Research On Transform Domain Watermarking Technique For Image Authentication

With the rapid development and application of the network technology and multimedia technologies, more and more digital images have been spread conveniently on the network, but they are easy to get tampered maliciously during the spreading process, and cause adverse consequences. Therefore, how to protect the authenticity and integrity of image has become an urgent problem to solve. As an important means to protect digital image, image authentication watermarking technology which is used to determine the image authenticity and integrity problem, has become a hotspot of current research.This article is based on some relevant basic theories about digital watermarking for image authentication, and has carried on in-depth analysis and discussion to the existing image authentication watermarking algorithm. In view of the problems such as the existing image authentication watermarking algorithm shortcomings, and considering the digital image requires compact storage and transmission in the practical application, in addition that the user is only concerned about the image content information to be expressed, this article proposes a semi-fragile digital watermarking algorithm for image content authentication. The main works of this article includes:(1) Proposing a semi-fragile digital watermarking algorithm. The algorithm can be used to verify the authenticity and integrity of image content. Firstly, the algorithm extracts the edge of the scaled image as the feature information, and the feature information is chaotically modulated and ciphered with the private key in order to generate the watermark information. Secondly, the watermark information is embedded into the wavelet domain of the host image by using the technique based on human visual system. Finally, a user can extract the feature information from the watermarked image with the public key, and compare the extracted feature information with the reconstructed feature information of the watermarked image to achieve authentication.(2) Improving RST immunity of the watermarking algorithm. In order to have RST invariability, the parameters of geometric distortions are estimated and restored before extracting the watermark by using the original moment information.We also experimented with the proposed watermarking algorithm. The experiment results show that the watermarking algorithm not only attains the transparency, security and practicability, but also has the immunity to common image operation, and achieve accurate authentication and tampering localization to malicious processing. Therefore, the proposed watermarking algorithm has a theoretical and practical value.