Security Of Information Hiding

As a new branch of information security, information hiding technology including digital watermarking and steganography aims to protect intellectual property rights of multimedia contents and to send secret messages under the cover of a carrier signal. The capability of resisting malicious attacks, i.e., security, is a key requirement in information hiding. While numerous progresses are being made in watermarking and steganographic techniques against various attacks, the opposite side of the combat is also striving to advance their attack strategies in order to defeat the effort of information hider. This thesis summarizes the results obtained in the author's investigation into various aspects of information hiding both in digital watermarking and steganography/steganalysis. The study has been carried out in view of the information warfare with the data hider on one side, and the attacker/steganalyst on the other.The research achievements on information hiding security are classified into the following four categories.The first is a study on a number of basic theoretical problems in information hiding. Based on a comparison of the performance of two popular techniques, theoretical analysis and numerical experiments show that the method of addition is suitable for watermark embedding into high frequency components, whereas the quantization technique is more appropriate for embedding into low frequency components. An improved approach based on sequence addition is proposed that effectively exploits the information carrying capability of each binary sequence by mapping a number of bits to a single sequence picked up from an orthogonal set, leading to significant performance improvements. On the other hand, embedding capacity of the quantization method in the presence of attack and the optimal embedding strategy are studied. It is shown that the maximum attainable payload is determined by the size of cover media and the ratio between distortion levels caused by the data-hider and the active attacker respectively.The second category is the development of watermarking algorithm or protocol capable of withstanding hostile attacks. It is demonstrated that, by randomly selecting watermark signals, which are mutually independent even derived from a single key, the inserter-based attack can no longer remove the legitimate mark. In addition, with this new method, a trace is left if the product was maliciously tampered. It is shown that, even with a noninvertible watermarking algorithm or an asymmetric watermarking protocol, it is still possible to effect an invertibility attack, which relies on a forged watermarking algorithm, a counterfeit mark, and a fake key. As a solution, a secure watermarking protocol is presented, which establishes correlation between the watermarking algorithm and the embedded mark. The proposed protocol and algorithm can be integrated into a watermarking system.The third is to propose several secure steganographic schemes used in cover media with different formats. For an uncompressed cover image, a novel steganographic scheme is described . which avoids asymmetry inherent in conventional LSB embedding techniques and minimizes the histogram abnormality so that both histogram-based and asymmetry-based attacks are disabled. It is also shown that some peculiar colors can cause vulnerability of the optimal parity assignment (OPA) steganography in palette images. Based on this analysis, an advanced steganography is developed that, while keeping the advantage of low distortion of the OPA, avoids theabove-mentioned peculiar colors and makes use of the local properties in the host image to improve the security of embedded information. In another data hiding technique for JPEG cover image, when AC DCT coefficients with non-zero values are used to carry secret bits, the DCT coefficient histogram and blockiness property are reserved. In this way, the histogram-based and blockiness-based steganalyses are effectively defeated.The last category is steganographic and steganalytic techniques based on the hu...