Research Of Digital Image Watermarking And Authentication Technique

This paper aims to implement image copyright protection and authentication. Firstly, this paper introduces the basic model frame of image digital watermark. This paper analyzes current processing technology for image digital watermark, which includes creation,embedment,extraction,detection and authentication. We summarize current research status quoin this field. Then we narrate signal wavelet processing and image processing in wavelet domain. After we explain EmbeddedZerotree Wavelet (EZW) coding, we take Human Visual System (HVS) and Watermark Assault Model into account and put forward a new watermark algorithm for static grew image, through which we can implement watermark embedment and detection. At last we propose a half frangible watermark algorithm based on the theory of digital signature, which can authenticate the integrity of image.We have mainly completed the following work in this paper:1. We analyze the theory and progress of wavelet transform and dispose image watermark through Discrete Wavelet Transform (DWT), at the same time many scholars have been doing this through Discrete Cosine Transform(DCT). DWT has three main advantages over DCT guaranteeing that image watermark won't be eliminated if the original image is compressed; wavelet has the peculiarity of visual multiresolution which is consistent with HVS, so we can choose appropriate position and intensity to embed watermark information; we can embed watermark in image compressing domain.2. We embark on thorough research for EZW technique and advance a watermark algorithm based on important coefficients of wavelet tree. In this paper we suggest that we should choose important coefficients with intermediate frequency or low frequency firstly, then embed watermark information in each kind of Coefficients thus watermark will have good robustness and image quality.3. We reference the theory of digital signature to bring forward a half fragile watermark algorithm based on image content which can be used for authenticating the integrity of image.