Research And Implementation Of Seal Domain Digital Watermarking Security System

This thesis aims to research on the seal domain watermarking algorithm, which can resist the geometric attack and Print-Scan procedure. The combination of digital watermarking and digital signature makes fully functional copy of the traditional approach. Seal domain watermarking security system is based on PKI/CA platform. With the technology of seal domain watermarking, this system manages to protect both digital documents and physical documents. The system expands the application fields of digital watermarking and PKI from the digital domain to the analog domain. Main contributions of this thesis may include:1. There are many difficulties in the design of seal domain watermarking algorithm. We have applied a seal domain watermarking algorithm that is based on standard deviation in the real project. According to the problems we have encountered, this paper presents the corresponding solutions. To solve the registration problem of scanning images, we propose a registration algorithm, which is based on DFT and variable sampling-rate Polar transform. The watermark decision threshold is lack of adaptability to the illumination and the print quality. So we propose a method to normalize the watermark decision threshold, which greatly improves the success rate of watermark judgment.2. Due to the characteristics of the seal images, it is not easy for the watermarking algorithm to fulfill the requirements of both transparency and robustness. This paper presents a novel watermarking algorithm, which is based on Discrete cosine transform and Stochastic Resonance theory Stochastic Resonance theory and discrete cosine transform. The proposed watermarking scheme is robust against common watermark attacks, and the watermark embedded is almost transparent.3. Adhere to the object-oriented design methods, designed and implemented a seal-domain digital watermarking subsystem, which have good performance on scalability and reusability.