Use of the Normalized Gap of Maximum Singular Value of the Image Block to Evaluate the Capacity of the Steganographic Channel

Abstract

The Least Significant Bit (LSB) method is one of the most widespread and demanded steganographic methods nowadays. Detection and decoding the hidden information, embedded in a container using the LSB, is a challenging task, in particular, in conditions of low capacity of the hidden communication channel. The existing steganalysis algorithms developed to detect the LSB, as a rule, solve the main problem of steganalysis - the detection of a hidden communication channel. However, the problem of the additional information recovery remains unfulfilled. The important step in solving this problem is the evaluation of the hidden (steganographic) channel capacity. In the current work, a digital image is used as container. All the results obtained can also be applied to digital video, which is considered as a sequence of frames. The aim of the work is to get estimates for the value of the capacity of the hidden communication channel, formed by the LSB method. To achieve the aim of the work the following studies carried out: performed additional in-depth investigation of properties of the normalized gap of the maximum singular value of non-intersecting image blocks, obtained by standard splitting; studied properties of a discrete function y(QF), that determines the number of image blocks in which the normalized gap of maximum singular value increases when the image is re-saved to lossy format with quality factor QF. As a result of the research, the estimates of the value of the capacity of the hidden communication channel, created using the LSB method and based on a container in a lossy format, were obtained.