Watermarking Techniques For Multimedia Authentication And Copyright Protection

The revolution in digital technology has increased the ease of manipulation, reproduction, retransmission, and distribution of digital information. However, it is also offers the potential for illegal duplication and manipulation. Consequently, management and protection of these digital properties have become crucial. Digital watermarking technology is considered as an alternative tool for protecting these intellectual properties. It attempts to embed copyright and authentication codes within media content to identify the true owner and authenticate the digital information.Digital watermarking was first proposed in the early 1990s as a solution to prevent the unauthorized duplication and distribution of copyrighted multimedia data. And since then, it has attracted attention more and more. Now, digital watermarking has many other applications such as data authentication, indexing data, data hiding, and so on. Most research efforts are poured into the areas related to copyright protection and data authentication. Supported by Hong Kong City University, this dissertation mainly focuses digital watermarking for data authentication and copyright protection. Some new algorithms are presented and tested and some problems in both theory and practical applications are solved successfully. The major achievements of this dissertation are outlined as follows.For data authentication, we propose a wavelet based fragile watermarking algorithm, which takes full advantage of characters of a wavelet, limits the minimum distance between the value of coefficients and quantization boundary, and uses our method to round image pixels to integer values to form a digital image. The experiments show that compared with other recently proposed algorithms, our algorithm has following advantages: (1) high security; (2) high robustness; (3) good watermark detection capability; and (4) capability to detect changes of images in localized spatial and frequency regions.For image copyright protection, we propose a novel hybrid watermarking algorithm by thorough analysis of two classes of watermark embedding methods: one based on spread spectrum technique and the other one based on quantization technique. Experiments show that our algorithm is more robust than the well-known spread spectrum blind watermarking algorithm.To protect digital video copyright, we propose a robust real-time video watermarking algorithm which embeds watermarks in compressed bit stream. It takes full advantage of masking sensitivities of the human visual system (HVS) and uses watermark break technique to improve the robustness of the embedded watermarks. Experiment results are reported proving therobustness of the proposed algorithm against some of the most common video processing techniques.For 3D model copyright protection, we propose a robust watermarking algorithm for 3D models which embeds watermark information by perturbing the distance between the vertices of the model to the centre of the model. To improve the robustness of the algorithm, we propose a new method to control the local watermarking strength and develop a weighting process of watermark detection. Compared with other well-known 3D model watermarking algorithm, our algorithm has following advantages: (1) it is able distribute information corresponds to a bit of the watermark over the entire model; (2) its method to control the local watermarking strength is more better than other ones; and (3) its weighting process of the watermark detection improves its robustness against a variety of attacks.