KR100965604B1 - Method and Apparatus for Providing Secrete Message Using Image - Google Patents

Abstract

The present invention relates to a message providing method using an image and an apparatus thereof. Message providing apparatus using an image according to an embodiment of the present invention is to distinguish the color channel of the image, each color by using the color difference between each pixel (Pixel) and the surrounding pixels and a predetermined threshold value for each color channel An insertion capacity calculation unit for calculating a message insertion capacity of each pixel for each channel and a message insertion unit for inserting a message in a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel for each color channel; Can be. Accordingly, the present invention has the advantage of providing an image steganography technique capable of improving the insertion capacity of the message and the non-cognition of the stego image by inserting the message adaptively according to the characteristics of the image.

Message, image, pixel, correction, DMT

Description

Method and device for providing message using image {Method and Apparatus for Providing Secrete Message Using Image}

The present invention relates to a method and apparatus for providing a message, and more particularly, to a method and an apparatus for adaptively inserting a message into an image through image processing.

Recently, due to the development of high-speed wired and wireless data communication network, various digital multimedia data are easily and conveniently transmitted through a network.

In particular, as the use of digital multimedia contents spreads rapidly, information protection is recognized as an important problem for users who want to communicate secretly.

Accordingly, the need for digital information protection and concealment, which is open to communication networks, is required in the fields of electronic commerce, intellectual property protection and authentication.

So far, two representative methods of information protection have been introduced, the encryption method and the steganography. In this case, the encryption scrambling the message in a form that cannot be decrypted by another person using a specific encryption algorithm, and only the receiver having the encryption key can decrypt the encrypted message using the encryption key.

The encryption method has been mainly used in the military field, but recently, various encryption algorithms have been provided in wired and wireless communication networks for more secure information transmission.

However, the encryption method is not appropriate when the information exchanged between the sender and the receiver, which is the communication subject, must be transmitted without the knowledge of the confidential information by the third party.

On the other hand, Steganography, which is derived from ancient Greece and means "Covered Writing", is used to exchange images, audio, video, or It is a method of concealing and transmitting to other media called various covers such as text.

In other words, steganography is a method of concealing information so that a third party cannot recognize that the message itself is hidden in the media through human senses.

Recent developments in computers and software that support powerful graphics processing have led to the fastest growth of image-based steganography technology in recent years. Image steganography is a technique based on the fact that in human visual system (HVS), there is a limit to the colors that can be distinguished by humans. Any type of plain text or cipher text can be inserted into the image bit stream.

An object of the present invention for solving the problems of the prior art as described above is an adaptive message providing method using an image capable of adaptively selecting the number of pixels and insertion bits to insert a message by analyzing the characteristics of the image and its It is to provide a device.

It is still another object of the present invention to provide a method and apparatus for adaptive message providing using an image capable of increasing non-cognition by designating a position at which a message is to be inserted using pseudo random numbers.

It is still another object of the present invention to distinguish between flat areas and edge areas based on the RGB color difference with neighboring pixels for each pixel, and to insert more secret data into the edge areas, thereby making it possible to increase image recognition. The present invention provides an adaptive message providing method and apparatus therefor.

Another object of the present invention is to generate one DMT (Difference Mask Table) that records whether a message can be inserted into an RGB color channel per pixel, thereby providing an adaptive message providing method using an image having high processing speed and memory efficiency. To provide a device.

Another object of the present invention is to provide an adaptive message using an image that is capable of improving data insertion capacity and non-awareness by separating RGB colors constituting the image and inserting a large number of messages with respect to a used color. It is to provide a method and an apparatus thereof.

It is another object of the present invention to adaptively correct a stego image according to the RGB color frequency of an image with the lowest LBS of the pixel where the message is not inserted after the message insertion to ensure safety from the statistical attack of stegonalysts. It is to provide a message providing method and an apparatus thereof.

Still another object of the present invention is to provide a method and apparatus for adaptive message providing using an image suitable for a mobile environment.

It is still another object of the present invention to provide an adaptive message providing method and apparatus using an image which can be extended to various fields such as authentication, security, and finance through information concealment as well as image concealment.

Other objects of the present invention will be readily understood through the following description of the embodiments.

According to an aspect of the present invention, a message providing apparatus using an image is disclosed.

Message providing apparatus using an image according to an embodiment of the present invention is to distinguish the color channel of the image, each color by using the color difference between each pixel (Pixel) and the surrounding pixels and a predetermined threshold value for each color channel An insertion capacity calculation unit for calculating a message insertion capacity of each pixel for each channel and a message insertion unit for inserting a message in a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel for each color channel; Can be.

According to another aspect of the present invention, a method of providing a message using an image is disclosed.

In the message providing method according to an embodiment of the present invention, a color channel of an image is distinguished, and each color channel is distinguished by using a color difference between each pixel and surrounding pixels and a predetermined threshold value for each color channel. The method may include calculating a message insertion capacity of a pixel and inserting a message into a color channel of a predetermined pixel included in an image according to the calculated message insertion capacity of each pixel for each color channel.

According to another aspect of the present invention, a method for providing a message through a communication terminal is disclosed.

In a message providing method using a communication terminal according to an embodiment of the present invention, an image is displayed on a message input window, a message is output on the message input window, the message is inserted into the image, and the message is displayed. And inserting the inserted image, wherein inserting the message distinguishes the color channels of the image, and for each of the divided color channels, the color difference between each pixel and the surrounding pixels and a predetermined threshold value. Calculating a message insertion capacity of each pixel for each color channel by using the method; and inserting the message into a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel for each color channel. It may include a step.

The present invention has the advantage of providing an adaptive message providing method and apparatus using the image.

In addition, the present invention has an advantage of providing a method and apparatus for providing a message using an image capable of adaptively selecting the number of pixels and insertion bits into which a message is to be inserted by analyzing characteristics of the image.

In addition, the present invention has the advantage of providing a message providing method and apparatus using an image that can increase the non-cognitive by designating a position to insert the message using a pseudo random number.

The present invention also provides a method for providing a message using an image having high processing speed and memory efficiency by using a DMT (Difference Mask Table) in which color identification information for inserting a message is recorded in a corresponding pixel according to an RGB difference from a neighboring pixel. There is an advantage in providing the device.

In addition, the present invention provides a method and apparatus for providing a message using an image that can improve the data insertion capacity and the non-perception by separating the RGB colors constituting the image and inserting a relatively large number of messages for the most used colors. There is an advantage to provide.

In addition, the present invention is a message using an image capable of correcting the stego image according to the RGB color frequency of the image, the lowest LBS of the pixel that the message is not inserted after the message insertion to ensure safety from the statistical attack of stegoalilyst There is an advantage of providing the method and the apparatus.

In addition, the present invention utilizes a characteristic that is less susceptible to changes in the edge area than the smoothing area due to the characteristics of the human visual perception system. It is advantageous to provide a method and apparatus for providing a message using an image capable of inserting more messages in a pixel having a large difference value by calculating a difference).

Through the above advantages, the present invention has an effect of providing a method and apparatus for providing a message using an image suitable for a mobile environment and commercially available.

In addition, the present invention has the advantage that it can be extended to various fields such as authentication, security and finance through information concealment as well as information concealment.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In this application, the terms "comprising" or "mounted" and "mounted" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, one Or other features or numbers, steps, operations, components, parts or combinations thereof in any way should not be excluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Other aspects, features, and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

Hereinafter, a preferred embodiment of an adaptive message providing method and apparatus using an image according to the present invention will be described in detail with reference to the drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments.

In the following description, a general steganography technique and the conditions of steganography will be briefly described with reference to FIGS. 1 and 2 to aid in understanding the present invention.

1 is a view for explaining a general steganography model.

As shown in FIG. 1, the general steganography technique has the following components.

Message: M

Cover: C

Stego: S

Stego Key: K

Insertion Algorithm: f _E (C, M, K)-> S

Extraction Algorithm: f _E ^-1 (S, K)-> M

Where the insertion algorithm f _E In this case, the message providing device 100 selects the cover C that does not receive any doubt to deliver the message M to the message receiving device 200. Thereafter, the message providing device 100 inserts the message M into the cover C using the stego key K to generate the stego S.

On the other hand, in the case of the extraction algorithm f _E ^{- 1} , the message receiving apparatus 200 extracts the message M with respect to the received stego S using the stego key K.

Here, the stego key K specifies the parameter or function used to insert or extract the message M in the stego S.

Basically, Stego (S) should be created to be indistinguishable from cover (C) so that the attacker cannot recognize the existence of the message. In general, the message providing device 100 may use at least one of various media such as audio, video, image, and text as the cover C.

2 is a view for explaining a general steganography condition.

As shown in FIG. 2, steganography must satisfy embedding capacity, imperceptibility of hidden information, resistance to removal attack, and the like.

Noncognition is the most important requirement of steganography and involves the creation of stego such that a person cannot feel visually or audibly. For example, if it is recognized by the message receiver 200 or an attacker that the cover is damaged, it means that the steganography technique is not recognized.

Unlike a watermark that inserts a small amount of copywriter information, the insertion capacity is related to a capacity for sufficiently inserting a message since steganography is intended for covert communication using a cover. This means that the steganography technique, which can insert a larger amount of messages without damaging the cover, has an excellent insertion capacity.

Robustness is related to the ability to extract the inserted message even if the transformation of Stego occurs during transmission. However, it may be a relatively less important factor compared to other requirements of steganography.

As described above, the steganography technique may be evaluated based on two criteria, message insertion capacity and stego quality. In general, if a message of considerable size can be inserted into the cover and the cover-to-stego similarity can be maintained, it can not be suspected by an illegal user during the transmission of the information.

3 and 4 are diagrams for explaining the message providing apparatus according to an embodiment of the present invention.

Referring to FIG. 3, the message providing apparatus 100 according to the present invention includes a message generator 310, a compressor 320, an encryption unit 330, a stego image generator 340, and a transmitter 350. can do.

The message providing device 100 is a device for generating a stego image by inserting a message into an image. The message providing device 100 may be an electronic device such as a computer, a mobile phone, a PDA, or a communication terminal with a communication function.

The message generator 310 generates a message to be inserted into the image. The message generator 310 may input a message to be inserted into an image by the user through an input device of the electronic device, or retrieve a pre-stored message. Here, the message may include text, images, audio, video, and the like.

The compression unit 320 inserts more messages into the image and compresses the messages in order to prevent deterioration of the image quality of the Stego image generated after the insertion of the message.

The encryption unit 330 encrypts the message before insertion of the message to hide the characteristic pattern of the original message. As the encryption method, various methods such as a public key method and a secret key method may be selected, and in the case of the secret key method, the used secret key may be received by the message providing device 100 and the message before transmitting the stego image. May be shared to device 200.

The stego image generating unit 340 inserts an encrypted message into the cover message to generate a stego image. The stego image generator 340 inserts a message into the image using a stego key. Here, the stego key specifies a parameter used for inserting a message, for example, a threshold for calculating an insertion capacity, or a function, for example, a pseudo random function for calculating an insertion position.

Referring to FIG. 4, the stego image generating unit 340 may include an image scanning unit 410, an insertion capacity calculation unit 420, an insertion position calculation unit 430, and a message insertion unit 440.

The image scanning unit 410 scans an image to be used as a cover, and generates a predetermined matrix D _{i, j} corresponding to the size of the scanned image.

For example, if the resolution of the scanned image is 1024x800, the matrix D _{i, j} may have a size of i (row) of 1024 and j (column) of 800.

The image may be input by the user, a pre-stored image may be loaded, and downloaded through a communication network.

The insertion capacity calculator 420 calculates an insertion capacity of an image for inserting a message into the scanned image.

The insertion capacity calculator 420 includes a color channel separator 422, a PVD calculator 424, a DMT generator 426, and an insertion capacity calculator 428.

The color channel separator 422 classifies the scanned image for each color channel. The color channel can be divided into three colors, RGB (Red, Green, and Blue).

The PVD calculator 424 compares the color difference between each pixel and neighboring pixels with a preset threshold, and then calculates the PVD for each pixel.

Here, the PVD for each pixel may be calculated by assigning weights for each color channel to be easily distinguished through a predetermined color channel mask. For example, when the size of each element of the matrix is 1 byte, the weights for the R / G / B color channels may be assigned values of 1,2 and 4, respectively. That is, the color channels by weight P ^{n -,} where, P is a natural number of 2 or more, n is a natural number including 0, and may have a value of n may be a different value from each other for each color channel allocation.

The PVD calculator 424 may receive a predetermined threshold value for identifying whether the corresponding pixel is an edge region or a flat region. Here, if the PVD for the pixel is greater than a preset threshold (eg, 0), it corresponds to an edge area, and if the summed weight is less than the preset threshold (eg, 0), the flat area It may correspond to.

In this case, the selection of the threshold value may be selected with reference to a predetermined threshold value table and may be set to a preset default value.

The DMT generator 426 generates a DMT represented in FIG. 12 by recording at a corresponding position of a matrix generated using the PVD calculated for each color channel of each pixel.

The insertion capacity calculator 428 calculates the insertion capacity of each pixel with reference to the generated DMT. The insertion capacity of each pixel may be calculated in consideration of local image characteristics such as contrast or luminance.

The insertion capacity calculator 428 calculates the insertion capacity of the edge area and the flat area with reference to the generated DMT.

Thereafter, the insertion capacity calculator 428 allocates the capacity of the message to be inserted into the edge area and the flat area based on the ratio between the size of the message to be inserted into the image and the calculated insertion area of the edge area.

The insertion position calculator 430 generates a pseudo random number having a seed value as at least one of an image size, a message length, and a user input value, and uses the generated pseudo-random number to generate a message bit stream. Calculate the insertion position of.

The message inserter 440 inserts the message bit stream into the image according to the generated DMT and the calculated insertion position.

When the insertion of the message is completed, the correction unit 350 performs statistical correction for correcting the ratio of binary 0 and 1 with respect to the least significant bit of the pixel in which the message is not inserted.

When the statistical correction is completed, the transmitter 360 transmits the generated stego image to the message receiving apparatus 200 through a predetermined wired or wireless transmission channel.

The message receiving apparatus 200 receives a stego image through a predetermined transmission channel of a wired or wireless communication network, and extracts an inserted message using a DMT and a pseudo random number for the received stego image. In this case, the extracted message may be in an encrypted state. In this case, the message receiving apparatus 200 may decrypt the encrypted message using a pre-shared secret key.

Thereafter, when the decrypted message is compressed, the message receiving apparatus 200 may obtain the original message by releasing the compressed message using a predetermined decompression algorithm.

According to another embodiment of the present invention, the message providing device 100 inserts a predetermined error check code and error correction code into a generated stego image for detecting and correcting an error that may occur in a wired and wireless interval. It should be noted that it may further include a procedure for doing so.

5 and 6 are diagrams for explaining an adaptive message providing method using an image according to an embodiment of the present invention.

In operation S510, the message providing device 100 generates a message to be provided using an image. The message may be provided by a user's input, and may be input and stored in advance. In addition, the message may include text, images, audio and video.

In operation S520, the message providing apparatus 100 inserts more messages into the image, and compresses the messages in order to prevent deterioration of image quality of the Stego image generated after the insertion of the message.

In operation S530, the message providing device 100 may encrypt the message before insertion of the message in order to hide the characteristic pattern of the original message.

Some of the conventional steganography tools have the disadvantage of generating patterns that are dependent on stegoimages. Therefore, since the stagnalyst was able to extract the message by extracting the characteristic pattern of the stego image, the message providing device can encrypt the message to protect the message.

At this time, it will be apparent to those skilled in the art that the secret key used for encryption should be shared between the message providing device 100 and the message receiving device 200 before transmitting the stego image.

In particular, if proper encryption is applied to a message, the effect of hiding not only the meaning of the message but also the pattern dependent on the content of the message can be expected. In addition, the compression technique performed before encryption has the effect of randomizing the above-described specific patterns.

Thereafter, in operation S540, the message providing apparatus 100 performs a procedure of inserting an encrypted message into the cover message.

In the message providing apparatus according to the present invention, the following three basic concepts may be applied at the insertion stage in order to satisfy the non-cognition and maximize the message insertion capacity.

First, the message providing apparatus 100 according to the present invention divides the flat region and the edge region based on the color difference between each pixel and surrounding pixels of the image, and calculates the insertion capacity for each divided region.

Herein, the flat region means that the color difference between each pixel and the surrounding pixels-that is, the color change-is smaller than a predetermined threshold value, and the edge area means that the color difference between each pixel and the peripheral pixels has a predetermined threshold value. Means greater.

The human visual recognition system is characterized by more sensitive image changes due to secret data insertion in the flat region than in the edge region. That is, all images can be divided into flat areas and edge areas, where flat areas are sensitive to people's vision, while edge areas are less sensitive to people's vision.

Based on the characteristics of the human visual system as described above, the message providing apparatus 100 according to the present invention is characterized by inserting more secret data into the edge area than the flat area.

The insertion capacity for each area is calculated according to the ratio of the size of the encrypted message and the insertion capacity calculated corresponding to pixels corresponding to the edge area, and the calculated insertion capacity for each area is allocated to the edge area and the flat area, respectively.

For example, if an encrypted message has a length of 160 bytes and an insertable capacity in pixels corresponding to an edge area is 100 bytes, 100 and 60 byte messages may be inserted in the edge area and the flat area, respectively. Can be.

Second, the message providing apparatus 100 according to the present invention may select a position of a bit to be inserted into an image by using a pseudo random number generated through a predetermined seed value. Here, the predetermined seed value may be at least one of an image size, a message length, and a user input value.

Third, the insertion capacity of each pixel may be calculated in consideration of local image characteristics such as contrast or luminance.

This will be described in more detail with reference to FIG. 6.

In operation S550, the message providing apparatus 100 inserts a message using a difference mask table generated according to the characteristics of an image, hereinafter referred to as a 'difference mask table' and a pseudo random number, and then performs statistical correction. Can be done.

In operation S560, the message providing apparatus 100 generates a stego image when the statistical correction is completed.

In operation S570, the message providing apparatus 100 transmits the generated stego image to the corresponding message receiving apparatus 200.

6 is a view for explaining a message insertion method using an image according to an embodiment of the present invention described above.

Referring to FIG. 6, in operation S541 and S542, the message providing apparatus selects a predetermined threshold value and scans an image.

In operation S543, the message providing apparatus 100 classifies the scanned image for each color channel. The color channel can be divided into three colors, RGB (Red, Green, and Blue).

Thereafter, in operation S544, the message providing device 100 compares a color difference value between each pixel and neighboring pixels with the selected threshold value, and then calculates a PVD for each pixel.

In operation S545, the message providing device 100 generates a DMT using PVD for each pixel.

In operation S546, the message providing apparatus 100 calculates an insertion capacity of a message for each RGB color channel by referring to the DMT. In more detail, the message providing device 100 calculates the edge region insertion capacity EC _E and the flat region insertion capacity EC _S in the image, and between the size M of the message to be inserted and the calculated EC _E. ER _E is calculated. Here, ER _E is the following formula (1):

Can be calculated by

The message providing apparatus 100 compares the calculated ER _E with 1, if ER _E is less than or equal to 1, i.e., if the edge area insertion capacity is larger than the size of the message to be inserted, all messages are edged. Set to insert in the area. That is , EM _E = M; EM _S = 0 is set.

The message providing apparatus 100, if ER _E is greater than 1-that is, it is not possible to insert all the messages in the edge region-the following equation <2>:

By this, the number of bits κ to be inserted into the flat region is calculated.

Thereafter, in step S547, the message providing device 100 generates a pseudo random number having a seed value as at least one of an image size, a message length, and a user input value.

In operation S548, the message providing apparatus 100 calculates an insertion position of the message bit stream using the generated pseudo random number.

In operation S549, the message providing apparatus 100 checks whether the corresponding pixel of the image has an insertion capacity of an edge region with reference to the DMT.

If the insertion capacity of the edge area remains, the message providing device 100 inserts the corresponding message bit and subtracts the remaining edge area insertion capacity by the number of inserted bits.

If the insertion capacity of the edge area does not remain, the message providing device 100 checks whether the corresponding pixel has the insertion capacity of the flat area.

As a result of the check, when the insertion capacity of the flat region remains, the message providing device 100 inserts the calculated κ bit message and subtracts EM _S by k.

Thereafter, the message providing device 100 inserts all of the message into the edge region insertion capacity and / or the flat region insertion capacity, performs statistical correction, and then generates a stego image.

In the following description, a method of calculating a color difference between a specific pixel and an adjacent pixel on an image will be described in detail with reference to FIGS. 7 to 9.

7 and 8 illustrate a difference mask (DM) according to an embodiment of the present invention.

As shown in FIG. 7, a DM (Difference Mask) according to an embodiment of the present invention includes a target pixel 710 and eight peripheral pixels (Fig. 720 to 790) for calculating a color difference value. .

In this embodiment, it is assumed that one pixel information is composed of 24 bits, and 8 bits are allocated to each color channel.

Here, d _{i, j, which} is a sum of pixel value difference (SPVD) for each pixel, is represented by the following equation:

<Equation 3>

는 픽셀에서의 색상 차이 기준 값을 의미한다. Calculated by Where ω indicates the top four most significant bits of the corresponding pixel bit plan,

Denotes a color difference reference value in the pixel.

In the present embodiment, the top four MSBs of the pixel bit plan are limited to being used to calculate the color difference value, but are used to calculate the color difference value according to the non-cognizability and the insertion capacity required for the image starganography. Note that the number of MSBs may be different.

도 해당 스테카도그라피 기법의 비인지성 및 삽입 용량에 대한 시뮬레이션 결과에 따라 상이하게 적용될 수 있음을 주의해야 한다.In addition, the color difference reference value

It should be noted that this may be applied differently depending on the simulation results for the non-cognitive and insertion capacities of the corresponding stecardography technique.

d _{i , j} are calculated for each color channel, and the sum of pixel value difference for the edge pixels of the image, that is, the first row, first column, last row, and last column, as shown in FIG. 8. ) May not be calculated. The color difference calculation for the pixels included in the image may be performed from left to right and top to bottom, as shown in FIG. 8.

The calculated d _{i, j} for each color channel is compared with a predetermined threshold value δ to calculate a PVD corresponding to the corresponding color channel. The PVD calculated for each pixel is recorded at the corresponding position of the DMT.

9 is a view for explaining the use of the bit plan for each color channel according to an embodiment of the present invention.

In this embodiment, it is assumed that one pixel information is composed of 24 bits, and 8 bits are allocated to each color channel.

In general, human visual recognition systems are sensitive to changes in high frequency components and less sensitive to changes in low frequency components. Therefore, referring to FIG. 9, in the image steganography technique according to an embodiment of the present invention, the high frequency region 910 for each color channel, that is, b7 to b4- is used to calculate a color difference with surrounding pixels. Area 920-that is, b3 through b0- are used for message insertion.

Here, it should be noted that the boundary between the high frequency region and the low frequency region may be variously applied in consideration of non-cognition and insertion capacity. In addition, the number of low frequency region bits used for message insertion in the flat region and the edge region may be set differently.

10 and 11 are tables and graphs showing simulation results by the image steganography technique according to an embodiment of the present invention.

More specifically, FIGS. 10 and 11 are results of verifying whether distinguishing the high frequency region and the low frequency region based on the number of bits can maximize the message insertion capacity.

Here, the experiment was performed on 100 images commonly seen on the web, and the experimental result of FIG. 10 shows the insertion capacity according to the reference bit position for each of the four images, and FIG. 11 shows the position of the reference bit. The change in insertion capacity for 30 images is shown.

As shown in FIG. 10, in the case of a color channel having a length of 8 bits, it may be seen that the highest insertion capacity is obtained by dividing the high frequency region and the low frequency region based on the fourth bit.

Therefore, in the present embodiment, 4-MSB is used to calculate a color difference value with surrounding pixels based on the fourth bit, and 4-LSB is used for inserting a message. Since only 4-LSBs are used for message insertion, 4-MSBs maintain the same bit values for images and stegoimages. Accordingly, the message receiving apparatus 200 may generate a DMT by calculating a color difference value with neighboring pixels for each color channel of each pixel in the same manner as when inserting a message.

Hereinafter, an example of generating a DMT according to an embodiment of the present invention will be described in detail with reference to FIG. 12.

As shown in FIG. 12, the message providing device 100 calculates PVD for each color channel by comparing a color difference with neighboring pixels for each pixel of the scanned original image 1000 with a predetermined threshold value δ. The DMT 1010 is generated using the calculated PVD. Reference numeral 1030 illustrates an enlarged partial area 1020 of the DMT.

In general, it is necessary to scan an image three times in order to insert a message into the image by separating the RGB color channels. However, the image steganography technique according to the present invention generates a matrix DMT ( T _{i, j} ) having the same size as the image size after scanning only once without scanning the RGB channels separately and using them for message insertion. There is this.

In the image, if the pixel is larger than the given threshold value δ by calculating d _{i, j} for each color channel, the PVD is displayed at the corresponding index of the DMT matrix. Here, the PVD may be calculated by differently assigning a weight for each color channel. For example, if the R and B channels of the RGB color channels are selected as edge regions at the same time, and the weight for each color channel is set to R = 1, G = 2 and B = 4, the corresponding index value of the DMT matrix is 5 Is set to. That is, a message may be inserted into the 4-LSB of the R and B components.

13 to 15 are diagrams for explaining a method of selecting a message insertion position using a pseudo random number according to an embodiment of the present invention.

The conventional LSB insertion method of sequentially inserting messages in a fixed position has a problem that an attacker can easily extract the inserted message. In order to solve the above problem, the image stecanography technique according to an embodiment of the present invention has a feature of determining a message insertion position using a pseudo random number generated by using a predetermined seed value. Here, the predetermined seed value may be at least one of an image size, a message length, and a user input value.

Here, the message receiving apparatus 200 can know the insertion order of the messages only when the message length is known, and thus the original message can be extracted.

Positioning function SI (Selection Index) for inserting a message using a pseudo random number is represented by the following equation:

<Equation 4>

Can be defined by Here, m is at least one of an image size, a message length, and a user input value, r _i (m) is a pseudo random number generated from m as a seed, and t is a number of random numbers required to insert all messages.

S _i in Equation (4) represents the position of the i-th selected bit, and r _i (m) is a pseudo random number sequence generated using at least one of an image size, a message length, and a user input value as a seed. In order to ensure that the insertion position does not fall outside the range of the cover data, the range of pseudo random numbers [1, _lc ] should be generated within a range not exceeding the interval for embedding ( _c ) when the image is represented as a bit stream.

In this case, when the value of d _{i, j} of the insertion target pixel is not greater than the threshold δ, the generated pseudo random number may be discarded and the next pseudo random number may be generated.

Referring to FIG. 13, in the message insertion method using pseudo random numbers, it can be seen that a message is inserted in a random form on an image.

14 is a diagram illustrating a message insertion position when sequentially inserted without using pseudo random numbers.

As shown in Figure 14, the sequential insertion technique shows that messages are inserted sequentially from the top of the image.

15 is a diagram illustrating a message insertion position when using a pseudo random number according to an embodiment of the present invention.

As described above, since the message insertion position is generated within the stream length range of the image to be inserted, the insertion position is randomly distributed throughout the image as shown in FIG. 15.

If too many messages are inserted in a specific area of the image, false contours can be generated, and if inserted sequentially, they can be inserted at the top of the image as shown in FIG. You may not be able to.

However, as shown in FIG. 15, if a message is inserted at a position selected by a pseudo random number, the message is evenly distributed throughout the image, so that the image is hardly distorted and error spreading can be expected.

In addition, at least one of the image size, message length, and user input value to be inserted when generating a pseudo random number is used as a seed, so that the same inserted position can be found even when extracting the inserted message from the stego image.

16 is a mobile implementation demonstration screen using the steganography technique according to the present invention.

As illustrated in FIG. 16, according to a user selection, the mobile terminal outputs a predetermined message input screen including a message input window to the display unit (S1610).

Thereafter, the mobile terminal outputs a message received through a predetermined input means (for example, a keypad and a touch screen) to a message input window (S1620).

When the mobile terminal receives a predetermined control signal instructing to insert the input message (for example, when the OK button included in the message input screen is clicked), the mobile terminal inserts the input message in the image (S1630).

Here, the procedure of inserting the message input to the image may be performed according to the message insertion algorithm described in FIG.

When the message insertion is completed, the mobile terminal may output a predetermined guide message indicating that the message insertion is completed (that is, the Stego image is completed) on the display unit (S1640).

if. When the user is requested to extract a message from the stego image, the mobile terminal extracts the message from the stego image (S1650) and then outputs the extracted message to the display unit (S1660).

According to another embodiment of the present invention, the method may further include selecting an image to be used for message insertion from a plurality of images previously stored in the mobile terminal before step 1610.

In addition, the above-described embodiment according to FIG. 16 describes a procedure of generating a stego image and extracting a message from the stego image in the mobile terminal. The method may further include transmitting a message to the message receiving apparatus 200 through the transmission channel, and receiving the stego image through the corresponding transmission channel in the message receiving apparatus 200.

Here, the stego image generated by the message providing device 100 may be transmitted to the message receiving device 200 through a multimedia message service in the case of a mobile communication network.

The message receiving apparatus 200 determines whether or not the received image is a stego image, and then, in the case of the stego image, a predetermined interface guide message for checking whether to extract a message from the stego image, for example, "decoding. Press the OK button to print the display.

If the user wants to extract a message, the message receiving apparatus 200 may perform a procedure of extracting a message from the received stego image.

If the user does not want to immediately extract the message, the message receiving apparatus 200 may store the received stego image in a predetermined recording area.

Thereafter, the message receiving apparatus 200 may extract a pre-stored stego image and perform a message extraction procedure according to a predetermined user menu selection.

In addition, it should be noted that by adding an end-to-end stego image exchange procedure in a wired network such as the Internet, it may be variously applied in wired and wireless environments.

The message providing method using an image according to the present invention may be variously applied for the purpose of transmitting and receiving end-to-end security information in a wired / wireless integrated network. For example, the message providing method using the image according to the present invention can be variously applied to fields requiring strong security such as security and authentication procedures, e-commerce, finance, banking, and the like.

It is apparent to those skilled in the art that the above-described procedure shown in FIG. 16 is not possible in one embodiment, and can be applied to various fields using the stegonograph technique disclosed in the present invention.

Hereinafter, the simulation conditions and performance analysis results for the image steganography technique according to the present invention will be described briefly.

Here, the simulation conditions are divided into high, which is a sensitive area, when the value is greater than or equal to the threshold value δ, and low, which is a flat area, when the images are small. The image was divided into the whole region and the high region, and the message was inserted three bits in the low region, and the experiment was performed at δ = 4, 5, 6, and 7.

FIG. 17 is an image used in an experiment, and FIG. 18 shows an insertable capacity in high and low regions for each image according to the value of δ. Referring to FIG. 18, it can be seen that as the value of δ increases, the insertable dose decreases.

19 is a table showing MSE measurement results of the image steganography technique according to the present invention.

In the message providing apparatus, non-cognition means the image quality of a stego image generated by inserting a message into an image. That is, the difference between the two images can be expressed through a specific formula. To assess the level of non-cognition, we need to measure the visual difference between the image and the stego image.

Here, the level of non-cognition may be measured by Mean Square Equation (MSE) and Peak to Signal to Noise Ratio (PSNR) of the image and the stego image. Basically, the lower the MSE, the higher the PSNR, the higher the perception. Formulas for MSE and PSNR will be apparent to those skilled in the art, and thus detailed descriptions thereof will be omitted below.

Referring to FIG. 18 as a result of applying the image steganography technique according to the present invention to the entire area of the image, the table shown in FIG. 19 shows that the higher the insertion ratio, the higher the MSE.

20 is a table showing the PSNR measurement results of the image steganography technique according to the present invention.

Referring to FIG. 20, it is shown that as the δ increases, the PSNR also increases. In particular, it can be seen that the PSNR when inserted only in the High region is larger than when inserted in the entire region. Therefore, it can be seen that the steganography technique according to the present invention further increases non-cognition when inserted only in the High region.

Embodiments of the present invention include computer readable media including program instructions for performing various computer implemented operations. The computer readable medium may include program instructions, local data files, local data structures, or the like, alone or in combination. The media may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts.

Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical recording media such as CD-ROMs, DVDs, magnetic-optical media such as floppy disks, and ROM, RAM, flash memory, and the like. Hardware devices specifically configured to store and execute the same program instructions are included.

The medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like for transmitting a signal specifying a program command, a local data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 is a view for explaining a typical steganography model.

2 is a view for explaining a general steganography condition.

3 and 4 are diagrams for explaining the message providing apparatus according to an embodiment of the present invention.

5 is a diagram illustrating an adaptive message providing method using an image according to an embodiment of the present invention.

6 is a view for explaining a message insertion method using an image according to an embodiment of the present invention described above.

7 and 8 are diagrams for explaining a difference mask (DM) according to an embodiment of the present invention.

9 is a view for explaining the use of the bit plan for each color channel according to an embodiment of the present invention.

10 and 11 are tables and graphs showing simulation results by an image steganography technique according to an embodiment of the present invention.

12 is a diagram illustrating an example of generating a DMT according to an embodiment of the present invention.

13 to 15 are diagrams for explaining a method of selecting a message insertion position using a pseudo random number according to an embodiment of the present invention.

16 is a mobile implementation demonstration screen using the image steganography technique according to the present invention.

17 is a view for explaining an image used in the experiment of the image steganography technique according to the present invention.

18 is a graph of the insertion dose measurement results for the image steganography technique according to the present invention.

19 is a table of MSE measurement results of the image steganography technique according to the present invention.

20 is a PSNR measurement result table of the image steganography technique according to the present invention.

* Key Drawing

100: message providing device 200: message receiving device

310: message generating unit 320: compression unit

330: encryption unit 340: stego image generation unit

350: correction unit 360: transmission unit

410: image scanning unit 420: insertion capacity calculation unit

422: color channel separator 424: PVD calculator

426: DMT generator 428: insertion capacity calculator

430: Insertion position calculation unit 440: Message insertion unit

Claims (32)

In the message providing apparatus, The color channels of the image are divided into three colors of RGB (Red, Green, and Blue), and each color channel is used by using the color difference between each pixel and surrounding pixels and a preset threshold for each of the divided color channels. An insertion capacity calculator for calculating a message insertion capacity of each pixel of each pixel; And a message insertion unit for inserting the message into a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel of each color channel. The method of claim 1, The insertion capacity calculation unit, A color channel separator for dividing the image into color channels; A PVD calculator configured to calculate a pixel value difference (PVD) for each pixel by comparing a color difference obtained by comparing each pixel of the image with neighboring pixels for each color channel with the preset threshold value; And And an insertion capacity calculation unit for calculating a message insertion capacity of each pixel according to the pixel-specific PVD. The method of claim 2, The insertion capacity calculation unit, Further comprising a DMT generation unit for generating a DMT (Difference Mask Table) which is a matrix generated by using the pixel-specific PVD, The insertion capacity calculator calculates a message insertion capacity of each pixel with reference to the generated DMT. The method of claim 2, The insertion capacity calculation unit compares the PVD for each pixel with a preset threshold and divides it into an edge area and a smoothing area, and the insertion capacity for each color channel for the divided edge area and the flat area. Message providing apparatus using an image, characterized in that for calculating. The method of claim 4, wherein The insertion capacity calculator determines an size of the message to be inserted into each of the edge area and the flat area by comparing the size of the message with the insertion capacity calculated for the edge area. . The method of claim 1, And a position calculator for calculating a position at which the message is to be inserted using a pseudo random number generated according to a predetermined seed value. The method of claim 6, And the seed value is at least one of the image size, the message length, and a user input value. The method of claim 1, Further comprising a compressor for compressing the message using a predetermined compression algorithm, The message inserter inserts the compressed message into a color channel of a predetermined pixel included in the image. The method of claim 1, Further comprising an encryption unit for encrypting the message using a predetermined encryption key, The message inserter inserts the encrypted message into a color channel of a predetermined pixel included in the image. The method of claim 1, And a statistical corrector configured to correct a ratio of binary zeros or ones to the least significant bits of pixels in which the message is not inserted. The method of claim 1, And a transmitter configured to transmit the image into which the message is inserted through a communication network. In the message providing method, The color channels of the image are divided into three colors of RGB (Red, Green, and Blue), and each color channel is used by using the color difference between each pixel and surrounding pixels and a preset threshold for each of the divided color channels. Calculating a message insertion capacity of each pixel; And And inserting the message into a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel of each color channel. The method of claim 12, The message is a message providing method using an image including at least one of the form of text, voice, image, video. The method of claim 12, And the information bit for each color channel is N bits (N is a natural number of at least 8). The method of claim 14, Inserting the message The image is characterized by inserting the message using a predetermined low frequency component bit (where the low frequency component bit is a predetermined bit starting from the least significant bit (LSB)) among the information bits of the color channel. How to provide a message. The method of claim 12, The color channel includes a red (R) color channel, a green (G) color channel and a blue (B) color channel. The method of claim 12, The step of calculating the insertion dose Dividing the image by color channels; Calculating a PVD for each pixel by comparing a color difference obtained by comparing each pixel of the image with neighboring pixels for each color channel with the preset threshold value; And And calculating a message insertion capacity of each pixel according to the pixel-specific PVD. The method of claim 17, The step of calculating the PVD Weighting each of the respective pixel color channel P ^{n -} wherein and P is a natural number of 2 or more, n is a natural number including 0, using the allocated different n values to each other for each color channel, and the PVD using the integrated value of the weight Message providing method using the image, characterized in that calculating. The method of claim 17, The step of calculating the insertion dose, Generating a difference mask table (DMT), which is a matrix generated by summing weights of respective color channels of each pixel, The calculating of the insertion capacity may include calculating a message insertion capacity of each pixel with reference to the generated DMT. The method of claim 17, The step of calculating the insertion dose Dividing the PVD calculated for each pixel into an edge area and a smoothing area by comparing the calculated PVD with a preset threshold value; And And calculating the insertion capacity for each of the color channels for the divided edge region and the flat region. The method of claim 20, The step of calculating the insertion dose Comparing the size of the message with the insertion capacity calculated for the edge region; And And determining the size of the message to be inserted into each of the edge area and the flat area when the size of the message is larger than the insertion capacity of the edge area. The method of claim 12, The color difference d _{i, j} from the surrounding pixel is represented by the following equation:

Where ω is at least one high frequency component bit used to calculate the color difference among the corresponding pixel bit plans, ε is the color difference reference value in the pixel, i is the row where the pixel of the image is located, j is A column in which an image pixel is located, x (i, j), is a color value of the pixel. The method of claim 12, And calculating a position at which the message is to be inserted using a pseudo random number generated according to a predetermined seed value. The method of claim 12, Before calculating the message insertion capacity And compressing the message by using a predetermined compression algorithm. The method of claim 12, Before calculating the message insertion capacity And encrypting the message using a predetermined encryption key. The method of claim 12, Before calculating the message insertion capacity The message providing method using the image further comprises the step of inputting the image or the message. The method of claim 12, After inserting the message, And correcting a ratio of binary zeros or ones to the least significant bit of the pixel in which the message is not inserted. The method of claim 12, After inserting the message, And transmitting the image in which the message is inserted through a communication network. In the message providing method using a communication terminal, Displaying an image on a message input window; Outputting a message to the message input window; Inserting the message into the image; Including the step of transmitting the image in which the message is inserted, Inserting the message is The color channels of the image are divided into three colors of RGB (Red, Green, and Blue), and each color channel is used by using the color difference between each pixel and surrounding pixels and a preset threshold for each of the divided color channels. Calculating a message insertion capacity of each pixel; And And inserting the message into a color channel of a predetermined pixel included in the image according to the calculated message insertion capacity of each pixel of each color channel. 30. The method of claim 29, The step of displaying an image on the message input window And selecting an image to be used to insert the message according to a predetermined user menu selection. 30. The method of claim 29, The step of outputting a message in the message input window The message is input or the stored message is extracted and output, characterized in that for outputting a message using the image. The method of claim 29 And the image in which the transmitted message is inserted is transmitted through a multimedia message service.

Images