Digital Blind Watermarking Algorithm Research Based On Copyright Authentication

With the development of information technology, the digital works has become parts of EDI (Electronic Data Interchange). How to authenticate and protect the copyrights of the digital works has become one of the studies of the multimedia information security, among which digital watermarking technique is one of the hottest issues. Compared with traditional cipher technique, the digital watermarking needs no additional authentications and is embedded in the works themselves. It cannot be felt and can be allowed to lack fidelity to some degree. As a result, watermarking technique has become a new technique to counter forge digital works. It provides a vast application spaces for digital works, such as image works, audio works, visual works, etc. Nowadays, there are two watermarking algorithms used for copyright authentication: one is robustness, the other is fragility. The robustness watermarking has a much wider application in digital copyright authentication.This dissertation deals with some researches on copyright authentications and techniques of image and digital watermarking. The research achievements are as follow:Advance an algorithm of selecting and grouping watermarking based on DCT frequency domain. Traditional image and digital watermarking algorithm on DCT frequency domain is that watermarkings are selected independently and listed at random within gauss normal distribution N(0,l). With strong robustness and insufficient inlaid watermarking, such algorithm is unfit to embed grey or color watermarking with larger resolution on image. In order to solve this problem, a method of optimizing preprocess is used in this dissertation, e.g. classify and select the sub-block coefficient in DCT domain by HVS frequency; lower the quantization effect in DCT block by JND threshold of gray-image, embed in the owner image after compressing and disordering 256 level grey watermarking image. The experimental result shows that this kind of watermarking has a good covert effect. It has an effective ability to counter compression and noise.Advance an algorithm based on spreading spectrum communities on DCT domain. By transferring watermarking image and mapping gray image into a set of bipolar, a watermarking signal can be made as its pseudo-random sequence and then by means of spreading spectrum embedded this kind of watermarking into frequency domain sub-block selected by the coded keys. This algorithm comes up with a solution to embed watermarkings at random. It has a strong effect on resisting JPEG compression and noise and the watermarking has a good function of concealment and robustness.Advance an algorithm of embedding multiple digital blind watermarking based on DCT frequency domain and its check or extraction. The frequency domain of the owner image is transferred into the substitution of DCT of 2-D by the technique of spreading spectrum communications. Select and group the frequency domain of the owner image by JND threshold of gray-image and the multiple-based work underlying, embedded watermark bit by group to AC of intermediate frequency, control the embedded watermark bit according to AC of high-low frequency at random, and thus the carrier wave of the signals of multiple digital blind watermarking can be transferred into the multiple-layered DCT frequency domain. This algorithm can forecast the amount of the embedding watermark. To get the watermarking, there is no need to use owner image or watermarking image. The experiment results shows that this algorithm can effectively resist filtering waves, added noises, clipping and JPEG compression. It has a greater characteristic of robustness and renitence.