Patent Grant
9462152
The embodiments described herein pertain generally to a system and a method for hiding reversible information in a compressed image and extracting the information hidden in the compressed image.
Various information protection techniques are being developed to protect digital media that can be easily copied or modified.
Among the techniques, information hiding as well as encoding is being widely used to assure confidentiality. According to this information hiding technique, a digital medium can be modified, and data can be embedded into the digital medium.
In this regard, Korean Patent Application Publication No. 10-2007-0076130 (Title of Invention: “Information Embedding and Extracting Method for Image Authentication”) describes a lossless data embedding method, which does not cause a loss of original data during processes of embedding and extracting information; according to the method, an image is divided into a multiple number of blocks, each of the divided blocks is divided into sub-blocks, and authentication information is embedded into one pixel of each of the sub-blocks, wherein the authentication information (binary information) is inserted into a pixel having a minimum pixel value.
However, there has been a limit since it is not easy to reversibly hide information in a compressed image, and not an original image, as a random number output is generated when an image is compressed.
In order to solve the foregoing problems, example embodiments provide an apparatus and a method for hiding information, which additionally encode and hide information in an already compressed image, and an apparatus and a method for extracting information from an image file, in which information has been hidden.
However, the problems sought to be solved by the present disclosure are not limited to the above description, and other problems can be clearly understood by those skilled in the art from the following description.
According to one example embodiment, there is provided a reversible information hiding apparatus, comprising: an image compressing unit that encodes an original image file to output a compressed image file by applying a preset compression format; an information hiding processing unit that divides a bit stream of the compressed image file into a plurality of bit blocks each having a preset length, allocates, to the plurality of the bit blocks, a plurality of hiding information bits obtained from dividing preset hiding information data into preset length units, and converts bit values of the bit blocks based on values of the allocated hiding information bits; and an information-hidden image providing unit that provides a reversible information extracting apparatus with the information-hidden image file comprising the bit blocks, of which the bit values have been converted.
Especially, the reversible information extracting apparatus may comprise a compressed image inputting unit that receives input of an information-hidden image file, in which hiding information data have been encoded in a compressed image file, from a reversible information hiding apparatus; a restoration pre-processing unit that decodes the information-hidden image file in a bit block unit with a preset length by applying a preset restoration format; a blocky effect calculating unit that calculates a blocky effect value based on subtraction of boundary pixel values between each of the pixel blocks of the decoded bit blocks and at least one adjacent pixel block thereof; a hidden information extracting unit that extracts hiding information bits hidden in the bit blocks based on a result of comparing the calculated blocky effect values and the preset blocky effect threshold value, and converts the bit values of the bit blocks prior to the decoding based on values of the hiding information bits; and an image restoring unit that decodes the bit blocks, of which the bit values have been converted, in the restoration format through the hidden information extracting unit to restore the original image file.
According to another example embodiment, there is provided method enabling a reversible information hiding apparatus to hide information in a pre-compressed image file, the method comprising: (a) encoding an original image file in a preset compression format to output a compressed image file; (b) dividing a bit stream of the compressed image file into a plurality of bit blocks each having a preset length; (c) allocating, to the plurality of the bit blocks, a plurality of hiding information bits obtained from dividing preset hiding information data into preset length units; (d) converting bit values of the bit blocks based on values of the allocated hiding information bits; and (e) providing the reversible information extracting apparatus with an information-hidden image file comprising the bit blocks, of which the bit values have been converted.
According to still another example embodiment, there is provided a method enabling a reversible information extracting apparatus to extract hiding information data hidden in an information-hidden image file, comprising: (a) receiving input of the information-hidden image file, in which hiding information data have been encoded in a compressed image file, from a reversible information hiding apparatus; (b) decoding the information-hidden image file in a bit block unit with a preset length by applying a preset restoration format; (c) calculating a blocky effect value based on subtraction of boundary pixel values between each of the pixel blocks of the decoded bit blocks and at least one adjacent pixel block thereof; (d) extracting hiding information bits hidden in the bit blocks based on a result of comparing the calculated blocky effect values and the present blocky effect threshold value; (e) converting the bit values of the bit blocks prior to the decoding based on values of the hiding information bits; and (f) decoding the bit blocks, of which the bit values have been converted, in the restoration format to restore the original image file.
According to the example embodiments, through the reversible encoding technique, which is capable of thoroughly restoring data without needing to modify original data, hiding information data can be additionally encoded without causing a data loss of an already compressed image file.
Further, according to the example embodiments, an accurate decoding outcome can be acquired by decoding an image file obtained from additionally encoding hiding information data on a compressed image file, by using blocky effect values among adjacent pixel blocks.
Hereinafter, example embodiments will be described in detail so that inventive concept may be readily implemented by those skilled in the art. However, it is to be noted that the present disclosure is not limited to the example embodiments and examples but can be realized in various other ways. In drawings, parts not directly relevant to the description are omitted to enhance the clarity of the drawings, and like reference numerals denote like parts through the whole document.
Throughout the whole document, the terms “connected to” or “coupled to” are used to designate a connection or coupling of one element to another element and include both a case where an element is “directly connected or coupled to” another element and a case where an element is “electronically connected or coupled to” another element via still another element. Further, through the whole document, the term “comprises or includes” and/or “comprising or including” used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements unless context dictates otherwise.
As shown in
Specifically, the reversible information hiding apparatus 100 processes second encoding to hide information data (bk) in a compressed image (Xk), which has been subject to first encoding in a set compression format, and output an information-hidden image (Yk) as a result of the second encoding.
The reversible information extracting apparatus 200 receives input of the information-hidden image (Yk) provided from the reversible information hiding apparatus 100, and extracts the hidden information data (bk) from the information-hidden image (Yk) to acquire the compressed image (Xk). The reversible information extracting apparatus 200 decodes the compressed image (Xk) based on the extracted hidden information data (bk) to restore an original image.
Hereinafter, a configuration and an operation of the reversible information hiding apparatus according to an example embodiment is described in detail.
As shown in
The image compressing unit 110 encodes (i.e., ‘first encoding’) an original image file in a preset compression format and outputs the compressed image file.
The information hiding processing unit 120 divides a bit stream of the compressed image file output from the image compressing unit 110 into a multiple number of bit blocks, and allocates and hides (i.e., ‘second encoding’) hiding information data in the respective bit blocks.
Specifically, the information hiding processing unit 120 divides the bit stream of the compressed image file into a multiple number of bit blocks each having a preset length (hereinafter, referred-to as ‘L’). Additionally, for the hidden information extraction processing in the reversible information extracting apparatus 200 as described later, the information hiding processing unit 120 may further provide length information (i.e., ‘L’) for the bit blocks through the information-hidden image providing unit 130.
In addition, the information hiding processing unit 120 divides a bit stream of preset hiding information data into bit units each having a preset length (i.e., bit digits) to generate a multiple number of hiding information bits. In this case, the information hiding processing unit 120 may divide the hiding information data into single-digit or at least two (2)-digit bit units.
For example,
As shown in
The information hiding processing unit 120 allocates the hiding information bits to the multiple bit blocks, respectively, and performs encoding (i.e., ‘second encoding’), in which according to values of the allocated hiding information bits, bit values of the corresponding bit blocks are converted.
Specifically, if hiding information bits in a single-digit bit unit are allocated to the respective bit blocks, the information hiding processing unit 120 holds or reverses the bit values of the bit blocks in a 1 bit unit according to the values of the corresponding hiding information bits.
For example, the information hiding processing unit 120 hides information by holding a value of a first bit block (hereinafter, referred-to as a ‘top-level bit block’) of the payload of the compressed image file, and applying the operation of Formula 1 below to the other bit blocks.
If bk=0,Yk=Xk
If bk=1,Yk=
That is, if a value of a hiding information bit is a single-digit bit ‘0’, bits of the bit blocks (Xk) are output while being held as they are. On the other hand, if a value of a hiding information bit is a single-digit bit ‘1’, bits of the bit blocks (Xk) are reversed in a 1 bit unit and output. Additionally, the values of the hiding information bits that hold or reverse the bit values of the bit blocks may be mutually changed.
In addition, the information hiding processing unit 120 may hide hiding information bits in a two (2) or more-digit bit unit.
Specifically, the information hiding processing unit 120 generates a multiple number of random number bit streams each having a length corresponding to the length of the bit block, and matches different random number bit streams according to values of the allocated hiding information bits. In addition, the information hiding processing unit 120 processes second encoding through exclusive OR (or exclusive NOR) operation in a 1 bit unit between the respective random number bit streams and the bit blocks.
For example, if a hiding information bit is a two (2)-digit bit, the information hiding processing unit 120 changes a bit value each digit bit of the bit block according to the random number bit stream matched the bit value of the hiding information bit, by applying Formula 2 below.
If bk=0 (i.e., 002),Yk=Xk+R0
If bk=1, (i.e., 012),Yk=Xk+R1.
If bk=2 (i.e., 102),Yk=Xk+R2
If bk=3 (i.e., 112),Yk=Xk+R3 <Formula 2>
That is, if a value of a hiding information bit (bk) is a two (2)-digit bit ‘002,’ a random number bit stream ‘R0’ matches, and the bit block (Xk) and each digit bit of the random number bit stream R0 are subject to an XOR operation so that a bit block, in which information is hidden, is output. In this manner, if K different random numbers are used for the random number bit streams, a ‘log2 K’ hiding information bit per bit block may be hidden.
As described, when two (2) or more-digit hiding information bits are hidden in the bit blocks, the information hiding processing unit 120 may provide the reversible information extracting apparatus 200 with random number bit streams matching with the values of the hiding information bits, respectively, through the information hiding image providing unit 130.
Meanwhile, as shown in
In addition, the information hiding processing unit 120 may set the sequence of encoding the bit blocks of the compressed image file to be non-sequential, in order to increase the accuracy in the hiding information extraction and the original image restoration processing in the reversible information extracting apparatus 200.
Specifically, the information hiding processing unit 120 divides an image frame of an original image file into a multiple number of pixel blocks, and sets the sequence of processing second encoding of bit blocks corresponding to the pixel blocks, respectively, to be non-sequential based on a positional sequence of the pixel blocks. Hereinafter, the result of non-sequentially processing the second encoding of the bit blocks of the compressed image file based on the positional sequence of the pixel blocks is described in detail with reference to
The information-hidden image providing unit 130 provides the reversible information extracting apparatus 200 with an information-hidden image file, which includes the bit blocks that have been subject to the second encoding (i.e., conversion of bit values).
Meanwhile, in order to enable the reversible information extracting apparatus 200 to successfully extract hiding information data hidden in the information-hidden image file and restore the original image file, a blocky effect value among the pixel blocks corresponding to the respective bit blocks in the image frame of the original image file is necessary.
To this end, the reversible information hiding apparatus 100 includes a blocky effect threshold value setting unit 140.
The blocky effect threshold value setting unit 140 divides the image frame of the original image file into a multiple number of pixel blocks each having a preset size, and calculates a blocky effect value based on subtraction of boundary pixel values between each of the pixel blocks and at least one adjacent pixel block thereof. In addition, the blocky effect threshold value setting unit 140 sets a blocky effect threshold value based on the blocky effect values for the pixel blocks.
In this case, the blocky effect threshold value setting unit 130 may provide the reversible information extracting apparatus 200 with the blocky effect threshold values through the information-hidden image providing unit 130.
Specifically,
For example, the blocky effect threshold value setting unit 140 calculates a blocky effect threshold value B based on subtraction of pixel values between the boundary pixels, by using Formula 3 below.
Formula 3 shows setting the blocky effect threshold value B by calculating a mean absolute difference (MAD) value, which is obtained by averaging absolute values of the pixel values for the boundary pixels of the adjacent pixel blocks.
Hereinafter, a reversible information hiding method according to an example embodiment is described in detail with reference to
First, an original image file is encoded using a preset compression format, and the compressed image file is output (S710).
A bit stream of the compressed image file is divided into a multiple number of bit blocks each having a preset length (S720).
Thereafter, a multiple number of hiding information bits obtaining from dividing preset hiding information data into preset length units are allocated to the multiple bit blocks (S730).
In this case, in S730, the image frame of the original image file is divided into a multiple number of pixel blocks each having a preset size. In addition, a sequence of allocating the hiding information bits to the bit blocks corresponding to the pixel blocks, respectively, may be set to be non-sequential based on a positional sequence of the pixel blocks.
Thereafter, based on a value of an allocated hiding information bit, a bit value of the corresponding bit block is converted (S740).
In S740, if a single-digit hiding information bit has been allocated, a bit value of the corresponding bit block may be held or reversed in a 1 bit unit according to the value of the hiding information bit.
In addition, in S740, if an at least two (2)-digit hiding information bit has been allocated, the bit value of the bit block may be converted by applying a random number bit stream matching to each of the hiding information bit values. First, a multiple number of random number bit streams having a length corresponding to the length of the bit block are generated. In addition, different random number bit streams match with the values of the allocated hiding information bits, respectively. Thereafter, a random number bit stream matching with an allocated hiding information bit and the corresponding bit block are subject to an exclusive OR or NOR operation in a 1 bit unit.
Next, the information-hidden image file including the bit blocks, of which the bit values have been converted, is provided to the reversible information extracting apparatus (S750).
In this case, in S750, length information preset for the bit bocks and the random number bit streams matching with the values of the hiding information bits are provided to the reversible information extracting apparatus 200 together with the information-hidden image file.
Meanwhile, in S720, the bit stream of the payload of the compressed image file, except for the header thereof, is divided into the multiple bit blocks, and as a result, S730 and S740 may process the bit blocks other than the top-level bit block of the payload.
In addition, the example embodiments may include steps of dividing the image frame of the original image file into a multiple number of pixel blocks each having a preset size, calculating a blocky effect value based on subtraction of boundary pixel values between each of the pixel blocks and at least one adjacent pixel block thereof, and setting a blocky effect threshold value based on the blocky effect values for the pixel blocks, prior to S750. In this case, in S750, the blocky effect threshold value may be further provided to the reversible information extracting apparatus 200.
Hereinafter, a configuration and an operation of the reversible information extracting apparatus 200 according to an example embodiment are described in detail.
As shown in
The compressed image inputting unit 210 receives input of an information-hidden image file, in which hiding information data have been encoded into a compressed image file, from the reversible information hiding apparatus 100.
In this case, the compressed image inputting unit 210 further receives input of a blocky effect threshold value set based on the blocky effect values of the pixel blocks of the image frame of the original image file, and length information for the bit block unit, from the reversible information hiding apparatus 100.
The restoration pre-processing unit 220 decodes the information-hidden image file in a preset restoration format, and decodes the information-hidden image file in a bit block unit having a preset length (hereinafter, referred-to as ‘first decoding’). In this case, the preset restoration format corresponds to the compression format used when the reversible information hiding device 100 compresses the original image file.
The blocky effect calculating unit 230 calculates a blocky effect value based on subtraction of boundary pixel values between each of the pixel blocks of the bit blocks, which have been subject to the first decoding, and at least one adjacent pixel block thereof.
In this case, the blocky effect calculating unit 230 calculates subtraction of boundary pixel values between the pixel blocks of the bit blocks, which have been subject to the first decoding, and their adjacent pixel blocks, and calculates an average value of absolute values obtained from the subtraction of the boundary pixel values. The method of calculating a blocky effect value in the blocky effect calculating unit 230 may correspond to the method of calculating a blocky effect threshold value in the reversible information hiding apparatus 100.
The hidden information extracting unit 240 extracts information bits hidden in the bit blocks based on a result of comparing the calculated blocky effect values and the preset blocky effect threshold value, and processes second decoding to convert the bit values of the bit blocks prior to the first decoding based on the values of the hiding information bits. Additionally, the hidden information extracting unit 240 holds the bit value of the top-level bit block of the payload of the information-hidden image file, and converts the bit values of the bit blocks other than the top-level bit block.
Specifically, when the information-hidden image file is subject to first decoding in a bit block unit, if the decoding of the corresponding bit block is failed, a value of a hiding information bit will be a value that reverses the bit value of the corresponding bit block. For example, when the value of the hiding information bit is ‘1’, if the reversible information hiding apparatus 100 has performed second encoding to reverse the bit value of the bit block of the compressed image file, it can be understood that the value of the hiding information bit will be ‘1’ upon failure of decoding. On the other hand, if the decoding is successfully performed, the hiding information bit hidden in the corresponding bit block is likely to be ‘1’ or ‘0.’
Accordingly, the hidden information extracting unit 240 calculates a blocky effect value between the pixel block of the bit block, for which first decoding has been successfully performed, and its adjacent pixel block, to determine whether the bit value of the corresponding bit block has been held or reversed.
In this case, the hidden information extracting unit 240 extracts a hiding information bit in a single-digit bit unit per bit block, and extracts a first hiding information bit having a first bit value when a calculated blocky effect value exceeds the preset blocky effect threshold value. In addition, the hidden information extracting unit 240 performs second decoding to hold or reverse the bit value of the corresponding bit block in a 1 bit unit according to the value of the extracted hiding information bit.
Meanwhile, when the blocky effect values for the bit blocks are calculated, other bit blocks, for which second decoding has been completed, may be used so as to calculate a more accurate blocky effect value for the corresponding bit block.
Specifically,
In this case, as shown in
Meanwhile, the sequence of encoding the bit blocks of the information-hidden image file in the reversible information hiding device 100 may be non-sequential based on the positional sequence of the pixel blocks on the image frame of the original image file. Accordingly, first and second decoding of the bit blocks of the information-hidden image file may be processed starting from a bit block corresponding to an adjacent pixel block in at least one of upper, lower, front and rear positions around a random pixel block according to the positional sequence on the image frame. For example, in
As another example,
Specifically, it is described hereinafter that one bit block corresponds to one pixel block on an image frame of the information-hidden image file. In addition, each bit block is indicated to correspond to the decoding sequence. In this case, a bit block 1 (i.e., the top-level bit block) corresponding to a first pixel block is a bit block, of which the original data have been held without second encoding at the time of encoding in the reversible information hiding apparatus 100. Accordingly, a first decoding result may be used as it is. After first decoding of the bit block 1, a blocky effect value is calculated by using the bit block 1 adjacent to the left side of the bit block 2 upon decoding of the bit block 2. Upon decoding of the bit block 3 thereafter, a block effect value is calculated by using the bit block 1 adjacent to the upper side of the bit block 3, and a blocky effect value for the bit block 4 is also calculated by using the bit black 3 adjacent to the upper side of the bit block 4. In addition, a blocky effect value of the bit block 5 is calculated by using the bit block 2 adjacent to the upper side of the bit block 5 and the bit block 3 adjacent to the left side of the bit block 5. In this manner, the bit blocks are decoded in a non-sequential order based on the positional sequence of the pixel blocks on the image frame.
Meanwhile, in
Returning to
Hereinafter, a reversible information extracting method according to an example embodiment is described in detail with reference to
First, an information-hidden image file, in which hiding information data have been encoded in a compressed image file, is input from the reversible information hiding apparatus 100 (S910).
In this case, in S910, at least one of the blocky effect threshold value set based on the blocky effect values among the pixel blocks of the image frame of the original image file and length information of the bit block units may be further input.
Thereafter, the information-hidden image file is decoded in a bit block unit with a preset length by applying the preset restoration format (S920).
In this case, in S920, the decoding may be performed starting from a bit block corresponding to an adjacent pixel block in at least one of upper, lower, front and rear positions around a random pixel block in view of the positional sequence of the pixel blocks in the image frame of the original image file.
Next, a blocky effect value is calculated based on subtraction of boundary pixel values between each of the pixel blocks of the decoded bit blocks and at least one adjacent pixel block thereof (S930).
Specifically, subtraction of boundary pixel values between the pixel blocks of the decoded bit blocks and their adjacent pixel blocks is calculated, and a mean value of absolute values for the subtraction of the boundary pixel values is calculated.
In addition, hiding information bits hidden in the bit blocks are extracted based on a result of comparing the calculated blocky effect values and the preset blocky effect threshold value (S940).
In this case, a hiding information bit in a single-digit bit unit per bit block is extracted. If a calculated blocky effect value exceeds the blocky effect threshold value, a first hiding information bit having a first bit value is extracted. If a calculated blocky effect value is the blocky effect threshold value or less, a second hiding information bit having a second bit value reversed from the first bit value is extracted.
Thereafter, the bit values of the respective bit blocks prior to the decoding are converted based on the values of the hiding information bits (S950).
Specifically, the bit values of the bit blocks are held or reversed in a 1 bit unit according to the values of the extracted hiding information bits. In this case, the bit value of the top-level bit block in the payload of the information-hidden image file is held, and the bit values of the bit blocks other than the top-level bit block are converted.
Thereafter, the bit blocks, of which the bit values have been converted, are decoded in the restoration format to restore the original image file (S960).
However, a reversible information extracting apparatus 200 according to another example embodiment may extract hiding information bits in an at least two (2)-digit bit unit per bit block of the information-hidden image file, and processes second decoding. In this case, the reversible information extracting apparatus 200 may receive random number bit streams matching with the values of the hiding information bits, respectively, from the reversible information hiding apparatus 100. In addition, the reversible information extracting apparatus 200 may extract hiding information bits for the bit blocks and performs second decoding based on the result of calculating blocky effect values between the pixel blocks of the information-hidden image file and at least one adjacent pixel block thereof and the random number bit streams.
Example embodiments can be embodied in a storage medium including instruction codes executable by a computer or processor such as a program module executed by the computer or processor. A computer readable medium can be any usable medium which can be accessed by the computer and includes all volatile/nonvolatile and removable/non-removable media. Further, the computer readable medium may include all computer storage and communication media. The computer storage medium includes all volatile/nonvolatile and removable/non-removable media embodied by a certain method or technology for storing information such as computer readable instruction code, a data structure, a program module or other data. The communication medium typically includes the computer readable instruction code, the data structure, the program module, or other data of a modulated data signal such as a carrier wave, or other transmission mechanism, and includes information transmission mediums.
The above description of the example embodiments is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the example embodiments. Thus, it is clear that the above-described example embodiments are illustrative in all aspects and do not limit the present disclosure. For example, each component described to be of a single type can be implemented in a distributed manner. Likewise, components described to be distributed can be implemented in a combined manner.
The scope of the inventive concept is defined by the following claims and their equivalents rather than by the detailed description of the example embodiments. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the inventive concept.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2013-0001285 | Jan 2013 | KR | national |
| 10-2014-0001368 | Jan 2014 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2014/000101 | 1/6/2014 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/107070 | 7/10/2014 | WO | A |
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| Number | Date | Country | |
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| 20150350486 A1 | Dec 2015 | US |
