Study On The Theory And Algorithm Of Information Hiding

Information hiding technology has broad applications, and has been paid more and more attention. The theory and algorithm of information hiding are deeply studied in the paper, including information hiding capacity, watermark detection, watermark algorithm with strong robustness, self-embedding fragile watermark algorithm, multi-purpose dual watermark algorithm and reversible watermark algorithm.The attributions of the paper are:(1) With respect to information hiding system under passive attacks, a concrete statistical model of information hiding system is built and its performance is analyzed, including security, distortion distance metric, and channel capacity. The solution to channel capacity can be regarded, subjected to average hamming distortion distance and average security coefficient, as an optimization problem. As long as the required parameters are given, the optimization problem of channel capacity will be easily solved by using optimization theory. Finally, the channel capacity of statistical model is derived on the condition that both original cover sequence and secret information sequence obey to uniform distributions.(2) Quantized projection (QP) technology is the version of quantization index modulation (QIM) working in the projection domain. It essentially belongs to a double-sided additive embedder. The concept of sign quantized projection (SQP) is proposed in the paper, which differs from the conventional QP in working as a single-sided embedder. Theoretical analysis reveals that SQP has the same probability of miss and probability of false alarm as QP. In the meanwhile, the document-to-watermark ratio (DWR) of SQP is less than its counterpart of QP by 10log10(1+γ)dB.(3) The print-and-scan process always brings a lot disturbance to the original digital image, therefore the watermarking algorithm for print-and-scan process desires extremely high robustness. At present, most robust watermarking algorithms can't resist the print-and-scan process. A robust zero-watermark algorithm for print-and-scan process is proposed in the paper, based on the energy aggregation effect of discrete wavelet transformation's (DWT) low frequency band and the stability of singular value decomposition's (SVD) singular values. It conducts DWT with the original image, divides its low frequency band into blocks, and conducts SVD with every block. Zero-watermark is derived by judging the numerical relationship between two biggest singular values from adjacent blocks. The experimental results show that it has the ability to resist desynchronization attacks and print-and-scan process.(4) At present, the tamper sensitivity of some fragile watermark algorithms needs to be improved. Moreover, some fragile watermark algorithms can't distinguish image's malicious tamper type. A self-embedding fragile authentication watermark algorithm based on SVD and chaotic mapping is proposed, trying to apply chaotic mapping's initial value sensitivity to tamper detection and distinguish image's malicious tamper type. SVD is carried out on each image block, and authentication watermark is produced by using Logistic chaotic mapping. Then Logistic chaotic mapping is used to design a mapping function defined on two separate blocks, and authentication watermark sequence is embedded into the corresponding mapping block's least significant bit (LSB). The experimental results show that the algorithm is not only very sensitive to tamper, but also resists collage attack and distinguishes image content tamper from watermark tamper.(5) The single watermark algorithms always merely have single function. In order to overcome the drawback, a multi-purpose dual watermark algorithm is proposed in the paper, taking advantage of the stability of singular values. It divides the original image into several blocks, and inserts robust watermark into their singular values. Then it inserts the fragile watermark into LSB in the space domain of previous watermarked image. Moreover, it designs a rule to distinguish malicious tamper from unintentional tamper. It tests not only robust watermark's robustness towards attacks, but also fragile watermark's influence towards robustness as well as the ability to tamper detection and localization. The experimental results show that the robust watermark possesses strong robustness to resist attacks, and that the fragile watermark is very sensitive to tamper and has good accuracy of tamper localization. Therefore it can achieve copyright protection and content authentication at the same time.(6) The concept of dynamic distortion-compensated quantization index modulation (Dynamic DC-QIM) is proposed, which differs from the conventional DC-QIM in whether or not quantization step size and DC parameter are changeable. Firstly, the condition satisfying the reversibility of dynamic DC-QIM is deduced. Then, the allowable range of dynamic DC parameter is derived. Finally, the procedure of reversible watermark algorithm based on dynamic DC-QIM is designed. Its data hiding rate can achieve as high as lbpp in a single iteration, higher than its former counterparts. Furthermore, the use of dynamic characteristic is in favor of preventing its parameters from being disclosed. Experimental results show that it not only accurately decodes the secret information, but also perfectly restores the original cover, regardless of initial conditions.