Research On Data Hiding Scheme Based On Modulus Function

Information hiding is one of the important aspects of current information security research. As one of the main branches of information hiding, more and more attention has been paid to steganography by researchers at home and broad. By making use of the redundant information in digital products, such as video、text、 photo, stegranography will embed the secret information into the carrier, and so to guarantee the security of secret messages transmission. The paper mainly researched the stegranographic algorithms based on modulus function and pixel-value differencing. And the purpose of the research is that proposed algorithms can achieve higher embedding capacity as well as the stego-image keeps a better visual quality. The main contents together with innovation points of this thesis are as follows:(1)A novel steganographic scheme based on modulus function is analysed. After embedding the secret information in the image by using this algorithm, the pixel change range is large. On basis of the shortcoming, improved algorithm is proposed which adopts new method of creating pixel group. And then the range of most pixels changes from [0,2n-1] to [0,2n-1]. Imperceptibility、embedding capacity and security are compared in experiments to analyse the original algorithm and the improved. Simulation results show that the proposed method effectively improves the imperceptibility and the ability resisting RS attack of secret imformation.(2)A steganographic method for images by pixel-value differencing is researched. In order to avoid the pixel-value which is embedded secret data is greater than255or less than0, pixel-value overflow inspection is carried out before embedding data by this algorithm. In theory, the paper deduces the method of pixel-value overflow checking and verifies the validity of the deduced theory. The experiment is carried on after the analysis of the algorithm, and the results show PSNR of images, such as Lena, when embedding capacity are different.(3)By using the steganographic method of pixel-value differencing, differencing of pixel blocks are divided into six intervals, namely R1～R6, and the embedded data capacity is up to the interval which pixel-value differencing belongs to. The experimental results sugguest most of the differencing belongs to R1、R2. As a result, with the purpose of improving embedding capacity, the algorithm of pixel-value differencing can be combined with the improved modulus function algorithm. That is to say, embed secret data into two-pixel blocks whose differences fall within R1and R2with improved algorithm, and each pixel is embedded3bits, while other ranges with pixel-value differencing algorithm. The experiments choose four images as carrier, such as Lena、Elaine、Peppers and Baboon, the thesis analyzes the change of embedding capacity in detail. The experiment indicates that the steganography based on pixel-value differencing and improved modulus function greatly improves the embedding capacity, and image quality declines but accepted by human eyes.