| Summary: | 碩士 === 國立高雄應用科技大學 === 資訊工程系 === 99 === Recently, digital information hiding technique has been used widely in identification of authenticity and authentication of intellectual property rights, and image is focus on developing digital watermarking. Conventionally, single digital watermarking embedding is the main topic of image information hiding, and either visible or invisible watermarking technique is utilized. Information is embedded into spatial domain and frequency domain in using visible watermarking and invisible watermarking, respectively. Due to unpredicted attack, the performance of single digital watermarking protection is limited. Malicious attacking using geometric and signal processing worsen the information in single watermark embed. In this research, we propose a modified algorithm on dual digital watermarking, not only improve the performance on embedding and extracting, but also enhance the PSNR value after embedding. It provides the advantages of both visible and invisible watermarking simultaneously. Visual protection to avoid unauthorized use is achieved by visible watermarking and robustness and security are accomplished by invisible watermarking. When the authorized user want to remove the dual digital watermark for retrieving the original image, user just giving the right security key and variable values.
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