Digital watermarks offer a way to counter copyright piracy on the global network. We summarize the fundamental concepts of watermarking and describe a general framework for a copyright protection system. Watermarks efficiently protect copyright when basic demands can be satisfied. However, the demand for watermarks to remain robust under digital image-processing operations has not yet been fully satisfied. Robustness to geometrical distortions is an essential remaining problem for schemes that do not use the original images in the detection procedure. Furthermore, new watermarking schemes must take into account optimizations of current processing algorithms and the development of new algorithms. Better future compression techniques, for example, must not destroy watermarks embedded at any earlier time.
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