РОЗРОБКА СТЕГАНОГРАФІЧНОГО МЕТОДУ ВБУДОВИ БІНАРНОГО ЦИФРОВОГО ВОДЯНОГО ЗНАКУ В ЗОБРАЖЕННЯ НА ОСНОВІ ДИСКРЕТНОГО КОСИНУСНОГО ПЕРЕТВОРЕННЯ

This paper describes a steganographic method of embedding a binary digital watermark into the mid-frequency coefficients of discrete cosine transform of a digital image. One of the mid-frequency coefficients of the two-color components of a color image is used to embed the digital watermark: one color component is used to embed a secret coefficient which reflects changes in the image and helps to improve the quality of the extracted digital watermark after applying noise to the stego. The second color component of the container is used for embedding of the digital watermark. The proposed method involves the automatic selection of color components of the container for embedding the digital watermark and its pre-processing to increase the distance between its elements. The article contains the main steps of embedding and extracting of a digital watermark, as well as the results of computational experiments aimed at evaluating the efficiency of the steganographic method, and comparing the results with modern analogues. The efficiency of the steganographic method is evaluated by the indicator of visual quality PSNR of stego and various indicators of message extraction. Resistance to attacks is evaluated by indicators of extraction of information from the modified stego. The paper analyzes the developed method when embedding some secret coefficient equal to 20 and the digital watermark into the coefficient (5.5) of the discrete cosine transform of each 8»8 block of digital image is carried out. The results of computational experiments showed the high visual quality of the received stegan messages (PSNR is 50-58 dB) and the resistance of this method to noise, namely: multiplicative, Poisson, Gaussian and "salt and pepper". In the case of Poisson noise, the digital watermark is extracted almost without loss, the quality of extraction of the digital watermark was not lower than 0.97. [ABSTRACT FROM AUTHOR]