RU2407216C1 - Method for message integration into digital image - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: method is based on series of information bits match with bits in bytes of colour presentation, with change of least significant bits in initial image and requiring minimum correction of statistical characteristics of only least significant bits, as a result of accidental nature of matches. Least significant bit is replaced in bytes in initial digital image, besides, flag value "one" is assigned to least significant bit in bytes of initial digital image, if part of digital image signal byte bits and message signal bits match, or flag value "zero" is assigned in case of non-match, at the same time correction of statistics of distribution of least significant bits is made by their remaining part, which is not used as flag values.

EFFECT: possibility to store and transfer large volumes of confidential information.

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Description

The invention relates to the field of steganography, and in particular to methods of embedding messages in digital images, and can be used to organize hidden storage and transmission of confidential information through open communication channels, as well as digital watermarks.

Known methods for steganographic protection of information based on the introduction of additional information in raster images by replacing the least significant bits in bytes of the color representation of the original image with bits of added information (See Bender W., Gruhl D, Morimoto N., Lu A., Techniques for data hiding , IBM system journal, vol. 35 (3 & 4), p. 313-336, 1996. RF patent No. 2002135272, publ. 10.07.2004).

The main disadvantage of such methods is the low efficiency of information protection, since in this case, changes lead to a distortion of a number of statistical parameters of processed images, which can be detected by statistical analysis methods (See Westfeld A., Pfitzmann A. Attacks on Steganographic System. Breaking the Steganographic Utilities EzStego, Jsteg, Steganos, and S-Tools - and Some Lessons Learned // Proceeding of the Workshop on Information Hiding 1999 - 16 p.). Currently, such analysis methods as visual steganoanalysis, analysis of series lengths, analysis of the number of transitions, estimation of entropy, analysis of histograms based on the χ ² criterion are effectively used.

There is also a method of embedding additional information in digital images, in which to counter some analysis methods when recording information, only a part of the least significant bits in bytes of the color representation of the original image is used, the remaining bits are used for subsequent correction of the most important statistical parameters (See Provos N. Defending Against Statistical Steganalysis, Proceeding of the 10 USENIX Security Symposium, 2001, p. 323-335).

The disadvantage of this method is that the corrective changes lead to additional distortion of the digital image and reduce the bandwidth of the stegano channel using part of the free space for the corrective information. In addition, corrective corrections aimed at counteracting any of the methods of statistical analysis by correcting one of the parameters can lead to even more distortion of other parameters and, as a result, to more likely detection of a hidden channel by other analysis methods. In particular, the distortions introduced by the introduction of additional information and corrective changes when using this method can be noticeable when conducting a visual analysis of the bit layers of the resulting image.

The disadvantages of the above methods of embedding information in raster images should also include the fact that only the least significant bits of the bytes of the color representation are used for embedding information, which does not allow the full use of the entire amount of image data.

The closest in technical essence to the claimed invention (prototype) is a method of introducing additional information into digital images (See RF Patent No. 2285844, publ. 11/27/2006, BI No. 33), which consists in the fact that the original digital image is laid out on bit layers , to record additional information, one of the obtained bit layers is selected, which is presented in the form of a bit sequence, additional information is recorded using a code, and in this bit sequence the bits put on the borders of all transitions of identical sequences of zeros and ones, are replaced in accordance with the bits of the recorded additional information, the remaining bits of the underlying bit layers, if necessary, are used to correct the original image or to record other additional information.

The disadvantage of this method is the need for correction of statistical characteristics, which leads to an increase in image processing time, as well as to a decrease in the amount of embedded information. At the same time, an increase in the volume of embedded information is achieved through the use of high-order bit layers, which leads to an even greater change in the original image.

The technical result to which the invention is directed is to develop a method of embedding a message in a digital image, providing the ability to store and transmit large amounts of confidential information based on a series of coincidence of information bits with bits in color representation bytes, when only the least significant changes in the original image ( flag) bits and requiring minimal correction of statistical characteristics of only the least significant bits, due to random coincidences.

The technical result is achieved due to the fact that in the known method of embedding additional information in a digital image, which consists in replacing individual bits in bytes of the original digital image with embedded information bits, the least significant bit in the bytes of the original digital image is assigned the flag value “one” when part of the bits coincides bytes of the digital image signal and bits of the message signal, or the flag value “zero” in case of mismatch, while adjusting the distribution statistics least significant bits are produced for the rest of them, not used as flag values.

Thanks to the new combination of essential features in the method, it is possible to embed large volumes of confidential information with minimal change in the original image and requiring minimal correction of statistical characteristics.

The analysis of the prior art made it possible to establish that analogues that are characterized by a combination of features identical to all the features of the claimed technical solution are absent, which indicates the compliance of the claimed method with the condition of patentability “novelty”.

Search results for known solutions in this and related fields of technology in order to identify features that match the distinctive features of the claimed object from the prototype showed that they do not follow explicitly from the prior art. The prior art also did not reveal the fame of the distinctive essential features that determine the same technical result, which was achieved in the claimed method. Therefore, the claimed invention meets the condition of patentability "inventive step".

The claimed method is illustrated by drawings, which show:

figure 1 - General diagram of a device that implements a method of embedding a message in a digital image;

figure 2 is a schematic logical diagram of a device that implements a method of embedding a message in a digital image,

figure 3 - General diagram of a device that implements a method for retrieving a message.

A device that implements the claimed method, the General scheme of which is presented in figure 1, and the circuit diagram in figure 2, works as follows.

The digital image signal (container) 1 is sequentially bit-wise fed to the input of block 2, a serial-parallel converter, consisting of an 8-bit shift register (chip KR1554IR24) and an 8-bit buffer register (chip KR1554IR22). The T1 clock pulses are fed to the input of block 2 and to the input of block 5 - the control unit, including two 4-bit binary synchronous counters (KP1554IE23 chip), two D-flip-flops (KP1554TM2 chip), four 2I-NOT elements (KR1554LAZ chip) and four element 2I (chip KR1554LI1). The message signal is fed sequentially bit by bit to the input of block 4 — the block of storage of the embedded bits of the message, consisting of an 8-bit shift register (chip KR1554IR24).

With the arrival of the 8th clock pulse in block 2 (the output of the 8-bit shift register is the KR1554IR24 chip), a container signal is generated, and at the output of the control unit (the output Q4 of the 4-bit binary synchronous counter - the KR1554IE23 chip), a signal is generated that allows the container signal to be transmitted in parallel form, to the output of block 2 (the output of the 8-bit buffer register is the KR1554IR22 chip) and to the input of block 7, the block of storage of the stegocontainer signal byte is the 8-bit buffer register (the KR1554IR2222 chip). From the output of block 4 to the input of block 6 (a comparison block including 4 elements 2 OR - a comparator (chip КР1554ЛП5), 4 elements 2 OR-NOT (chip КР1554LE1)) two bits of the embedded message are sent, which are compared with 6 and 7 (by number from 1 to 8) bits, respectively, of the container signal generated at the output of block 2. If the bits of the container signal and the bits of the embedded message signal match in pairs, the eighth bit of the container signal in block 7 is set to the state of a logical unit. Reading the byte of the signal of the container from the input to the output of block 7 is carried out on the trailing edge of the 8th clock pulse. At the same time, the 4-bit binary synchronous counter of block 5 is reset to zero (chip KR1554IE23).

If the eighth bit of the container signal in block 7 is set to the state of a logical unit, a signal is generated to read two successive bits of the signal of the embedded message in block 4. A signal allowing reading of the next bits of the signal of the embedded message is generated in block 5 (D-trigger and element 2I) At the output of the counter Q2, through two clock pulses, the D-flip-flop signal is generated and the reading process is stopped for another comparison.

If the eighth bit of the container signal in block 7 is set to a logical zero state (pairwise mismatch of the container signal bits and the embedded message), the byte of the stegocontainer signal is read from the input to the output of block 7 by the trailing edge of the 8th clock pulse. At the same time, the 4-bit binary synchronous counter of block 5 (chip KR1554IE23) is reset to zero. However, the signal allowing the reading of the next bits of the signal of the embedded message in block 5 (D-trigger and element 2I) is not generated and the signal bits of the next byte of the container are compared with previously recorded bits of the embedded message signal.

The extraction of the message embedded in the digital image according to the method, the general scheme of which is presented in figure 1, is carried out in accordance with the scheme presented in figure 3, in the following order.

The digital image signal with a built-in message (stegocontainer) block 1 is sequentially bitwise fed to the input of block 2 - a serial-parallel converter. Clock pulses from block 6 - a clock pulse generator is fed to the input of block 2 and to the input of block 5 - control block.

With the arrival of the 8th clock pulse in block 2, a stegocontainer signal is generated, and at the output of block 5, a signal is generated that allows the signal transmission of the stegocontainer in parallel to the output of block 2.

The eighth bit of the generated byte of the signal of the stegocontainer is fed to the input of block 5, where it is compared with a logical unit and, in case of coincidence, a signal is generated that permits reading 6 and 7 (at a number from 1 to 8) bits of the signal of the stegocontainer, which are input to block 3 - block retrieve and store the embedded message.

If necessary, statistics are corrected for the unused eighth bits of the stegocontainer bytes.

The tests performed showed a high stability of the method of embedding a message in a digital image against visual analysis and statistical methods for analyzing the distributions of the least significant bits of the image. During the tests, the relative amount of embedded data in some cases amounted to 10% of the volume of the original digital image, while maintaining the visual quality of the latter. To ensure the greatest efficiency of embedding a message in a digital image, the latter is given the character of a pseudo-random sequence. The most effective is the use of the proposed method of embedding information together with scrambling and efficient coding algorithms.

Claims (1)

A method of embedding a message in a digital image, which consists in replacing the least significant bit in bytes of the original digital image, characterized in that the least significant bit in the bytes of the original digital image is assigned a flag value of "one" when the bit part of the digital image signal byte and the message signal bits match either flag value “zero” when there is a mismatch, while the statistics of the distribution of the least significant bits are adjusted for the remaining part that is not used as TBE flag values.

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