Self-embedding Digital Watermark Algorithm For Image Authentication

With the rapidly development of computer network technology, the emergence of digital multimedia has greatly enriched the ways of access to information for people, it also conveniently accessed and conveyed for the information. However, the multimedia information would be subjected to all kinds of intentional or unintentional tampering attacks during transmission. How to authenticate the facility and integrity of the multimedia content is an urgent problem to resolve, which has become one of the hot issues of today’s information security fields. Image authentication is proposed to solve the above problems, and it has been rapidly developed in recent years. Its purpose is to detect and identify the facility and integrity of the image content, through the tamper localization and tamper recovery to apply tamper evidence. It effectively guarantees the security of digital image storage and transmission.This article makes a series of study for image authentication technology, discusses the background and significance of authentication watermark, and the theory of digital watermarking technology for image authentication. Highlights the existing fragile watermarking and semi-fragile watermarking algorithm, analysis and compares their advantages and disadvantages, and proposed three improved image authentication schemes based on this.To against JPEG compression, a semi-fragile watermarking algorithm is proposed based on hadamard transforms. Firstly the image is divided into8X8blocks, extracting the characteristics of image content to generate authentication watermark. Then the authentication watermark is encrypted by chaotic, and embedded in each hadamard main energy component. Finally, comparing the extracted watermark with re-extracted image content features to achieve the image authentication. It can detect and localization the tampering. Experimental results show the algorithm not only has better tamper detection and capabilities, but also has good resistance to JPEG compression attacks.The existing fragile watermarking algorithms almost can not recognize the modification is made on the image content or on the embedded watermark. A self-embedding fragile watermarking algorithm is proposed based on discrete wavelet transform. The high6bits of original image is transformed by discrete wavelet transform. Then recovery watermark is obtained form low-frequency of quantized and chaotic scrambling, and embedded it into the Hypo-LSB of image. Meanwhile the blocks of embedded recovery watermark generate the authentication watermark, and embedded it into LSB bits of image blocks self. Experiments result shows that the proposed algorithm not only locates tampered blocks accurately, but also discriminating the modification is made on the image content or on the embedded watermark, it also can restore tampered content region, and the quality of recovery is effectively.Based on hadamard domain, an image algorithm of self-embedded and self-recovery is presented. Firstly the image is divided into small8X8blocks and each block is hadamard transformed. Then the main coefficient after quantization, coding and encryption embedded into the lowest two sub-blocks offset being. According to a large number of image based on the statistical properties of hadamard transform coefficients, coefficient coding table is designed to make it better meet the quality requirements of the image recover. Experimental results show that the algorithm not only detect accurate positioning, but also it can restore the tampered region is effective.