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“Improving the Security of Wavelet-based Watermarking Systems” by W. Dietl. Masters thesis, Salzburg University, Department of Scientific Computing, Dec. 2002.


Over the recent years research into copy protection schemes has seen widespread attention from both academia and content owners. The ease of content distribution over the Internet has allowed malicious users to quickly spread illegal copies of music, videos and images. Embedding invisible watermarks is used to prove the rightful owner of media and to deter illegitimate use. In this thesis we present two methods to improve the security of wavelet-based watermarking systems and analyze their properties in detail. In chapter 1 we give an introduction to watermarking, wavelet analysis and describe the watermarking algorithms we use. Chapter 2 introduces filter parametrization with between 2 and 20 parameters and uses non-stationary multi-resolution analysis to get a secure keyspace. The robustness to JPEG and JPEG2000 compression and the security against unauthorized detection is assessed. Chapter 3 describes how random wavelet packet decompositions can be used to increase the security. We describe two procedures to create random wavelet packet trees and three embedding variations and analyze the security and robustness of the proposed system. Finally, in chapter 4, we perform malicious attacks on the wavelet coefficients and try to remove the watermarks. We compare the behavior of the two proposed systems with the standard systems that use the pyramidal decomposition and either the Biorthogonal 7/9 or the Daubechies 6 filter. Both proposed systems show superior performance. We conclude the thesis with appendix A, example images, appendix B, a description of the development environment, the bibliography and a curriculum vitae.

The thesis won the Excellent Diploma Thesis Award from the Austrian Computer Society (OCG,

Keywords: watermarking security, wavelet, parametrized filters

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BibTeX entry:

   author = {W. Dietl},
   title = {{Improving the Security of Wavelet-based Watermarking Systems}},
   school = {Salzburg University, Department of Scientific Computing},
   month = dec,

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