Volume increasing of secret message in a fixed graphical stego container based on intelligent image analysis

Abstract

The paper considers methods of edge pixel selection based on Roberts, Previtt, and Sobel operators, as well as technologies of cellular automata to increase the volume of the implemented secret message. Based on the methods used, templates with selected pixels were formed, into the codes of which secret message bits were embedded. The templates were formed using threshold additional processing, which allowed to select the optimal threshold for the selection of the corresponding pixels of the image of the container. Thresholds ranging from 100 to 300 were selected for the Roberts operator, and thresholds ranging from 1,000,000 to 15,000,000 were selected for the Previtt and Sobel operator. To select pixels based on cell technology, four cell neighborhood shapes were used for binary and color imaging. Experimental studies were performed for all methods of pixel selection, which made it possible to determine the optimal numerical threshold, as well as the number of lower bits of each selected pixel to implement the bits of the secret message. It has been experimentally established that for all methods, except for the two lower bits of the code of each pixel, the bits of the secret message are also embedded in the four lower bits of each byte of code of the selected pixel, which significantly increases the volume of the embedded message. When using two lower bits of all pixels and four lower bits of selected pixels for many templates, no change in the visual images of the containers was observed. Using the fifth lower bit in each byte of the selected pixel code to enter the secret bit results in significant distortion of the visual picture. The experiments were performed for different brightness thresholds during binarization. In total, six additional secret bits were added to the code of each selected pixel. For the efficiency of the experiments, bit sequences containing only one zero, one unit, and randomly generated bit sequences were introduced into the containers.