| Summary: | 碩士 === 國立臺中技術學院 === 資訊科技與應用研究所 === 95 === This thesis focuses on digital watermarking and its applications in database protection. Digital watermarking is a kind of information hiding techniques, it can partition into two parts: one is robust watermarking for copyright protection, the other is fragile watermarking for tampering detection. Database watermarking is used to protect the database by embedding digital watermarks into the protected database. Hence digital watermarking can be used to achieve database ownership verification and tampering detection. In recent years, most existing database watermarking schemes altered the data of tables to embed watermarks. However, most data in a database are sensitive. When some data are modified, it would let the data become useless. Hence, how to embed watermark without modifying any data is very important. In this thesis, a database watermarking schemes is proposed that it embed watermark into databases without destroying any protected data’s meaning. This scheme extracts a feature from each tuple to combine with each pixel of a watermark image for embedding a robust watermark, and the features of each couple of t uples are compared to embed a fragile watermark by an embedding rule. The experimental results showed that the proposed scheme can not only copyright verification but also tampering detection, and have a significant achievement.
In addition, this thesis proposed two reversible watermarking schemes to protect database. These schemes can restore original data after extracting watermark and verify ownership or integrity according to extracting watermark. The first scheme is a robust reversible watermarking scheme by building quart-tree to embed a watermark. The first reversible watermarking scheme utilizes extracting features from every attributes to build quarter-tree. When user verified ownership according to the extracted watermark, the data in the database can restore its original value. The experimental results showed that the first reversible watermarking scheme can not only achieve copyright verification by extracting watermark under different alteration rate attacks and attribute out-of-order attacks but also restore original data after extracting watermark image. The second scheme is a fragile reversible watermarking by using de-clustering technique to embed a watermark. The second reversible watermarking scheme utilizes extracting features from every attribute to group four groups for representing watermark information. It utilizes features of every attributes to find the small least value from the corresponding watermark group and utilizes the fined value to change the original feature of the attribute for embedding watermark. When users verified database integrity according to the extracted watermark, the data can restore the original value in the same time. The experimental results showed that the second reversible watermarking scheme not only verifies integrity of database but also restores original data in 100% rate after extracting watermark.
Keywords: Digital watermarking, copyright protection, database watermarking, dual watermarking, ownership verification, integrity verification, reversible watermarking, de-clustering technique.
|
|---|
