| Summary: | 碩士 === 國防大學中正理工學院 === 電子工程研究所 === 90 === As the development of World Wide Web, the data distribution is becoming faster, and requiring less effort to make copies. One of the major challenges is that of discouraging unauthorized copying and distributing electronic documents. Digital watermarking is seen as a viable solution to authentication of multimedia data in a networked environment.
In the pass decades, the study in digital watermarking has been presented as a solution to the copyright protection. Because of the development of this technique, private data can be transmitted by network to the full and achieve its concealment. In this thesis, a novel robust watermark technique is proposed to prevent the copyright of electronic document or image file been attacked from pirates in the network transmission.
The aim of the proposed method is to resist cropping attack. First, the original image is segmented into four sub-images, and then makes them chaotic to change relative position with each pixel. Second, a binary logo is selected to act as the digital watermark and then make it to chaotic watermark. The embedding process is based on Discrete Cosine Transform (DCT) to embed the chaotic watermark into the original sub-image individual in the transform domain. The experimental results shown that the proposed watermarking scheme is robust to against cropping attack and JPEG compression.
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