Study On Lossless Digital Watermarking For Image Authentication

Watermarking is the process that embeds data called watermark into a multimedia object, such as image, video, or text, for some purpose. There are two types of watermark, fragile watermark and robust watermark. A fragile watermark is a mark which is highly sensitive to modification. A fragile watermarking scheme should be able to detect any change in the signal and identify where it has taken place , some schemes can recover the original signal.With the rapid growth of Internet usage, digital multimedia works becomes more and more easy to be acquired, copied and transmitted. Consequently, the protection of integrity of these works turns to be an important issue. There are a special multimedia such as medical images and legal litigation images, any alteration of this sort of images is prohibited, because the alteration possibly bring the change of diagnosis result or the argument of legal evidence. The protection of integrity can be acquired through inserting watermark into these images, but after the watermark was extracted, the original image needed to be recover properly. Furthermore, it needed to identify where the change has taken place. Lossless watermarking is one of the methods to solve the issue.This paper focuses on the research of the lossless watermarking. There are four aspects. Firstly, the basic conception and realization principle of the lossless watermarking is analysed through studying correlative papers; Secondly, the lossless watermarking is used for image authentication,which consists of lossless data embedding and data authentication.The paper study a algorithm for lossless data embedding named DE, then simplify the algorithm and implement the former algorithm and the simplified algorithm. It had been proved than the simplified algorithm decrease computation complexity and increase the fidelity of watermarked images; Thirdly,a new lossless watermarking scheme based on the simplified DE algorithm is put forward and implemented.Differ from existent schemes,the new scheme can authenticate the image before the image was restored,thus decreaseing computation complexity. Fourthly,most of the lossless watermarking can provide authentication but can't provide function of tamper localization. A localized lossless authentication watermarking based on existing result is introduced and realized. Furthermore , a public key scheme and private key scheme is implemented.