Digital Watermarking: Algorithm Implementation And System Analysis

The rapid growth of digital imagery, the increasingly easy access to digital media, and the increasingly powerful tools available for manipulating digital media have made media security a very important issue. The digital watermarking technique has been proposed as a promising means for intellectual property protection of multimedia data and has been a hot topic in both the academic world and the business society all the time.In this thesis, we first point out its application areas, requirements, system framework and relationship with other disciplines. Then we categorize the algorithms in the literature, introduce some classical ones and analyze the research progress. We also discuss the embedding capacity, the optimum watermark decoder and detector and system protocol.In the third chapter, we first detail some watermarking attacks including watermark removal attacks, cryptographic attacks and protocol attacks. The desynchronization attack is very difficult to tackle and still an open question. We then highlight it and summarize the countermeasures.In the fourth chapter, we propose an image content-based high capacity algorithm. Embedding is selectively done in 8 X 8 blocks whose standard variance is less than the average of 8-neighbor connective blocks', and strength factor is determined by local image contents. Watermark's detection doesn't need the original unwatermarked image and thus it is a blind scheme. Simulation results demonstrate its robustness and high watermarking capacity simultaneously.Finally, some concluding remarks are made and my research experience since one year ago is retrospected. We also expatiate on the bottleneck digital watermarking is confronted with. In conclusion, we hold a prudential and wait-and-see opinion about it and suggest that we should not devote too much time to it any longer.