Research On Digital Watermarking Techniques

The digital media has become a main way for information communication along with the wide use of network. At the same time, multimedia information security problems emerged as side effects of the popularity of digital representation and distribution over network. So the protection and enforcement of intellectual property for digital media has become an important issue. Watermarking which is one of the important fields of information hiding and the effective means to protect copyrights piracy is receiving increasing attention. It is the direct embedding of additional information into multimedia signal. Ideally, there should be no perceptible difference between the watermarked and original signal, and the watermark should be difficult to remove or alter without damaging the host signal. In this paper, we limit the scope of our research to robust and imperceptible digital watermarking. The main contributions of this dissertation are:In order to improve watermarking robustness against distortions and attacks, it is natural to envision the use of error correcting codes. According to the principle of RS, we encrypt the watermark which is an image. By limiting a different level to error permit, there is more difficulty in gaining the watermark when the destroyer doesn't know the level and the data quantity. As for the embedded ways, we introduce the common way of embedding the watermark to the special domain of the image.A watermarked image encryption bases on chaos sequence. Chaotic sequences have several good properties including the ease of their generation, the sensitive dependence on their initial condition and the statistics property of noise. We implement the image encryption algorithm based on the technique of image scrambling transformation in special and frequency domain. And more, we embed the watermark to the special and frequency domain of the digital product. Preliminary results are satisfactory and efficient.Watermark is some information produced by the nonlinear function. That is to say, we encrypt the important information by repeating to use the nonlinear function.As a result, the watermark may be a sequence. The important information may be abstracted out of the watermark only in several sequence data. At the same time, we deal with the product to some block according to the human vision system and embed the watermark to blocks.