Study On Digital Watermarking Algorithm Based On Chaos

With the popularization of the Internet and multimedia technology,all the digital information(such as digital image,video etc.) in the Internet are facing the security problem. How to protect the copyright of the digital products becomes one of the most attractive research issues. The digital watermarking technique is just an effective way to solve this problem. Digital watermarking can protect the benefit of the copyright owner by inserting an invisible mark into the digital information and detecting them with special methods in appropriate time. In addition, digital watermarking technique has also used to some other research fields except the copyright protecting. Chaotic sequences have good features such as noise-like, unpredictable yet deterministic orbits and sensitivity to initial condition and parameters. So chaotic signals are suitable for digital watermarking application. This paper selects digital image as watermarking objects, chaotic sequences generated by the logistic map as watermarking, and chooses spatial domain, DCT domain to investigate watermark algorithm. The main contributions in this paper are as follows:â‘  This paper introduces chaotic sequences to the watermark systems as watermarking. The chaotic sequences are sensitive to initial parameters. Different initial parameters will generate different sequences, which can ensure digital watermarking unique. So it is almost impossible for an attacker to forge the watermark. At the meantime, the generation of chaotic sequences is very simple because different initial conditions in the attractive region will lead to different chaotic sequences, which makes it possible for chaotic sequences to be applied to the occasions with abundant watermark to be needed.â‘¡ An algorithm based on iterative blending on spatial domain is proposed. A chaotic sequence is mapped to a gray image. The embedding of the watermark is done by means of the iterative blending approach. Computer simulations show that the embedded watermark is imperceptive. In order to enhance the robustness, the Peano scanning technique is used to mapping process, which maintains the low-pass property of the watermark signal.â‘¢ A crop-resistant digital watermarking algorithm on the spatial domain is also proposed. Some pixels are sought out from the original image according to a random sequence generated by a chaotic system, which makes this algorithm robust to cropping attack because of the random of the chaotic sequence. The watermark is adaptively embedded into those pixels according to the characteristic of the human visual system (HVS). Furthermore, it is also practical because the original image is not required in the detecting process.â‘£ On the DCT domain, an adaptive algorithm based on DCT blocks is presented. The characteristic of the AC coefficients is sufficiently discussed, and based on the HVS, different inserting parameter is chosen for different block in embedding process. To shown the effectiveness of the proposed algorithm, several simulations are presented. In order to test the imperceptibility and robustness of the three algorithms mentioned above, a lot of experiments are done. Experimental results demonstrate that our schemes are effective and useful. Because of the simpleness and convenience, they may be expected to have a wide application prospect.