Розробка теоретичних основ методу відокремлення цифрового зображення, збереженого у форматі без втрат, від зображення, збереженого із втратами. DEVELOPMENT OF THEORETICAL BASIS OF THE METHOD OF SEPARATING DIGITAL IMAGE SAVED IN A FORMAT WITHOUT LOSSES FROM A IMAGE SAVED WITH LOSSES
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Date
2018
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Abstract
Information integrity is one of the main properties of the information security object. The use of information content is often possible only if its integrity is not compromised. The task of identifying violations of the integrity of an information remains relevant one. Particular difficulties arise if the violation of the integrity of information content leads to its very minor disturbances. Today, digital images, video, digital audio are often used as information contents. The work is devoted to the analysis of digital images. Currently, the storage and transmission of digital images is carried out in two fundamentally different forms – with losses and without losses. Unauthorized actions on the image often lead to a difference in the format of the original image from the one whose integrity is violated. This is typical for a steganography, when the organization of a hidden communication channel uses the steganographic method, which is not resistant to attacks against the embedded message, and the image in a lossy format acts as a container. Establishing the fact of a format change here is a pointer to the transformation of the image, to the violation of its integrity, can be used for the purposes of steganoanalysis. Paper developed a theoretical basis of the method of separaton of a digital image, which was originally stored in a lossless format, from that which was saved to a lossless format from a lossy format. The basis of the future method is the analysis of the normalized separation of the maximum singular numbers of blocks of the image matrix. The blocks are obtained as a result of the standard partition of the matrix. During the examination, the image is re-stored in a lossy format (Jpeg) with quality factors. The curve reflecting the dependence of the number of blocks of a digital image for which the normalized separation of the maximum singular numbers does not change after being saved in Jpeg as a function of the quality factor is analyzed. During development, the concept of a pronounced local maximum of a function was introduced and formalized. The existence/absence of a pronounced local maximum on the mentioned curve is a pointer to the format of the original image with loss/ lossless.
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цифрове зображення, порушення цілісності, формат із втратами, формат без втрат, сингулярне число, відокремленість сингулярного числа, digital image, integrity violation, lossy format, lossless format, sin-gular number, singular number separation