| Summary: | 碩士 === 國立交通大學 === 資訊科學系 === 91 === Because of the proliferation of digital images on the Internet, people can carry and transmit information by digital images conveniently. For this purpose, some methods for covert communication are proposed in this study. Besides, with the advances of digital techniques, digital images may be copied or tampered with illegally. To solve such problems, some methods for copyright protection and tampering detection for various types of images are proposed in this study. For grayscale images, a method based on visible watermarking techniques and a human visual model is proposed to protect copyrights and detect image alterations. For binary images, a data hiding method is proposed to embed up to two bits in a 3´3 image block by changing at most just one bit in a block. An authentication method for verifying the fidelity and integrity of binary images is also proposed, which creates authentication signals by rearranging the pixels in image blocks. Three methods integrating various data hiding techniques to embed invisible watermarks, visible watermarks, annotations, and authentication signals into three types of images are finally proposed. Good experimental results prove the feasibility of the proposed methods. Finally, some mechanisms for multiple authorizations of images are proposed and some functions of an image authentication center are also suggested.
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