Research On Digital Watermarking For Relational Database

In the past decade, as the delivery and distribution of relational database by using computer networks has become easier, the difficulty of protecting database from illegal copies and reproduction has turned out to be more challenging. To address this concern and to fight against data piracy, digital watermarking is currently considered as the most convenient and promising technical solution.However, the digital watermark technology for database is so difficult that the progress of researches on it is being improved slowly. Specially, the database has large number of data but little redundancy and it needs some operations normally, so it can't adapt the traditional digital watermark technology on multimedia to watermarking database directly. We must find a new algorithm that satisfies the restriction on relational databases, based on analyzing the characteristics of relational database and digital watermarking. In this thesis, technology of digital watermarking was first introduced, and the restriction between relational databases and digital watermarking was studied. Popular attacks on watermarking relational databases were analyzed. The exceptional technology of watermarking on relational databases was summarized. To date, watermark technologies on relational databases face the following major challenges. Firstly, current watermark technologies only utilize spatial domain method, therefore more research work is needed to implement frequency domain concepts to enhance the watermark robustness. Secondly, relational data could be classified into numeric type and non-numeric type. However, current watermark technologies only deal with numeric data and seldom are achieved for non-numeric data. Therefore, the research of watermark technologies over non-numeric data will introduce a new hot topic and further popularize the applications of watermark technologies. To solve these two problems, the main works in this thesis were done as follows:first, using wavelets transform that is common way in watermarking media, we propose a method that uses wavelets transform to watermark on relational database. The process of embedding watermarking information into database makes the change of static characters, wavelets transform minimize this change. At the same time, this method ease computing load. Second, study particularity of inserting watermark into non-numeric data. Based on it, a model of watermarking on non-numeric relational data was proposed, and then improved. Experiments were designed to argue the usability of the algorithms, and the experimental results on several kinds of attacks were also given.