M
The image of 0 is binarized to obtain the original mark data (dot processing of the original image).

In this embodiment, the original mark M
For 0, a predetermined symbol mark is selected as shown in FIG. 11, and the original mark data obtained as the binarized data in step 36 is replaced with an arbitrary blank area of the dotted public information data DN1 in step 37. Are embedded by using the reference information data DS1 (original mark embedding processing). The original mark data may be embedded at a predetermined fixed position in the reference information data DS1 or may be embedded at a position designated by the encryption key. However, the area to be embedded must be a blank area. In FIG. 11, the public information image G is a print image according to the dotted public information data DN1, and the original mark M0 is a print image according to the original mark data.

In this way, after the reference information data DS1 is obtained in step 37, the process proceeds to step 38, and the mark data Z1 in which the dot data of the confidential information block B1 is embedded in the original mark data by substitution is first created. . The method of creating the mark data Z1 is the same as the method of embedding the dot data of the confidential information block in the confidential information area described with reference to FIG. Therefore,
The position of embedding the dot data of the confidential information block B1 in the original mark data may be fixed (fixed direction, order) or may be embedded in the direction and order specified by the encryption key. In this case, the embedding process of the confidential information data is performed in the designated direction from the mark at the designated position. This mark data Z1 is used as reference information data DS1
Further, the data embedding process is performed to embed the mark data Z1 in the reference information data DS1 to obtain combined information data. This combined information data becomes the updated reference information data DS1 in step 38. This data embedding process is also similar to the method of embedding the dot data of the confidential information block in the confidential information area described with reference to FIG. Next, by the same procedure as described above, the confidential information block B2
Mark data Z2 in which the dot data of
Is embedded in the latest composite information data in which is embedded by a similar method to form composite information data including mark data Z1 and Z2. In this way, step 38 is repeatedly executed, and synthetic information data including mark data Z3, Z4, ... In which the dot data of the confidential information block B3, the confidential information block B4, ... Information data embedding process). Note that these mark data Z1 to Zn do not necessarily have to be blank areas on the paper surface, and may be embedded so as to overlap the public information image G (see FIG. 11).

The processing in step 38 will be described in more detail by way of a specific example. Dot data (1) which is the data content of the confidential information block B1 obtained in step 34 is obtained.
(0101110) and the dot data (001) which is the data content of the original mark data obtained in step 36.
(0111011 ...) And the encryption key determined in step 33, a process of embedding the dot data of the confidential information block B1 in the original mark data by substitution at the position indicated by the encryption key is first executed, and as a result, the confidential information block The mark data Z1 in which the dot data of B1 is embedded is obtained.

In this case, the dot data of the confidential information block is embedded in the black dot (1) of the original mark. In this embedding, when the value of the confidential information block is "1", the black dot (1) of the original mark at the embedding position is set to "0", while when the value of the confidential information block is "0". Is performed by leaving the black dot (1) of the original mark at the embedding location as it is. As can be seen from the above description, the number of bits of the original mark data prepared for embedding the dot data of one confidential information block needs to be larger than the number of bits of the dot data of the confidential information block.

Thereafter, the mark data (00001000 ...) Obtained in this way is used as the reference information data DS.
Combined with 1 to obtain combined information data. This synthesis is performed by embedding the mark data in the reference information data DS1 by substitution. Embedding by this replacement is
When the value of the mark data is "1", it is set to "1" regardless of whether the content of the reference information data in the embedding portion is "1" or "0". On the other hand, when the value of the mark data is “0” and the value of the original mark data is “1”, whether the content of the reference information data at the embedded portion is “1” or “0” is “0”. "
If the value of the mark data is “0” and the value of the original mark data is also “0”, the reference information data at the embedding point will be data even if the content is “1” or “0”. Will not be replaced.

As described above, since the density of the dot data of the confidential information block B1 in the binarized original mark data is considered to be 1% or less, it is printed according to the mark data Z1. Mark M1
Is the same as the original mark M0 in appearance, and a third party cannot discriminate that the confidential information is embedded in the mark M1 only by visually observing the mark M1. The mark data Z1 thus obtained is combined with the reference information data including the original mark data obtained in step 37, and this combined data is obtained as combined information data.

The processing described above is then performed based on the dot data of the confidential information block B2, and the processing of sequentially embedding the dot data of the confidential information block B2 in the original mark data at the embedding positions indicated by the encryption key is executed. Then, the mark data Z2 is obtained. The mark data Z2 is further combined with the combined information data including the mark data Z1 to obtain updated combined information data.

Further, the same process is performed based on the dot data of the confidential information block B3, and the process of sequentially embedding the dot data of the confidential information block B3 in the original mark data at the embedding position indicated by the encryption key,
As a result, the mark data Z3 is obtained. The mark data Z3 is further combined with the combination information data including the mark data Z1 and Z2. In this way, the mark data Z
Up to n are embedded and the combined information data is combined. Here, the number of marks that can be printed on one page and the mark data Z1
~ Does not necessarily match the total number of Zn. However, even in such a case, it is preferable that the mark is printed over the entire page. This is because it is unnatural that only a part of the mark is printed, which indicates the existence of confidential information. Therefore, even after the synthesis of the mark data Zn is completed, the dummy marks MN1 to MNm in which the confidential information is not embedded are sequentially synthesized,
Make sure the mark is printed over the entire page. In this way, final composite information data including the marks M1 to Mn corresponding to the mark data Z1 to Zn and the dummy marks MN1 to MNm is obtained (see FIG. 11). Therefore, the number of confidential information blocks is equal to or smaller than the number of marks for embedding the confidential information. Here, the number L of repeated executions of step 38 is 1
It is indicated by the number of marks n + m that can be printed on a page. That is, it is equal to a value obtained by adding the number n of marks in which the dot information of the confidential information block is embedded and the number m of dummy marks in which the dot data of the confidential information block is not embedded.

At step 39, dot-patterned print data is created according to the composite information data obtained at step 38, and the public information image in which the confidential information is embedded is printed based on the print data (composite information). Data printing process). In this way, the paper F is shown in FIG.
In addition to the public information image G, the original marks M0 arranged in the blank area and the marks M1 to M according to the mark data Z1 to Zn in which confidential information is embedded, as shown in FIG.
n and a dummy mark M in which confidential information is not embedded
N1 to MNm are arranged and printed. Marks M1 to M
The confidential information is embedded in n in units of pixels with a resolution of 400 dpi, and the density of the confidential information embedded is set to 1% or less.
Even if you look at Mn, you do not notice the existence of confidential information. In FIG. 11, the print positions of the marks M0 to Mn and the dummy marks MN1 to MNm are aligned and arranged over the entire page. However, the print positions of these marks are not limited to this, and any positions It is possible to print, and only a part of it may be printed.

In order to reproduce the confidential information based on the document in which the confidential information is created in this manner, the image information on the paper surface is pixel-pixel-shaped by an image scanner provided in a document reading unit of a copying machine or the like. Each mark data Z is read based on the data read in units of pixels.
1 to Zn are compared with the original mark data. Then, the 8-bit data content of each confidential information block B1, B2, B3, ..., Bn is regenerated by detecting the pixel difference at a predetermined embedding position using the restoration key corresponding to the encryption key. can do.

In this way, the confidential information block B1,
When each dot data of B2, B3, ..., Bn is reproduced, the confidential information blocks B1, B2, B3, ..., Bn are rearranged by using the restoration key corresponding to the encryption key. Reverse the procedure of step 34, step 3
The state of the binary confidential information data in 1 can be returned. Based on this binarized confidential information data, the confidential information in a desired expression form can be decrypted.

Since the encryption key and the decompression key are necessary to decrypt the confidential information, the confidential information can be decrypted only by passing the decryption device to a third party as in the case of using a dedicated decryption device. It has the advantage of not causing the inconvenience.

Although the confidential information blocks are rearranged in step 34 in the embodiment shown in FIG. 10, this procedure may be omitted.

In the embodiment of the invention described in claim 2 described with reference to FIGS. 10 to 11, the case where the confidential information is embedded as a black and white dot pattern in the original mark printed on the print medium such as a paper surface will be described. did. However, the invention according to claim 2 is not limited to this embodiment, and the confidential information may be embedded as a color dot pattern. The embodiment in that case will be described below. This will be described with reference to FIGS. 12 to 15.

The embodiment shown in FIG. 12 is such that the public information and the original mark are color images, and the binarized confidential information data is converted into color dot data and embedded in the original mark data. The embodiment is greatly different from the embodiment shown in FIG.

The method will be described below with reference to the flowchart of FIG. 12. First, in step 41, required confidential information is binarized to obtain binarized confidential information data (binarization processing of confidential information). The confidential information may be image data, computer program data, voice data, or tone data in addition to character data. Next step 4
In step 2, the binarized confidential information data obtained in step 41 is blocked into a size of K × J bits to form a large block of confidential information (blocking process of binarized confidential information data). Here, K represents the number of unit bits for color information conversion determined by the number of colors of color dots used for embedding the binarized confidential information data. For example, if you use 8 color dots
In the case of color, K = 3 because color information is converted in 3-bit units, and in the case of 16 colors, K = 4 because color information conversion is in 4-bit units. Since conversion is performed, K = 5, and when 64 colors are used, color information conversion is performed in 6-bit units, so K = 6. As can be seen from the above description, in the present embodiment, one confidential information block is composed of the number of unit bits for color information conversion,
The K-bit information is dot data indicating the contents of this confidential information block. Specifically, the contents of one confidential information block are red dots, black dots, white dots, ...
・ It is expressed as one color dot such as. Then, in order to enable scrambling in units of a plurality of confidential information blocks, the confidential information large block for rearrangement is divided into blocks of K × J bits so that a plurality of confidential information blocks are included. It has been done. That is, J indicates the number of confidential information blocks in the large confidential information block, and when J = 1, the large confidential information block and the confidential information block have the same contents.
If the number of bits of the final large block of confidential information obtained by dividing the binarized confidential information data into blocks of K × J bits and dividing the block is K × J bits or less, K × J bits Therefore, the number of bits of the last large confidential information block is also set to K × J bits by adding a bit of “0” to the end. This makes each K ×
Multiple large blocks of confidential information that are J bits are created.
In step 43, the encryption key is determined (encryption key determination process). This encryption key includes an encryption code indicating a rule for rearranging the large block of confidential information obtained by dividing the binarized confidential information data obtained in step 42 into K × J bits, and according to this. The rearrangement method is designated, and the plurality of confidential large information blocks obtained in step 42 are rearranged in step 44 (block rearrangement processing). For the encryption here, for example, a conventional cryptosystem or a public key cryptosystem can be used. Although it depends on the amount of confidential information, it is usually several thousand blocks, and the large confidential information block includes several thousand confidential information blocks.

In step 45, the K × J bit binary data in each confidential information block is divided into K bit units,
Binary data is converted into color information in units of K bits according to the encryption key obtained in step 43 (color information conversion processing).
In this embodiment, since eight color dots are used, K = 3 is set, and the 3-bit binary data is converted into any one of the numerical values 1 to 8. The binary data in the first large block of confidential information is converted into color dot information, and a large number of confidential information blocks containing the color dot information are obtained in step 45. 2nd, 3rd,
The same applies to the large block of confidential information. The color dots are represented by 1 for white, 2 for red, 3 for blue,
..., 8 can be set arbitrarily such as black.
For the color setting method using the encryption key, set "000" to 8
As black, "001" as 3 as blue,
It is possible to appropriately adopt a method in which “10” is represented by 2 as red and “111” as 1 as white.

Next, in step 46, the open public information image GC that is not confidential and is to be printed on the paper F in step 46 is color-dotted to form dot public information data DNC1. (Doting process of color public information image). In step 47, the original mark MC0 of a predetermined color is converted into color dots to obtain color original mark data which is dot data (dot processing of the original color image).

In this embodiment, the original mark M
As for C0, a symbol mark is selected as shown in FIG. 14, and the original mark data obtained in step 47 is the dot-form publicized information data DN in step 48.
It is embedded in an arbitrary white area of C1 by replacement, and this is used as reference information data DSC1 (original mark embedding processing). The original mark data may be embedded at a predetermined fixed position in the reference information data DSC1, or may be embedded at a position designated by the encryption key. However, the embedded area must be a white area. In FIG. 14, the public information image GC is a print image according to the dotted public information data DNC1, and the original mark MC0 is a print image according to the original mark data.

In this way, after the reference information data DSC1 is obtained in step 48, the process proceeds to step 49, and the original mark data is replaced with each dot data of the confidential information block included in the first large confidential information block. The mark data ZC1 embedded by is first created.
The method of creating this mark data ZC1 is basically as shown in FIG.
This is the same as the method of embedding the confidential information block dot data in the confidential information area described based on the above. Therefore, the position of embedding each dot data of the confidential information block included in the first confidential information large block into the original mark data may be fixed (determined direction, order) or the direction and order specified by the encryption key. You may embed with. In this case, the confidential information is embedded in the designated direction from the mark at the designated position.

Next, a method of embedding the color dot data indicating the contents of the confidential information block in the original mark data will be described. In the case of the embodiment shown in FIG. 7, the color dot data is embedded by simple replacement. However, in the present embodiment, data replacement is performed by changing the color dot data of the original mark data at the embedding position according to the content of the color dot data of the confidential information block to be embedded. Has become. This will be described with reference to FIG. Now, when embedding the dot data of 5 of the confidential information block in the bit position where the dot data of the original mark data has the content of 6, the content of 3 is located at the fifth position in the clockwise direction from 6 in FIG. The dot data to be embedded is set as the content of the dot data to be embedded, and 6 is replaced with 3. Similarly, when the dot data having the content of 2 in the confidential information block is embedded in the bit position where the content of the dot data of the original mark data is 2, it is located at the second position 4 clockwise from 2 in FIG.
The dot data having the content of 4 is replaced with the content of the dot data to be embedded, and 4 is replaced with 3 (see FIG. 12). In addition,
This replacement method is an example, and it goes without saying that other appropriate rules may be used.

The mark data Z obtained as described above
In order to embed C1 in the reference information data DSC1, further data embedding processing is executed, and the mark data ZC1 is embedded in the reference information data DNC1 according to the rule shown in FIG. processing). This combined information data becomes the updated reference information data DSC1 in the subsequent processing of step 49. Next, by the same procedure as described above, the mark data ZC in which the dot data of a plurality of confidential information blocks included in the second large confidential information block is embedded in the original mark data.
2 is created, and this mark data ZC2 is embedded in the reference information data DSC1 that has already been updated by embedding the mark data ZC1 by the same method.
The combined information data includes C1 and ZC2. In this way, step 49 is repeatedly executed for the number of large blocks of confidential information obtained in step 42, and the final dot data of the confidential information block includes the mark data ZC3, ZC4, ... Composite information data is obtained. In addition, these mark data ZC1 to ZC
n does not necessarily have to be a white area on the paper surface, and may be embedded so as to overlap the public information image GC (see FIG. 14).

The processing in step 49 will be described in more detail by way of a specific example.
Each dot data (52355645 ...) Of the confidential information block included in the th confidential information large block and the original mark data (161181) obtained in step 47.
2 ... 8) and the encryption key determined in step 43, a process of first embedding each dot data of these confidential information blocks in the original mark data by substitution at the position indicated by the encryption key is executed, and The mark data ZC1 (14) in which the dot data of the confidential information block included in the first confidential information large block is embedded
11814 ... 8) is obtained. The data replacement rule at this time is as described with reference to FIG. As can be seen from the above description, the number of bits of the original mark data prepared for embedding the dot data of one large confidential information block must be larger than the number of bits of the dot data of the large large confidential information block. is there.

FIG. 15A is an enlarged view of a part of the color original mark MC0 in which the color dot data of the confidential information block is to be embedded. Here, a part of the original mark MC0 is shown in pixel units. Here, white indicates a white portion where the pixel data is “1”, and a shaded portion indicates a portion where the pixel data is data other than “1”. FIG. 15B shows bit data (5235) of the confidential information block belonging to the first large confidential information block in the original mark MC0 shown in FIG.
645 ...) is a specific example showing a change in pixel data. From this example, it can be seen that the color dot data of the original mark MC0 at the embedding position designated by the encryption key is replaced with each dot data of the confidential information block.

Returning to FIG. 12, the mark data ZC1 (1311814 ... 8) thus obtained is used as the reference information data DSC1 (.121) obtained at step 48.
4568123215 ...) And synthetic | combination information data (* 325445832215 ...) is obtained. In this combination, the mark data ZC1 is used as the reference information data DSC.
It is executed by embedding by substitution with 1. The embedding by this replacement is the same as the case of embedding the contents of the confidential information block in the original mark MC0. The synthesized information data obtained here becomes the updated reference information data DSC1.

The above-described processing is performed next in the second
The process is performed based on the dot data of the confidential information block belonging to the th confidential information large block, and the process of sequentially embedding the dot data in the original mark data at the embedding position indicated by the encryption key is performed, thereby obtaining the mark data ZC2. The mark data ZC2 is further combined with the combination information data including the previously obtained mark data ZC1 to obtain updated combination information data.

Furthermore, based on the dot data contents of the confidential information block belonging to the third large confidential information block,
A process of sequentially embedding these dot data in the original mark data at the embedding positions indicated by the encryption key is performed, and the mark data ZC3 is obtained. The mark data ZC3 further includes mark data ZC1 and ZC1.
It is combined with the combined information data including 2. In this way, the mark data ZCn is embedded and the combined information data is combined.

At step 50, dot-patterned print data is created according to the composite information data obtained at step 49, and an image is printed based on the print data (composite information data print processing). As shown in FIG. 14, the image printed in this manner follows the public information image GC, the original mark MC0 placed in the white area, and the mark data ZC1 to ZCn in which confidential information is embedded. Marks MC1 to MCn and dummy marks MNC1 to M in which confidential information is not embedded
NCm and are arranged as shown in the figure and printed. here,
The number L of repeated executions of step 49 is indicated by the number n + m of marks that can be printed on one page. That is, the number n of marks in which the dot data of the confidential information block is embedded,
It is equal to a value obtained by adding the number m of dummy marks in which the dot data of the confidential information block is not embedded.

The effects of the confidential information recording method described above are summarized below. (1) A third party does not understand the existence of confidential information recorded on paper. (2) Even if a third party obtains the playback device, it is unlikely that the confidential information will be decrypted. (3) Since a large amount of confidential information is embedded, digital information such as character information, audio information, image information, and computer programs can be combined and recorded or reproduced on paper. (4) No special recording / reproducing device is required. (5) Because it is printed on paper and easy to copy,
It is possible to add, correct and delete confidential information by cutting and pasting. (6) A large number of copies can be made in a short time by using a copying machine. (7) Information recorded using a facsimile can be sent to a remote place in a short time.

FIG. 16 is a block diagram showing an example of the configuration of a confidential information recording / reproducing system for recording / reproducing confidential information by the method of the present invention described with reference to FIGS. 1, 4 and 7. is there. In the recording system denoted by reference numeral 100, 101 is a personal computer,
In addition to character information, confidential information composed of digital information such as voice information, image information, and computer programs is stored as binarized information, and public information is also stored as binarized information. ..

In the personal computer 101, the public information and the confidential information are combined using a predetermined encryption key by the method shown in FIGS. 1, 4, and 7, and converted into print data such as dot code. The printer 102 prints the public information in which the confidential information is embedded according to the print data on a sheet at a resolution of 400 dpi or higher. The print information obtained in this way is transferred to the copying machine 103.
Can be duplicated in bulk and can be sent by mail or by fax 104 to the desired party.

In the reproducing system indicated by reference numeral 200, the imaged information received by the facsimile apparatus 201 is input to the personal computer 202. The document sent by mail is read by the scanner 203 into dot patterns of the information printed on the paper, and the read dot pattern data is input to the personal computer 202.

The personal computer 202 separates and takes out the confidential information embedded in the public information using the restoration key corresponding to the encryption key used for the confidential information embedding process performed on the recording system 100 side. ,
If necessary, another confidential key is used to translate the separated confidential information to reproduce the confidential information.

The confidential information reproduced on the personal computer 202 is printed on the printer 204,
Documented. The reproduced confidential information may be displayed on a CRT display device (not shown) or may be output by voice using a speaker or the like (not shown).

FIG. 16 shows an encrypted information recording / reproducing system as an example of a system to which the method of the present invention is applied. The illustrated system has a configuration in which confidential information that cannot be leaked to a third party is embedded as information such as a dot pattern in public information imaged using an encryption key and decrypted using a restoration key. The embedded information may be printed on paper, or it may be computer-generated as image information.
It may be transferred to another computer on the network.

Examples of application of this system include electronic commerce, digital cash, prepaid
Examples include cards, approval documents, contract documents, resumes, and assessment sheets.

The components of this system are a personal computer having a word processor function, encrypted information recording software, a printer, a scanner, encrypted information reproducing software, LAN and WAN.

Another form of the system to which the method of the present invention is applied will be described below.

(A) Digital signature The character information is printed on the paper as human readable characters and at the same time, the information is converted into information such as a dot pattern on the paper using an encryption key (private key). Embed. Approver is the recovery key (public key)
The embedded information is solved using and compared with the character information to confirm that they are the same. The embedded information cannot be tampered with unless a third party obtains the encryption key (private key).

Examples of applications of this system include electronic commerce, digital cash, written approval, contract documents, identification documents, and the like.

The components of this system are a personal computer having a word processor function, encrypted information recording software, a printer, a scanner, and encrypted information reproducing software.

(B) FAX information compression / transfer device A plurality of pieces of character information are compressed and printed as dot codes on one sheet of paper, and then faxed. For one A4 sheet,
It is possible to send an amount of characters (thousands to 10,000 characters) that is several to ten times larger than usual. It can be applied to FAX transmission of business documents.

The components of this system are a personal computer having a word processor function, encrypted information recording software, a printer, and a G3-compatible FA with a resolution of 200 dpi.
X, encrypted information reproduction software.

(C) Multimedia Information Recording / Reproducing Device Multimedia information such as voice information, color image information, computer programs, etc. is embedded as character information or graphic information as dot pattern information. The embedded information is taken out and printed or reproduced on a CRT display device or the like.

As an application example of this system, a document in which a human voice is embedded (business instruction, correction of correspondence education, a letter for the blind), a document in which a color image is embedded (advertisement, manual), and program data are embedded. Documents (design drawings, NC machine programs) can be cited.

The components of this system are a microphone, a speaker, a still camera, a video device, a scanner, a personal computer also having a word processor function, encrypted information recording software, a printer, encrypted information reproducing software, and the like.

(D) Information Storage Medium System Character information, audio information, color image information, multimedia information such as computer programs are recorded on paper as information such as dot patterns. It is an information storage medium that has features such as ultra-low cost, easy handling, easy copying, transmission by FAX, and easy transportation.

As an application example of this system, business documents, computer programs, souvenir photographs, music, etc. can be stored and distributed.

The components of this system are a microphone, a speaker, a still camera, a video device, a scanner, a personal computer having a word processor function, encrypted information recording software, a printer, encrypted information reproducing software, and the like.

[0106]

The effects of the present invention are as follows. (1) A third party does not understand the existence of confidential information recorded on paper. (2) Even if a third party obtains the playback device, it is unlikely that the confidential information will be decrypted. (3) Since a large amount of confidential information is embedded, digital information such as character information, audio information, image information, and computer programs can be combined and recorded or reproduced on paper. (4) No special recording / reproducing device is required. (5) Because it is printed on paper and easy to copy,
It is possible to add, correct and delete confidential information by cutting and pasting. (6) A large number of copies can be made in a short time by using a copying machine. (7) Information recorded using a facsimile can be sent to a remote place in a short time.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method of creating a confidential information recording document for explaining an example of an embodiment of the present invention described in claim 1.

FIG. 2 is an enlarged view showing an example of a reference point mark used in the method for creating a confidential information recording document shown in the flowchart of FIG.

FIG. 3 is a diagram showing an example of a document created by the method for creating a confidential information recording document shown in the flowchart of FIG.

FIG. 4 is a flowchart showing a method of creating a confidential information recording document for explaining another example of the embodiment of the invention described in claim 1.

5 is a diagram showing an example of a document created by the confidential information recording document creating method shown in the flowchart of FIG.

FIG. 6 is an explanatory diagram showing an enlarged confidential information area for explaining embedding of a reference point mark and confidential information in public information in the case of the confidential information recording document creating method shown by the flowchart of FIG. 4;

FIG. 7 is a flowchart showing a method of creating a confidential information recording document for explaining another example of the embodiment of the invention described in claim 1.

8 is a diagram showing an example of a document created by the confidential information recording document creating method shown in the flowchart of FIG.

9 is an enlarged view of a confidential information area for explaining a state in which a reference point mark and confidential information are embedded in public information by the confidential information recording document creating method shown by the flowchart of FIG.

FIG. 10 is a flowchart showing a method of creating a confidential information recording document for explaining an example of the embodiment of the invention described in claim 2.

11 is a diagram showing an example of a document created by the confidential information recording document creating method shown in the flowchart of FIG.

FIG. 12 is a flowchart showing a method of creating a confidential information recording document for explaining another example of the embodiment of the invention described in claim 2.

FIG. 13 is a diagram for explaining a method of replacing color dot data when synthesizing information in units of confidential information blocks in FIG.

14 is a diagram showing an example of a document created by the confidential information recording document creating method shown in the flowchart of FIG.

15 is an enlarged view showing a state in which confidential information is embedded in public information by the confidential information recording document creating method shown by the flowchart in FIG.

FIG. 16 is a block diagram showing an example of a system configuration for recording and reproducing confidential information by the method of the present invention.

[Explanation of symbols]

(A), (b), (c) Blank area B1, B2, B3, BC1, BC2, BC3 Confidential information block F Paper G, GC Public information image J Number of confidential information blocks in large confidential information block K Unit bit Number L Number of repeated executions M0, MC0 Original mark M1, M2, M3, MC1, MC2, MC3 Mark R1, R2, R3, RC1, RC2, RC3 Reference point mark S Number of bits of one block of large confidential information block (J =
In the case of 1, it is the same as the number of bits of one block of the confidential information block) W Total number of bits of binarized confidential information X, Y, Z, XC, YC, ZC Confidential information area Z1, Z2, Z3, ZC1 , ZC2, ZC3 mark data

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Machida 3-23 Shimoshinmachi, Toyama City, Toyama Prefecture Inside Intec Co., Ltd.

Claims (2)

[Claims] 1. A confidential information recording method for recording confidential information on a print medium on which a public information image is printed, the method comprising: converting an image of the public information into dot public information data; Converting information into binarized confidential information data, obtaining dot data for recording the confidential information based on the binarized confidential information data, embedding position information of the dot data in the print medium, and Preparing data relating to the embedding method as encryption key information, embedding the dot data by substituting it into the dot-form publicized information data based on the encryption key information to obtain composite information, and printing data according to the composite information data. A step of creating, and an image according to the composite information data on the print medium according to the print data Confidential information recording method characterized by comprising the step of printing. 2. A confidential information recording method for recording confidential information on a print medium, the method comprising: converting required confidential information into binary confidential information data; and the confidential information based on the binary confidential information data. Obtaining dot data for recording, preparing dot original image data of an original image to be printed on a predetermined portion of the print medium, embedding position information and embedding of the dot data in the original image One or more including the confidential information by preparing the data related to the method as encryption key information, and repeating the process of embedding the dot data in the dot original image data according to the encryption key information as necessary. Creating transformed image data of the Data and the modified image data, and a step of printing the original image and the one or more modified images on the print medium, the confidential information recording method.