Patent Application
20070041608
1. Field of the Invention
The present invention relates to a technology whereby confidential information is added into a document image in a form other than text.
2. Description of the Related Art
There are technologies adopted in practical applications in recent years that allow various types of information to be included in a document by embedding black pixels (dots) in the background of the document with specific methods. Examples of such information include anti-copy information used to deter duplication of a document on a copier, density information with regard to a base dot matrix pattern used to draw a pattern in the background of the document (hereafter simply referred to as density information) and confidential information (also referred to as sensitive information or undisclosed information) generated as an electronic watermark, detectable with a specific type of detection device.
Anti-copy information is used in anti-copy technologies whereby a pattern drawn over the base dot matrix of a document in such a manner that it is not readily visible to the human eye emerges as a visually perceptible pattern when the document is duplicated on a copier due to the characteristics of the copier (see, for instance, Japanese Laid Open Patent Publication No. H2-29679). Density information generated by disposing dots with varying average density levels in the background of a document is used to draw a visible pattern. With confidential information (sensitive information or undisclosed information), a specific type of information can be detected by detecting with a detection device dots embedded in the background of a document in a specific pattern.
It may sometimes be desirable to simultaneously embed a plurality of types of information, such as those described above all in a single document. For instance, there is the need for a document with both anti-copy information and confidential information embedded together therein so as to deter duplication of the document containing the confidential information and a document having embedded therein both density information and confidential information so as to indicate the importance of the document carrying the confidential information. However, if a base dot matrix pattern for duplication deterrence or for pattern drawing is printed over the electronic watermark constituting the confidential information, the base dot matrix pattern becomes noise in the electronic watermark and the information embedded as the electronic watermark can no longer be extracted. In addition, if base dot matrix patterns with different cycles are simply superimposed, interference fringes may manifest.
An object of the present invention, which has been completed by addressing the problems of watermark information embedding apparatuses in the related art discussed above, is to provide a new and improved watermark information embedding apparatus, a new and improved image processing device, a new and improved watermark information embedding method and a new and improved image processing method, with which a plurality of types of information such as anti-copy information and confidential information or density information and confidential information can be embedded in the document together.
In order to achieve the object described above, the present invention provides a confidential information embedding apparatus that embeds confidential information in a document through electronic watermarking, comprising the following components.
It is to be noted that in place of the watermark image forming unit described above, the following components may be included.
The above described invention is characterized by the pattern table included therein. Namely, (1) a permanent dot pattern that remains after the document is copied and (2) a temporary dot pattern that is erased when the document is copied are both allocated to each of the symbols constituting the confidential information, and these dot patterns are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the anti-copy information used to determine whether the permanent dot pattern or the temporary dot pattern is set. In this manner, the anti-copy information and the confidential information can both be embedded in the document together so as to deter duplication of the document with the confidential information embedded therein.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
The permanent dot pattern may be, for instance, a pattern that includes dots concentrated in part of the dot pattern. The temporary dot pattern may be a pattern with black pixels uniformly dispersed in the dot pattern.
In order to achieve the object described above, the present invention provides a confidential information embedding apparatus that embeds confidential information in a document through electronic watermarking, comprising the following components.
It is to be noted that in place of the watermark image forming unit described above, the following components may be included.
The above described invention is characterized by the pattern table included therein. Namely, each of the symbols constituting the confidential information is allocated with the first density dot pattern and the second density dot pattern with varying density levels, which are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the density information used to determine whether the first density dot pattern or the second density dot pattern is to be set. Thus, the density information and the confidential information can be embedded together in the document. Since a pattern can be drawn in the background of the document based upon the density information, the importance of the document can be indicated and tampering with the document can be prevented.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
In order to achieve the object described above, the present invention provides a confidential information embedding apparatus that embeds confidential information in a document through electronic watermarking, comprising the following components.
It is to be noted that in place of the watermark image forming unit described above, the following components may be included.
The above described invention is characterized by the pattern table included therein. Namely, (1) a permanent dot pattern which remains after the document is copied and (2) a temporary dot pattern which is erased as the document is copied are both allocated to each of the symbols constituting the confidential information. The permanent dot pattern and the temporary dot pattern are each available as n types of dot patterns with varying density levels. These dot patterns are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the anti-copy information used to determine whether the permanent dot pattern or the temporary dot pattern is to be set and the density information used to determine the specific density level of the dot pattern among the n density levels. As a result, the anti-copy information, the density information and the confidential information can all be embedded in the document together. Duplication of the document containing the confidential information embedded therein is deterred and, at the same time, a pattern can be drawn in the background of the document based upon the density information to indicate the importance of the document and deter tampering on the document.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
The permanent dot pattern may be, for instance, a pattern that includes dots concentrated in part of the dot pattern. The temporary dot pattern may be a pattern with black pixels uniformly dispersed in the dot pattern.
In order to achieve the object described above, the present invention provides an image processing device, comprising a data input means for inputting document data with specific information added thereto and a pattern generating means for generating a machine-readable pattern based upon the specific information. The machine-readable pattern generated based upon the specific information includes a permanent dot pattern that remains after the document is copied and a temporary dot pattern that is erased as the document is copied.
In order to achieve the object described above, the present invention provides a confidential information embedding method for embedding confidential information in a document through electronic watermarking, comprising the following steps.
It is to be noted that the permanent dot pattern to remain even after the document is copied and the temporary dot pattern to be erased as the document is copied, both allocated to each of symbols constituting the confidential information, are managed in a pattern table.
The method described above may include the following steps in place of the watermark image forming step.
According to the above described invention, (1) a permanent dot pattern that remains after the document is copied and (2) a temporary dot pattern that is erased when the document is copied are both allocated to each of the symbols constituting the confidential information, and these dot patterns are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the anti-copy information used to determine whether the permanent dot pattern or the temporary dot pattern is set. In this manner, the anti-copy information and the confidential information can both be embedded in the document together so as to deter duplication of the document with the confidential information embedded therein.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
The permanent dot pattern may be, for instance, a pattern that includes dots concentrated in part of the dot pattern. The temporary dot pattern may be a pattern with black pixels uniformly dispersed in the dot pattern.
In order to achieve the object described above, the present invention provides a confidential information embedding method for embedding confidential information in a document through electronic watermarking, comprising the following steps.
It is to be noted that the first density dot pattern and the second density dot pattern with varying density levels both allocated to each of the symbols constituting the confidential information, are managed in a pattern table.
The method described above may include the following steps in place of the watermark image forming step.
According to the above described invention, each of the symbols constituting the confidential information is allocated with the first density dot pattern and the second density dot pattern with varying density levels, which are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the density information used to determine whether the first density dot pattern or the second density dot pattern is to be set. Thus, the density information and the confidential information can be embedded together in the document. Since a pattern can be drawn in the background of the document based upon the density information, the importance of the document can be indicated and tampering with the document can be deterred.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
In order to achieve the object described above, the present invention provides a confidential information embedding method for embedding confidential information in a document through electronic watermarking, comprising the following steps.
It is to be noted that the n types of permanent dot patterns with varying density levels to remain even after the document is copied and the n types of temporary dot patterns with varying density levels to be erased as the document is copied, allocated to each of symbols constituting the confidential information, are managed in a pattern table.
The method described above may include the following steps in place of the watermark image forming step.
According to the above described invention (1) a permanent dot pattern which remains after the document is copied and (2) a temporary dot pattern which is erased as the document is copied are both allocated to each of the symbols constituting the confidential information. The permanent dot pattern and the temporary dot pattern are each available as n types of dot patterns with varying density levels. These dot patterns are classified and managed as hyper-complex matrices in the pattern table. The watermark image is formed based upon the anti-copy information used to determine whether the permanent dot pattern or the temporary dot pattern is to be set and the density information used to determine the specific density level of the dot pattern among the n density levels. As a result, the anti-copy information, the density information and the confidential information can all be embedded in the document together. Duplication of the document containing the confidential information embedded therein is deterred and, at the same time, a pattern can be drawn in the background of the document based upon the density information to indicate the importance of the document and deter tampering on the document.
The permanent dot pattern and the temporary dot pattern are patterns of dots arranged along varying wave directions and/or in varying dot arrays. The confidential information may be provided by assigning a dot pattern to each symbol and disposing such dot patterns in a specific combination. Through the use of such dot patterns, dots can be disposed substantially uniformly in the background of the document so that a third-party cannot readily perceive the presence of the anti-copy information and the confidential information embedded in the document.
The permanent dot pattern may be, for instance, a pattern that includes dots concentrated in part of the dot pattern. The temporary dot pattern may be a pattern with black pixels uniformly dispersed in the dot pattern.
In order to achieve the object described above, the present invention provides an image processing method comprising a data input step in which document data having specific information added thereto are input and a pattern generating step in which a machine-readable pattern is generated based upon the specific information. The machine-readable pattern generated based upon the specific information includes a permanent dot pattern to remain even after the document is copied and a temporary dot pattern to be erased as the document is copied.
As explained above, the present invention allows various types of information to be embedded in a document together. More specifically, anti-copy information used to deter duplication of the document on a copier are and confidential information provided as an electronic watermark detectable with a specific type of detection device can be embedded together in the document, or density information with regard to a base dot matrix pattern used to draw a pattern in the background of the document and confidential information can be embedded together in the document.
The following is a detailed explanation of the preferred embodiments of the watermark information embedding apparatus, the image processing device, the watermark information embedding method and the image processing method according to the present invention, given in reference to the attached drawings. It is to be noted that in the specification and the drawings, the same reference numerals are assigned to components having substantially identical functions and structural features to preclude the necessity for a repeated explanation thereof.
In the following embodiment, an electronic watermarking technology is adopted to embed anti-copy information together with confidential information.
The watermark information embedding apparatus 10 creates a document image based upon document data and confidential information to be embedded in the document and prints out the document image onto a paper medium. The watermark information embedding apparatus 10 comprises a document image forming unit 11, a watermark image forming unit 12, a watermarked document image composition unit 13 and an output device 14, as shown in
The document image forming unit 11 generates a document image based upon the document data 15 in correspondence to each page. The document image forming unit 11 generates a print preview image of the document data 15. More specifically, a white pixel area in the document image corresponds to a portion of the paper where nothing is printed, whereas a black pixel area in the document image corresponds to a portion of the paper on which black ink is applied. It is to be noted that while an explanation is given in reference to the embodiment by assuming that the document data are printed with black ink (a single color) on a white paper surface, the present invention is not limited to this example and it may be adopted with equal effectiveness when printing the document data in color (multiple colors).
The watermark image forming unit 12 forms a watermark image by obtaining a dot pattern from a pattern table 19 based upon the confidential information 16 and anti-copy information 17. The confidential information 16, the anti-copy information 17 and the pattern table 19 are explained in detail below.
The confidential information 16 is first explained.
The confidential information 16 is handled by first encrypting a character string or the like representing specific confidential information as necessary and then digitizing the encrypted character string or the like to obtain N-complex coded data (N is any natural number equal to or greater than 2. The explanation of the embodiment is given by assuming, for simplification, that N=2.) Each coded symbol is made to correspond to a dot pattern prepared in advance. A dot pattern is created by arranging dots within a rectangular area of an arbitrary size to indicate a wave running along a given direction with a given wavelength, and a symbol is made to correspond to the specific wave direction or the specific wavelength. A watermark image contains such dot patterns disposed on an image with a given regularity.
Next, the anti-copy information 17 is explained. There is a technology known as an “anti-copy base dot matrix” whereby a pattern drawn over the base dot matrix of a document in such a manner that it cannot be easily perceived by the human eye emerges as the document is duplicated on a copier as a pattern visible to the human eye due to the characteristics of the copier. This technology is realized by disposing as tiles a plurality of types of dot patterns with average density levels thereof close to each other in the background of the document, as shown in
For instance, if the permanent dot pattern and the temporary dot pattern are each to be formed over an 8×8 pixel area, the permanent dot pattern may be formed to include black pixels concentrated over an area of the pattern and the temporary dot pattern may be formed to include black pixels uniformly dispersed in the pattern. It is to be noted that the shapes and the density levels of the permanent dot pattern and the temporary dot pattern can be adjusted in conformance to the characteristics of the target copier at which duplication needs to be deterred, the characteristics of the printer to be used to print out the document containing embedded information or the like.
The anti-copy information 17 is used to determine whether the permanent dot pattern (cpy=0) or the temporary dot pattern (cpy=1) is to be set depending upon the position in the watermark image. This determination may be made by, for instance, using a binary image so as to select the temporary dot pattern over an area corresponding to pixels indicating 1 and select the permanent dot pattern for an area corresponding to pixels indicating 0. Since the temporary dot pattern and the permanent dot pattern are adjusted in correspondence to the specific copier or the printer in use, as described above, a plurality of sets of permanent dot patterns and temporary dot patterns may be prepared in advance, each set in correspondence to a specific target printer or copier, and one set of dot patterns may be selected and used at a given location.
By combining a plurality of sets of anti-copy information 17 in an arbitrary manner, any of various marks can be made to emerge in the copied document. For instance, text such as “copy” indicating that the document is a duplicate, “void” indicating that the document is not a valid document, “not for use” indicating that the use of the document is disallowed or the like, or a mark (e.g., X enclosed in a circle) with a similar meaning may be made to emerge in the duplicated document.
Next, the pattern table 19 is explained. The pattern table 19 achieved in the embodiment is used to manage in a table the permanent dot pattern which is to remain even after the document is copied and the temporary dot pattern which is to be erased when the document is copied, both allocated to each of the symbols constituting the confidential information 16. Namely, the pattern table 19 contains patterns, the number of which is equal to the value obtained by multiplying the number of different types of patterns constituting the anti-copy information 17 (two types, the permanent dot pattern and the temporary dot pattern) by the number of symbols constituting the confidential information 16. There will be 4 (=22) different types of symbols constituting the confidential information if a single pattern is used to record two-bit data, whereas there will be 2 (=21) symbols constituting the confidential information if a single pattern is used to record one-bit data. A pattern is output from the pattern table 19 in conformance to a specified anti-copy information type and a specified symbol type of confidential information.
A pattern can be output from this pattern table 19 in conformance to a specified anti-copy information type (cpy=0 or 1) and a specific type of symbol constituting the confidential information (inf=0˜3). The following is an explanation of the different anti-copy information types and different types of symbols constituting the confidential information.
First, the different types of anti-copy information (cpy=0, 1) are explained.
There are two types of anti-copy information, i.e., the permanent dot pattern (cpy=0) and the temporary dot pattern (cpy=1). The permanent dot pattern (cpy=0) includes a relatively large spot expressed by using four to six dots. While the duplication capability of a given copier is a critical factor, this point, in principle, remains visible even after the document is duplicated on the copier. These relatively large points are set so as to minimize interference with the frequency component of the pattern used to record the electronic watermark signal and to amplify the signal in some cases. The temporary dot pattern (cpy=1) includes uniformly dispersed dots and is erased when the document is duplicated on the copier.
Next, the different types of symbols (inf=1, 2, 3) constituting the confidential information are explained.
The type of the specific symbol constituting the confidential information is recorded over the oval area on each pattern in
In
Likewise, dots are set close to each other along the direction of arctan (−3) relative to the horizontal axis, with the direction along which the wave is propagated expressed as arctan (⅓) in
In
In
While the permanent dot patterns and the temporary dot patterns in the example presented in
In addition, while a single dot pattern may be allocated in correspondence to one set of information (anti-copy information and confidential information) as shown in
Specific details of the confidential information 16, the anti-copy information 17 and the pattern table 19 input to the watermark image forming unit 12 are as explained above. Based upon the confidential information 16 and the anti-copy information 17, the watermark image forming unit 12 obtains dot patterns from the pattern table 19 and forms a watermark image. The image thus obtained assumes an overall pattern that allows an area over which the permanent bit pattern as selected based upon the anti-copy information to emerge as a visible image portion in a duplicate and allows specified data to be retrieved from an embedded information bit string when verifying the watermark.
The watermarked document image composition unit 13 creates a watermarked document image by superimposing the document image and the watermark image one on top of the other. In addition, the output device 14, which may be a printer or the like, prints out the watermarked document image onto a paper medium. The document image forming unit 11, the watermark image forming unit 12 and the watermarked document image composition unit 13 described so far may be realized as a function in the printer driver.
A printed document 20, printed out by embedding the confidential information 16 in the initial document data 15, is saved and managed physically. In the printed document 20, the anti-copy information and the confidential information are embedded together.
As described above, the embodiment makes it possible to embed anti-copy information and confidential information together in a printed document so as to deter duplication of the document containing the confidential information embedded therein. The anti-copy information does not pose any difficulty in reading the confidential information.
The embodiment is characterized in that density information with regard to a watermark dot matrix array (hereafter simply referred to as density information) and confidential information are embedded together in a document by adopting electronic watermarking technology.
In the embodiment, density information 18 is input to the watermark image forming unit 12. Accordingly, dot patterns corresponding to the density information 18 are stored as a table in the pattern table 19. Since all the other features of the embodiment are substantially identical to those of the first embodiment, a repeated explanation thereof is omitted and the density information 18 and the pattern table 19 are described in detail below.
The density information 18 is used to draw a pattern in the background of the document. Any type of graphic drawn in the background of the document may be regarded as congregations of dots. Such drawings can be captured as binary (multi-valued) bit string data conversion executed by using a predetermined threshold value. This means that a pattern can be drawn in the background of the document by using two-dimensional (n dimensional) bit string information. The density information 18 is two-dimensional (n dimensional) bit string information used to draw a pattern in the background of the document.
The pattern table 19 is used to manage in a table a first density dot pattern (density pattern=0) and a second density dot pattern (density pattern=1) with varying density levels, which are allocated to each of the symbols constituting the confidential information. Namely, in the pattern table 19, patterns, the number of which is equal to a value calculated by multiplying the number of different types of density information 18 (2, i.e., the first density dot pattern and the second density dot pattern) by the number of symbols constituting the confidential information 16. There will be 4 (=22) different types of symbols constituting the confidential information if, for instance, a single pattern is used to record two-bit data, and there will be 2 (=21) different types of symbols constituting the confidential information if a single pattern is used to record one-bit data. A given pattern corresponding to a specified density information type and a specified type of confidential information symbol is output from the pattern table 19.
As the density information type (density pattern=0 or 1) and the confidential information symbol type (inf=0˜3) are specified, a single corresponding pattern is output from the pattern table 19. It is to be noted that while there are two density pattern types in the example presented in
The average density levels of the individual density pattern types are different from each other. The density levels of the density patterns 0 are relatively low and the density levels of the density patterns 1 are relatively high in
The confidential information symbol types (inf=0˜3) are similar to those in the first embodiment and the type of the specific symbol constituting the confidential information is recorded over the oval area on each pattern in
As explained above, the embodiment allows both density information and confidential information to be embedded in a document together. Since a pattern can be drawn in the background of the document based upon the density information, the importance of the document can be indicated and tampering on the document can be deterred. The density information does not pose any difficulty in reading the confidential information.
The embodiment is characterized in that anti-copy information, density information and confidential information are all embedded together in a document by adopting an electronic watermarking technology.
In the embodiment, anti-copy information 17 and density information 18 are input to the watermark image forming unit 12. Accordingly, dot patterns corresponding to the anti-copy information and the density information are stored in the pattern table 19 as a table. Since the other features of the embodiment are substantially identical to those of the first embodiment, a repeated explanation thereof is omitted, and the pattern table 19 is explained in detail.
n (n is a natural number equal to or greater than 2 and n=3 in the embodiment) types of permanent dot patterns with varying density levels, which are to remain even after the document is accompanied, and n types of temporary dot patterns with varying density levels, which are to be erased when the document is copied, are allocated to each of the symbols constituting the confidential information and are managed in a table at the pattern table 19 achieved in the embodiment. Namely, the pattern table 19 contains patterns, the number of which equals a value obtained by multiplying the number of different types of anti-copy information 17 (2, i.e., the permanent dot pattern and the temporary dot pattern) by the number of different types of density information 18 (3, density=0, 1, 2) and then by multiplying the product by the number of symbols constituting the confidential information 16. There will be four (=22) different types of symbols constituting the confidential information 16 if, for instance, a single pattern is used to record two-bit data, and there will be 2 (21) different types of symbols if a single pattern is used to record one-bit data. A given pattern corresponding to a specified anti-copy information type, a specified density information type and a specified confidential information symbol type is output from the pattern table 19.
As the anti-copy information type (either cpy=0 or cpy=1), the density information type (one of the three density types, 0, 1, 2) and the information symbol type (inf=0˜3) are specified, a single corresponding pattern is output from the table.
As described above, the embodiment allows anti-copy information, density information and confidential information to be embedded together in a document. Thus, duplication of the document containing the confidential information embedded therein can be deterred and, at the same time, a pattern can be drawn in the background of the document based upon the density information to indicate the importance of the document and deter tampering on the document. The anti-copy information and the density information do not pose any difficulty in reading the confidential information.
While the invention has been particularly shown and described with respect to preferred embodiments of the watermark information embedding apparatus, the image processing device, the watermark information embedding method and the image processing method according to the present invention by referring to the attached drawings, the present invention is not limited to these examples and it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit, scope and teaching of the invention.
For instance, either of the temporary dot pattern or the permanent dot pattern in the anti-copy base dot matrix may be formed as a pattern which does not include any electronic watermark signal. In such a case, information with redundancy generated by using error correction codes or the like should be embedded.
As described above, the present invention makes it possible to embed a plurality of different types of information together in a document. More specifically, anti-copy information for deterring duplication of the document on a copier and confidential information generated as an electronic watermark that can be detected with a specific type of detection device can be embedded together in the document, or density information with regard to a base dot matrix pattern used to draw a pattern in the background of the document can be embedded together with confidential information in the document.
The present invention may be adopted in a technology for adding confidential information in a document image in a form other than text and, in particular, it may be adopted in a watermark information embedding apparatus, an image processing device, a watermark information embedding method and an image processing method that allow confidential information to be added into a document image in a form other than text.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-150803 | May 2003 | JP | national |
This application is entitled to the benefit of PCT International Application No.PCT/JP2004/006732, filed on May 19, 2004, which claimed priority of Japanese Patent Application No.JP2003-150803, filed on May 28, 2003.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/06732 | 5/19/2004 | WO | 11/3/2005 |
