A high capacity reversible steganography method based on lsb mapping area for hiding lossy images into images

Steganography is a data hiding method in an innocent media to prevent initial observations from third parties. Thus, third parties are not aware of the presence of the secret data when steganography is concerned. Steganography can be applied to image, video, audio or text files. In this thesis, a set of new data hiding methods have been proposed for still images. The first three are irreversible methods which divide cover media into equal mapping areas to match the bits of secret data. The mapping areas are tested whether they are suitable for hiding the bits of the secret data. If so, the location of the hidden bits are marked. Since the secret data are represented by existing bits in the cover file, cover bits can be changed only during marking procedures. The next proposed three methods are reversible by which high capacity lossy images can be hidden into images. In reversible methods, the mapping areas are created in determined coded ranges. Proposed methods try to embed as much as possible secret data with a minimum change in cover bits. The method proposed have been tested comprehensively against well-known steganalysis algorithms using 150 image files embedded with secret data then the image distortion parameters have been evaluated. The proposed reversible methods have achieved two times better capacity and %10 lower distortion rate as PSNR compared to the studies in the literature.