KR101568211B1 - System and method for hiding and extracting reversible data - Google Patents

Abstract

When extracting reversible information from an information concealment document file in which concealment information data is encoded in a document file already compressed, a predetermined restoration format is applied to decode the information concealment document file in units of a predetermined length of a bit block, A plurality of characters included in the information are analyzed on the basis of a predetermined information analysis criterion, and an information index including at least one of a significant index, a no-good index and a document index is calculated according to a result of the analysis, Extracts the hidden information bits hidden in the bit block based on the comparison result of the exponential threshold value, converts the bit value before decoding based on the value of the secret information bit for each bit block, Decodes it into a restoration format and restores it to the original document file.

Description

[0001] SYSTEM AND METHOD FOR HIDING AND EXTRACTING REVERSIBLE DATA [0002]

The present invention relates to a system and method for reversibly concealing information data in a compressed document file and extracting concealed information data on the compressed document.

As more information is stored in digital form, various information protection techniques are being developed to protect digital media that can be easily copied or changed.

Among them, information hiding is widely used to ensure confidentiality with encryption. Such an information concealment technique can insert data into a digital medium by changing the digital medium.

In this regard, Korean Patent Laid-Open No. 10-2007-0076130 (entitled " Inserting and Extracting Information for Document Authentication ") discloses a method for extracting and extracting information, The present invention relates to a lossless data embedding method in which an image is divided into a plurality of blocks, each divided block is divided into sub-blocks, authentication information is inserted into one of the divided sub-blocks, Discloses a technique of inserting authentication information (binary information) into a pixel having a minimum pixel value among blocks.

However, when a document is compressed, a random number level output is generated. Therefore, there is a limit in that it is not easy to conceal information reversibly to a compressed document other than an original document.

An embodiment of the present invention is to solve the problems of the prior art described above, and it is an object of the present invention to provide an information concealment apparatus and method for encoding concealed information data in addition to an already compressed document file, And a method for extracting information.

It should be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may exist.

According to an aspect of the present invention, there is provided a reversible information concealment apparatus comprising: a document compression unit that encodes an original document file into a predetermined compression format to output a compressed document file; Dividing the bit stream of the compressed document file into a plurality of bit blocks each having a predetermined first length and dividing the predetermined hidden information data into a plurality of hidden information bits each having a predetermined second length, And an information concealment unit for converting the bit values of the bit block based on the value of the allocated secret information bits; And an information hiding document providing unit for providing an information hiding document file including the bit blocks obtained by converting the bit values.

According to another aspect of the present invention, there is provided a reversible information extraction apparatus comprising: a compressed document input unit receiving an information hiding document file in which hidden information data is encoded in a compressed document file; A restoration preprocessing unit for decoding the information hiding document file in units of a predetermined length by applying a preset restoration format; An information analysis unit for analyzing a plurality of characters included in the decoded bit block based on a predetermined information analysis criterion and calculating an information index including at least one of a significance index, part; Extracting a hidden information bit hidden in the bit block based on a result of comparing the calculated information index and a predetermined information index threshold value, and comparing the bit value before decoding with the value of the hidden information bit for each bit block, A concealed information extracting unit for converting the concealed information based on the concealed information; And a document decompression unit decoding the bit block into which the bit value has been converted through the secret information extracting unit into the restoration format and restoring the same into an original document file.

According to another aspect of the present invention, a method for concealing information in a precompressed document file includes the steps of: (a) encoding an original document file in a predetermined compression format to output a compressed document file; (b) dividing the bit stream of the compressed document file into a plurality of bit blocks each having a predetermined first length; (c) allocating a plurality of concealment information bits obtained by dividing predetermined concealment information data by a predetermined second length unit to the plurality of bit blocks; (d) converting a bit value of the bit block based on the value of the allocated secret information bit; And (e) providing an information hiding document file including bit blocks obtained by converting the bit values.

A method for extracting secret information data hidden in an information hiding document file according to another aspect of the present invention includes the steps of (a) receiving the information hiding document file in which secret information data is encoded in a compressed document file step; (b) decoding the information hiding document file in units of a predetermined length by applying a preset restoration format; (c) analyzing a plurality of characters included in the decoded bit block based on a predetermined information analysis criterion, and calculating an information index including at least one of a significance index, a meaningless index, and a document index according to the analyzed result ; (d) extracting the hidden information bits hidden in the bit block based on a result of comparing the calculated information index with a preset information index threshold value; (e) converting the bit value before decoding according to the value of the secret information bit for each bit block; And (f) decoding the bit block in which the bit value has been converted into the restoration format and restoring the decoded bit block into an original document file.

According to the above-mentioned object of the present invention, it is possible to further encode the secret information data without data loss of the document file in the precompressed state through the reversible encoding technique which can completely restore the data without modifying the original data .

Further, according to any one of the tasks of the present invention, a document file in which secret information data is additionally encoded on a compressed document file is decoded based on an information index calculated according to the attribute of characters included in each bit block, The decoding result can be obtained.

1 is a block diagram illustrating a configuration of a reversible information concealment system according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of a reversible information concealment apparatus according to an embodiment of the present invention.
3 is a diagram for explaining a bitstream structure of a compressed document file according to an embodiment of the present invention.
FIG. 4 illustrates an example of a character included in a bit block of a document file according to an exemplary embodiment of the present invention. Referring to FIG.
5 is a flowchart illustrating a reversible information concealment method according to an embodiment of the present invention.
6 is a block diagram illustrating a configuration of a reversible information extraction apparatus according to an embodiment of the present invention.
7 is an ASCII code table for explaining a method of calculating an information index according to an embodiment of the present invention.
8 is a flowchart for explaining a reversible information extraction method according to an embodiment of the present invention.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

1 is a block diagram illustrating a configuration of a reversible information concealment system according to an embodiment of the present invention.

1, the reversible information concealment system 10 according to an embodiment of the present invention includes a reversible information concealment apparatus 100 and a reversible information extraction apparatus 200. As shown in FIG.

More specifically, reversible information hiding apparatus 100 is secret information data (b _k) the hidden secondary processing the encoding, and the information according to the result of the second encoding of the set compression document (X _k) with a compressed format primary encoding And outputs a concealed document (Y _k ).

Reversible information extraction device 200 extracts the secret information data (b _k) from receiving the information hiding document (Y _k) supplied from the reversible information hiding apparatus 100, information hiding document (Y _k) compressing the document (X _k . Then, the reversible information extracting apparatus 200 decodes the compressed document X _k based on the extracted secret information data b _k to restore the original document.

Hereinafter, the configuration and operation of the reversible information concealment apparatus according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5. FIG.

2 is a block diagram illustrating a configuration of a reversible information concealment apparatus according to an embodiment of the present invention.

2, the reversible information concealment apparatus 100 according to an exemplary embodiment of the present invention includes a document compression unit 110, an information concealment processing unit 120, an information concealment document providing unit 130, (140).

The document compressing unit 110 encodes the original document file into a predetermined compression format (hereinafter, referred to as 'primary encoding') and outputs a compressed document file.

The information concealment processing unit 120 converts the bit stream of the compressed document file output from the document compressing unit 110 into a plurality of bit blocks, and allocates and conceals secret information data to each bit block.

Specifically, the information concealment processing unit 120 divides the bit stream of the compressed document file into a plurality of bit blocks each having a predetermined length (hereinafter referred to as "L"). For information, the information concealment processing unit 120 extracts the length information of the bit block (i.e., 'L') through the information hiding document providing unit 130 for the hidden information extracting process of the reversible information extracting apparatus 200, ). ≪ / RTI >

The information concealment processing unit 120 generates a plurality of concealment information bits by dividing the bit stream of the previously set concealment information data in units of bits of a predetermined length (i.e., bit digits). At this time, the information concealment processing unit 120 may divide the secret information data into one-bit bit units or two-bit or more bit units.

For example, FIG. 3 illustrates a bitstream structure of a compressed document file according to an embodiment of the present invention.

3, the bit stream of the compressed document file is composed of a header and a payload, and the information concealment processing unit 120 converts the bit stream of the payload excluding the header of the compressed document file into a bit stream of a predetermined length ( That is, L) to divide the plurality of bit blocks X _k . At this time, the information concealment processing unit 120 can set the length of the bit block based on the size of the secret information data to be concealed. That is, the information concealment processing unit 120 may divide the bitstream of the compressed document file into a number of bit blocks corresponding to the number of hidden information bits.

The information concealment processing unit 120 allocates secret information bits for each bit block and encodes (hereinafter referred to as " secondary encoding ") which transforms the bit values of the corresponding bit block according to the value of the allocated secret information bits .

Specifically, when the secret information bits of one bit unit are allocated to each bit block, the information concealment processing unit 120 maintains or inverts the bit values of the bit block in units of one bit according to the value of the corresponding secret information bit.

For example, the information concealment processing unit 120 applies the operation according to Equation (1) to each bit block of the payload of the compressed document file to conceal the information.

&Quot; (1) "

That is, when the value of the secret information bit is '0' which is one-digit bit, the bit of the bit block X _k is maintained as it is. On the other hand, when the value of the secret information bit is '1' which is one-digit bit, the bit of the bit block X _k is inverted in units of 1 bit and output. For reference, the value of the secret information bit for holding or inverting the bit value of the bit block can be mutually changed.

In addition, the information concealment processing unit 120 may conceal the bit information of two or more digits of bits in each bit block.

Specifically, the information concealment processing unit 120 generates a plurality of random bit streams having lengths corresponding to the lengths of the bit blocks, and matches different random bit streams according to the values of the allocated secret information bits. Then, the information concealment processing unit 120 performs an exclusive OR (XOR) (or XOR operation) on the random bit stream matched with the allocated secret information bits and the corresponding bit block in units of one bit to perform the secondary encoding do.

For example, when the secret information bit is a two-bit bit, the information concealment processing unit 120 transforms the bit value of each bit block according to a matched random bit stream for each bit value using the following equation (2).

&Quot; (2) "

That is, the value of the secret information bits (b _k) of the two-digit bit in the case of '002, the random number bit stream, and the "R _0" matching, bit block (X _k) and the random number bit stream, each digit of the (R ₀₎ XOR (or " NXOR ") operation of the bit to output the bit block whose information is concealed. In this way, when K different random numbers are used as a random number bit stream, the secret information bits of 'log ₂ K' can be concealed for each bit block.

When the two or more secret information bits are concealed in the bit block, the information concealment processing unit 120 extracts the concealment information of the reversible information extraction device 200 from the information hiding document providing unit 130, And further provide a matched random bitstream for each value of each hidden information bit.

3, when a bit stream of a compressed document file is divided by a predetermined length L, a bit block having a length smaller than L may remain. That is, in FIG. 3, the compressed document file is divided into n number of bit blocks (i.e., X ₁ to X _n ), and the length of the last bit block (i.e., X _n ) is M smaller than L. At this time, the information concealment processing unit 120 may allocate the secret information bits to the bit blocks excluding the remaining bits less than a predetermined length (i.e., L) for the bit block.

The information hiding document providing unit 130 provides the information hiding document file including the secondarily encoded (i.e., bit-converted) bit blocks to the reversible information extracting apparatus 200.

On the other hand, in order for the reversible information extraction apparatus 200 to be described below to successfully extract the hidden information data hidden in the information hiding document file and to restore the original document file, a plurality of The information index calculated by analyzing the attribute of 'character' is needed. For reference, in one embodiment of the present invention, 'character' means all symbol systems for communication such as letters, numbers, symbols, and control characters.

To this end, the reversible information concealment apparatus 100 according to an embodiment of the present invention includes an information index threshold value setting unit 140.

The information index threshold setting unit 140 divides the bit stream of the original document file into a plurality of bit blocks having a predetermined size and calculates a predetermined information index for the characters corresponding to the bit values of the respective bit blocks. In one embodiment of the present invention, the predetermined information index includes a significance index, a meaningless index, and a document index. Then, the information index threshold setting unit 140 sets the calculated information index as an information index threshold value.

The information index threshold setting unit 140 provides the information index threshold value to the reversible information concealment extracting apparatus 200 through the information concealment document providing unit 130. [

Specifically, FIG. 4 illustrates an example of a character included in a bit block of a document file according to an exemplary embodiment of the present invention.

FIG. 4A shows a case where significant characters are included in a bit block of a document file. Assuming that the characters shown in FIG. 4A are the characters included in the bit block of the original document file, the information index threshold setting unit 140 sets the information index threshold value to the word and the And calculates a significance index threshold value based on the set information analysis criterion. At this time, the predetermined information analysis criterion can be obtained from a database in which existing words are stored as dictionary data. For reference, the information index threshold setting unit 140 may include a dictionary database by itself or may apply an information analysis standard using an external dictionary database.

On the other hand, FIG. 4B shows a case where meaningless characters are included in a bit block of a document file. Assuming that the characters shown in FIG. 4B are the characters included in the bit block of the original document file, the information index threshold setting unit 140 sets the information index threshold value setting unit 140 to set the character attributes of the corresponding bit block, An uncertainty index threshold value and a document index threshold value can be set based on the criterion. At this time, the predetermined information analysis standard is set as computer standard code data such as ASCII code and UNICODE.

As described above, the information index threshold setting unit 140 analyzes the attributes of the characters included in the bit blocks of the original document file based on predetermined information analysis criteria, and outputs the significance index threshold value, the no- And a document index threshold value.

On the other hand, the information index threshold value setting unit 140 calculates the information index threshold value based on the original document file by using the reversible information extraction apparatus 200 to process each bit block of the information hiding document file Correspond to the information index calculation method. Therefore, for convenience of description, a detailed description of the method of calculating the information index threshold value by the information index threshold value setting unit 140 will be omitted.

Hereinafter, a reversible information concealment method according to an embodiment of the present invention will be described in detail with reference to FIG.

5 is a flowchart illustrating a reversible information concealment method according to an embodiment of the present invention.

First, an original document file is encoded in a predetermined compression format to output a compressed document file (S510).

Then, the bit stream of the compressed document file is divided into a plurality of bit blocks each having a predetermined length (S520).

Then, a plurality of hidden information bits obtained by dividing the predetermined secret information data by a predetermined length unit are allocated to the plurality of bit blocks (S530).

Then, the bit value of the corresponding bit block is converted based on the value of the allocated secret information bit (S540).

More specifically, in the step S540, when the hidden information bit is assigned, the bit value of the corresponding bit block may be maintained or reversed in units of one bit according to the value of the hidden information bit.

In the step S540, when a secret information bit of at least two digits is allocated, a bit value of the bit block may be transformed by applying a random bit stream matched to each secret information bit value. At this time, a plurality of random bitstreams having a length corresponding to the length of the bit block are generated, and the random bitstreams are matched with each other according to the values of the allocated secret information bits. And performs the exclusive OR (XOR) or exclusive NOR (XNOR) operation on the corresponding bit block in units of one bit.

Next, the information hiding document file including the bit blocks obtained by converting the bit values is provided to the reversible information extracting apparatus (S550).

At this time, in step S550, the reversible information extracting apparatus 200 may further provide information on a random bit stream matched according to the value of the secret information bit and information of a predetermined length to the bit block.

In step S520, the bit stream of the payload excluding the header of the compressed document file is divided into the plurality of bit blocks. Accordingly, in steps S530 and S540, Lt; / RTI >

Also, before the step S550, the bit stream of the original document file is divided into a plurality of bit blocks each having a predetermined size, and at least one of a significance index, a no- And a step of calculating an information index threshold value. At this time, in step S550, the reversible information extraction apparatus 200 may further provide an information index threshold value.

Hereinafter, the configuration and operation of the reversible information extraction apparatus 200 according to an embodiment of the present invention will be described in detail with reference to FIGS. 6 to 8. FIG.

6 is a block diagram illustrating a configuration of a reversible information extraction apparatus according to an embodiment of the present invention.

6, the reversible information extraction apparatus 200 according to an embodiment of the present invention includes a compressed document input unit 210, a restoration preprocessing unit 220, an information analysis unit 230, an information analysis reference database 231 A concealment information extracting unit 240, and a document restoring unit 250.

The compressed document input unit 210 receives the information concealment document file in which the confidential information data is encoded in the compressed document file from the reversible information concealment apparatus 100. [

At this time, the compressed document input unit 210 may further receive the information index threshold value and the length information for the bit block unit, which are set based on the information index per bit block of the original document file, from the reversible information concealment apparatus 100.

The restoration preprocessing unit 220 decodes the information hiding document file into a predetermined restoration format, and decodes the information hiding document file in units of a bit block of a predetermined length (i.e., 'L') (hereinafter referred to as 'primary decoding'). At this time, the predetermined restoration format is a format corresponding to the compression format used by the reversible information concealment apparatus 100 for compressing the original document file.

The information analyzer 230 calculates the information index based on the characters included in the first decoded bit block and predetermined information analysis criteria. For reference, the information index is a value according to a set property of a character or a character included in a bit block, and includes a significance index, a meaningless index, and a document index.

Specifically, the information analyzing unit 230 uses the 'dictionary' data as an information analysis criterion to identify words included in 'dictionaries' (hereinafter, referred to as' Quot; significant word "). At this time, the information analysis unit 230 may use the dictionary data previously stored in the information analysis reference database 231, or may acquire and use the information analysis standard from the external dictionary database. In addition, the information analysis unit 230 can distinguish words based on spaces from the characters of the bit block. That is, at least one character positioned between two spaces among the characters of the bit block is determined as a word.

Then, the information analyzing unit 230 calculates a significance index based on the number of extracted meaning words. For example, the information analysis unit 230 may divide the number of significant words included in the 'dictionary' among the words included in the character of the corresponding bit block by the total number of words included in the characters of the bit block, Can be calculated.

Also, the information analyzing unit 230 calculates the nonsensitivity index and the document index according to the attribute of each character of the first decoded bit block using the 'computer standard code' as an information analysis standard. At this time, the information analyzing unit 230 extracts a computer standard code corresponding to each character included in the corresponding bit block, and based on the number of characters corresponding to the predetermined code among the extracted computer standard codes, Can be calculated.

For reference, the information analysis unit 230 may use a computer standard code table stored in the information analysis standard database 231 or may acquire an information analysis standard from an external computer standard code database. In addition, the computer standard codes can be classified into a letter code, a numeric code, a code code, and a control code according to character attributes.

Specifically, FIG. 7 is an ASCII code table for explaining a method of calculating an information index of a document file in an embodiment of the present invention.

ASCII CODE is an ASCII code that is used to represent all characters represented on the keyboard (eg, 'letters' such as' A, a, B, b, C, Quot; and " control " characters, such as " number ", " @, #, According to the ASCII code table of FIG. 7, code numbers '65' to '90' signify uppercase alphabetic characters, and code numbers '97' to '122' signify lowercase alphabetic characters. Such a set of character codes is referred to as 'ASCII-A'. In addition, the code numbers '48' to '57' mean 'number', and this numeric code set is referred to as 'ASCII-N'. In addition, code numbers '32' to '126' mean 'code', and this code code set is referred to as 'ASCII-S'. The code numbers 'I0' to '31' and the code number '127' represent control characters, and the control code set is referred to as 'ASCII-C'.

At this time, the information analyzing unit 230 may extract the corresponding ASCII code for each character included in the corresponding bit block, and calculate the nonsense index according to the number of characters corresponding to ASCII-C among the extracted ASCII codes.

On the other hand, in general, a character corresponding to ASCII-C (hereinafter referred to as an 'ASCII-C character') is not found in a general document file (hereinafter referred to as a ' ASCII-C characters such as ASCII code number '13' (i.e., 'CR') are used in a special document (hereinafter referred to as a specific document file).

Accordingly, the information analyzing unit 230 extracts a corresponding ASCII code for each character included in the corresponding bit block, extracts the number of ASCII-C characters and ASCII-S characters, ASCII-A characters, and ASCII- The document index is calculated based on the relationship between the number of N characters. For example, the information analysis unit 230 may calculate a value obtained by dividing the number of ASCII-C characters and ASCII-S characters by the number of ASCII-A characters and ASCII-N characters as a document index.

For reference, the number of ASCII-A and ASCII-N is expected to be significantly higher than the number of ASCII-C and ASCII-S for normal document files. For example, the number of ASCII-A characters in a document file such as 'novel' and 'report' is overwhelming, and the number of ASCII-N characters in a document file such as 'accounting book' is overwhelming. Accordingly, the information analyzing unit 230 can process an operation according to the relationship between the number of ASCII-C, ASCII-S, ASCII-A, and ASCII-N characters according to the type of the document file.

The information analyzing unit 230 may calculate the information index by using the significance index, the nonsense index, and the document index.

In FIG. 7, only the ASCII code table is shown as the information analysis standard. However, the information analysis unit 230 according to the embodiment of the present invention can use other standard codes such as Unicode as the information analysis standard. That is, when Unicode is used as the information analysis standard, the number of characters corresponding to the code code set (which may be referred to as 'UNICODE-C') can be calculated as a meaningless index. At this time, it is also possible to use a plurality of standard codes such as Unicode and ASCII codes as a standard for analyzing information.

Returning to FIG. 6, the concealment information extracting unit 240 extracts the concealed information bits hidden in each bit block based on the result of the primary decoding and the calculated information index. Then, the concealment information extracting unit 240 performs a second-order decoding for converting the bit value before the first-order decoding for each bit block based on the value of the extracted conceal information bit.

Specifically, when decoding of the corresponding bit block fails as a result of first decoding the information hiding document file in the restoration format, the hidden information bit has a value set to invert the bit value of the corresponding bit block.

For example, when the value of the secret information bit set to perform the secondary encoding for inverting the bit value of the bit block of the compressed document file is '1' in the reversible information concealment apparatus 100, It can be seen that the secret information bit '1' is hidden in the bit block. At this time, the concealment information extracting unit 240 extracts the concealed information bit '1' and inverts the bit value of the corresponding bit block in units of one bit. For reference, the value of the secret information bit for inverting the bit value of the corresponding bit block may be set to either '1' or '0'.

On the other hand, when the primary decoding is successful, there is a possibility that the secret information bit hidden in the corresponding bit block is '1' or '0'. Accordingly, the concealment information extracting unit 240 extracts the concealed information bits based on the result of comparing the information index calculated for the bit block for which the first-order decoding has been successfully performed and the predetermined information index threshold value. For reference, the concealment information extracting unit 240 can obtain the information index threshold value input from the reversible information concealment apparatus 100 through the compressed document input unit 210. [

At this time, the concealment information extracting unit 240 may extract the concealment information bits based on at least one of the significance index, the meaninglessness index, and the document index among the information indexes calculated for the first decoded bit block.

Specifically, if the calculated significance index is lower than a predetermined range of significance indexes, the concealment information extracting unit 240 determines that the significance word is less than a certain standard in the corresponding bit block as compared with the original document file .

For example, it is assumed that the bit block of FIG. 4B is the first decoded bit block, and that the bit block of FIG. 4A is a bit block of the original document file. At this time, it can be predicted that the significance index calculated based on the characters included in the first decoded bit block is significantly lower than the significance index threshold calculated based on the characters included in the bit block of the original document file.

As such, if the calculated significance index is lower than the significance index threshold value, the result of the first decoding can be judged unsuccessfully. That is, it is determined that the corresponding bit block is inverted without maintaining the bit value in the bit block of the original document file. Accordingly, the concealment information extracting unit 240 extracts the concealed information bits having the previously set values so as to invert the bit values, as the concealed information bits concealed in the corresponding bit block. Then, the concealment information extracting unit 240 inverts the bit value before the primary decoding of the bit block in units of one bit.

On the other hand, if the calculated significance index is equal to or smaller than the threshold value of the significance index, the concealment information extracting unit 240 determines that the corresponding bit block includes the same or similar number of significant words as the original document file. Accordingly, the concealment information extracting unit 240 extracts concealment information bits having a preset value so as to hold the bit values of the bit block, as the concealed information bits concealed in the corresponding bit block. Then, the concealment information extracting unit 240 maintains the bit value before the primary decoding of the corresponding bit block.

Meanwhile, the concealment information extracting unit 240 extracts the concealment index of the first-decoded bit block from the original document file by a predetermined criterion or more It is judged that many meaningless characters are included.

For example, the bit block of FIG. 4B includes two ASCII-N (i.e., '5' and '4') characters, four ASCII-S $ 'And'? ') Characters. On the other hand, the bit block in FIG. 4A does not include the ASCII-N character and the ASCII-S character. Assuming that the bit block of FIG. 4B is the first decoded bit block and that the bit block of FIG. 4A is a bit block of the original document file, the first decoded bit block Is comprised of a number of ASCII-C characters compared to the bit block of the original document file, it is determined that the primary decoding is unsuccessful. Accordingly, the concealment information extracting unit 240 can extract, from the first decoded bit block, the concealment information bit having a preset value to invert the bit value of the bit block. Then, the concealment information extracting unit 240 inverts the bit value before the first-order decoding of the bit block in units of one bit according to the extracted concealment information bit.

On the other hand, the concealment information extracting unit 240 judges that, if the calculated insignificant index is less than or equal to the meaningless index threshold value, the bit block includes the same or a similar number of meaningless characters as the original document file. That is, it is determined that the primary decoding is successful. Accordingly, the concealment information extracting unit 240 extracts the concealed information bits having the preset values from the first decoded bit block to hold the bit values of the bit blocks. Then, the concealment information extractor 240 maintains the bit value of the bit block before the first-order decoding according to the value of the extracted concealment information bit.

On the other hand, when the document index calculated for the first decoded bit block is higher than a preset threshold value of the document index, the concealment information extracting unit 240 inserts only the specific document into the corresponding bit block It is judged that a certain number of characters are included more than a predetermined standard. That is, it is determined that the corresponding bit block is inverted without maintaining the bit value in the bit block of the original document file. Accordingly, the concealment information extracting unit 240 extracts the concealed information bits having the previously set values so as to invert the bit values, as the concealed information bits concealed in the corresponding bit block. Then, the concealment information extracting unit 240 inverts the bit value before the primary decoding of the bit block in units of one bit.

On the other hand, if the calculated document index is less than or equal to the document index threshold value, the concealment information extracting unit 240 determines that the specific block has the same or similar number as the original document file in the corresponding bit block. That is, it is determined that the primary decoding is successful. Accordingly, the concealment information extracting unit 240 extracts the concealed information bits having the preset values from the first decoded bit block to hold the bit values of the bit blocks. Then, the concealment information extractor 240 maintains the bit value of the bit block before the first-order decoding according to the value of the extracted concealment information bit.

Referring back to FIG. 6, the document restoring unit 250 decodes the bit block converted (i.e., 'inverted' or 'maintained') by the bit value into the restoration format through the hidden information extracting unit 240, Restore to a file.

Hereinafter, a method for extracting reversible information according to an embodiment of the present invention will be described in detail with reference to FIG.

8 is a flowchart for explaining a reversible information extraction method according to an embodiment of the present invention.

First, the reversible information concealment apparatus 100 receives the information concealment document file in which the confidential information data is encoded in the compressed document file (S810).

At this time, at step S810, at least one of the information index threshold value calculated based on the characters included in the bit block of the original document file and the length information of the bit block may be further input.

Then, the information hiding document file is decoded in units of a predetermined length by applying a preset restoration format (S820).

Next, an information index is calculated based on the plurality of characters included in the decoded bit block (S830).

Specifically, a character included in the decoded bit block is analyzed based on a predetermined information analysis criterion, and at least one information index among a significance index, a meaninglessness index, and a document index is calculated according to a result of the analysis.

At this time, by using a predetermined 'dictionary' as an information analysis standard, a significant word included in a 'dictionary' among words by a plurality of characters included in a bit block is extracted and a significance index is calculated based on the number of significant words can do.

Then, a computer standard code including a predetermined character code, a numeric code, a code code, and a control code is used as an information analysis standard to extract a corresponding computer standard code for each of a plurality of characters included in the bit block, The meaninglessness index can be calculated based on the number of characters corresponding to the code code in the standard code.

Further, a computer standard code including a predetermined character code, a numeric code, a code code, and a control code is used as an information analysis standard to extract a corresponding computer standard code for each of a plurality of characters included in a bit block, The document index can be calculated based on the number of characters corresponding to at least one of the letter code and the numeric code in the standard code, and the number of characters corresponding to at least one of the code code and the control code.

Next, the hidden information bits hidden in the bit block are extracted based on a result of comparing the calculated information index and a preset information index threshold (S840).

At this time, a secret information bit of one bit unit per bit block is extracted. The first secret information bit having the first bit value is extracted according to the result of comparing the calculated information index and the information index threshold value, The second hidden information bit having the second bit value whose value is inverted can be extracted.

Then, the bit value before decoding is converted for each bit block based on the value of the secret information bit (S850).

Specifically, the bit value of each bit block is maintained or inverted in units of one bit according to the value of the extracted hidden information bit.

Then, the bit block in which the bit value is converted is decoded into the restoration format and restored to the original document file (S860).

6 to 8, the reversible information extracting apparatus 200 extracts the secret information bits in units of one bit per bit block of the information hiding document file and then performs secondary decoding on the extracted information bits.

However, the reversible information extracting apparatus 200 according to another embodiment of the present invention can extract the secret information bits of two or more bits per bit block of the information hiding document file to process the secondary decoding. At this time, the reversible information extraction apparatus 200 receives a random number bit stream matched by the value of the secret information bit from the reversible information concealment apparatus 100. [ The reversible information extracting apparatus 200 extracts the hidden information bits for each bit block based on the comparison result between the information index calculated for each bit block of the information hiding document file and the predetermined information index threshold value, do. In addition, the reversible information extracting apparatus 200 performs the secondary decoding on the information hiding document file based on the extracted bit information for each bit block.

Embodiments of the present invention may also be embodied in the form of a recording medium including instructions executable by a computer, such as program modules, being executed by a computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer-readable medium may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes any information delivery media, including computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transport mechanism.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

10: reversible information concealment system
100: reversible information concealment device
200: reversible information extraction device

Claims (20)

A reversible information concealment apparatus comprising:
A document compression unit for primarily encoding an original document file into a predetermined compression format and outputting a compressed document file;
Dividing the bit stream of the compressed document file into a plurality of bit blocks each having a predetermined first length and dividing the predetermined hidden information data into a plurality of hidden information bits each having a predetermined second length, And an information concealment processing unit for processing a second encoding process for converting a bit value of the bit block based on the value of the allocated secret information bit; And
And an information hiding document providing unit for providing an information hiding document file including the bit blocks obtained by converting the bit values. The method according to claim 1,
The information concealment processing unit,
And the bit value of the bit block is maintained or reversed in units of one bit according to the value of the allocated secret information bit. The method according to claim 1,
The information concealment processing unit,
Generating a plurality of random bit streams having a length corresponding to the length of the bit block,
A random number bit stream matched with the allocated secret information bits, and an XOR operation or an XOR operation of the bit blocks in units of one bit. The method according to claim 1,
A bit stream of the original document file is divided into a plurality of bit blocks, and a plurality of characters included in each of the bit blocks are analyzed according to a predetermined information analysis standard to calculate at least one of a significance index, a meaninglessness index, and a document index And an information index threshold value setting unit for setting at least one of the calculated significance index, the meaninglessness index, and the document index as an information index threshold value,
Wherein the information hiding document providing unit comprises:
And provides the information index threshold value to the reversible information extracting apparatus. 5. The method of claim 4,
The above-
Wherein the predetermined information is set to at least one of a predetermined dictionary and a computer standard code. A reversible information extracting apparatus comprising:
A compressed document input unit for receiving an information hiding document file in which secret information data is encoded in a compressed document file;
A restoration preprocessor for first decoding the information hiding document file in units of a predetermined number of bit blocks by applying a predetermined restoration format;
Analyzing a plurality of characters included in the first decoded bit block based on a predetermined information analysis criterion and calculating an information index including at least one of a significance index, a meaningless index, and a document index according to the analyzed result Information Analysis Department;
Extracting a hidden information bit hidden in the bit block based on a result of comparing the calculated information index and a predetermined information exponent threshold value and outputting a bit value before the primary decoding for each bit block, A concealment information extracting unit for processing the second decoding to convert the second information based on the value; And
And a document decompression unit decoding the bit block into which the bit value is converted through the secret information extracting unit into the restoration format and restoring the bit block into an original document file. The method according to claim 6,
Wherein the hidden information extracting unit extracts,
Extracting the secret information bits in units of one bit per bit block,
Extracting a first hidden information bit having a first bit value or a second hidden information bit having a second bit value in which the first bit value is inverted according to a result of comparing the calculated information index and the information index threshold value, However,
And the bit value for each bit block is maintained or inverted in units of one bit according to the value of the extracted secret information bit. The method according to claim 6,
Wherein the compressed document input unit comprises:
The information index threshold value calculated for each bit block of the original document file is further input from the reversible information concealment apparatus,
The information index threshold value is a value
And a threshold value of at least one of the significance index, the no-sense index, and the document index. The method according to claim 6,
The information analyzing unit,
Extracting a meaning word included in the dictionary from a plurality of characters included in the bit block using a predetermined dictionary as the information analysis criterion,
And calculating the significance index based on the number of the significant words. The method according to claim 6,
The information analyzing unit,
Extracting a corresponding computer standard code for each of a plurality of characters included in the bit block by using a computer standard code including a predetermined character code, a numeric code, a code code and a control code as the information analysis reference, And the number of characters corresponding to the code code among the computer standard codes is calculated. The method according to claim 6,
The information analyzing unit,
Extracting a corresponding computer standard code for each of a plurality of characters included in the bit block by using a computer standard code including a predetermined character code, a numeric code, a code code and a control code as the information analysis reference, Calculating a document index based on a first number of characters corresponding to at least one of the letter code and the numeric code among the computer standard codes and a second number of characters corresponding to at least one of the code code and the control code Information extraction device. A method for concealing information in a precompressed document file by a reversible information concealment device,
(a) outputting a compressed document file by first encoding an original document file in a predetermined compression format;
(b) dividing the bit stream of the compressed document file into a plurality of bit blocks each having a predetermined first length;
(c) allocating a plurality of concealment information bits obtained by dividing predetermined concealment information data by a predetermined second length unit to the plurality of bit blocks;
(d) processing a secondary encoding that transforms the bit value of the bit block based on the value of the allocated secret information bit; And
(e) providing an information hiding document file including the bit blocks into which the bit values are transformed. 13. The method of claim 12,
The step (d)
And the bit value of the bit block is maintained or inverted in units of one bit according to the value of the allocated secret information bit. 13. The method of claim 12,
The step (d)
Generating a plurality of random bit streams having a length corresponding to the length of the bit block;
Matching the random bitstreams different for each value of the allocated secret information bits; And
A random number bit stream matched with the allocated secret information bits, and XORing or XORing the bit blocks in units of one bit. 13. The method of claim 12,
Prior to step (e)
Dividing a bit stream of the original document file into a plurality of bit blocks;
Calculating at least one of a significance index, a meaninglessness index, and a document index by analyzing a plurality of characters included in each of the bit blocks of the original document file according to a predetermined information analysis criterion; And
Setting at least one of the calculated significance index, the meaninglessness index, and the document index to an information index threshold value,
The step (e)
Wherein the information index threshold value is further provided to a reversible information extracting apparatus. A method for extracting secret information data hidden in an information hiding document file by a reversible information extraction device,
(a) receiving the information hiding document file in which secret information data is encoded in a compressed document file;
(b) first decoding the information hiding document file in units of a predetermined length by applying a preset restoration format;
(c) analyzing a plurality of characters included in the first decoded bit block on the basis of a predetermined information analysis criterion, and calculating an information index including at least one of a significance index, a no- ;
(d) extracting the hidden information bits hidden in the bit block based on a result of comparing the calculated information index with a preset information index threshold value;
(e) processing a secondary decoding for converting the bit value before the primary decoding on the bit block basis based on the value of the secret information bit; And
(f) decoding the bit block into which the bit value has been converted into the restoration format and restoring the same into an original document file. 17. The method of claim 16,
The step (d)
Extracting the secret information bits in units of one bit per bit block,
Extracting a first hidden information bit having a first bit value or a second hidden information bit having a second bit value in which the first bit value is inverted according to a result of comparing the calculated information index and the information index threshold value, and,
The step (e)
Wherein the bit value of each bit block is maintained or inverted in units of one bit according to the value of the extracted hidden information bit. 17. The method of claim 16,
The step (c)
Extracting a meaning word included in the dictionary from among a plurality of characters included in the bit block using a predetermined dictionary as the information analysis reference; And
And calculating the significance index based on the number of the significant words. 17. The method of claim 16,
The step (c)
Extracting a corresponding computer standard code for each of a plurality of characters included in the bit block using a computer standard code including a predetermined character code, a numeric code, a code code, and a control code as the information analysis reference; And
And calculating the nonsense index based on the number of characters corresponding to the code code among the extracted computer standard codes. 17. The method of claim 16,
The step (c)
Extracting a corresponding computer standard code for each of a plurality of characters included in the bit block using a computer standard code including a predetermined character code, a numeric code, a code code, and a control code as the information analysis reference; And
Calculating the document index based on a first number of characters corresponding to at least one of the letter code and the numeric code among the extracted computer standard codes and a second number of characters corresponding to at least one of the code code and the control code And extracting the reversible information.

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