Image Authentication Technology Based On Digital Watermarking

Along with the fast development of the multi-media technology and computer network, more and more digital products are being transmitted through the internet. While bringing great convenience to people's life, it also causes illegal copy and malicious tempering. Under this circumstance, the digital watermarking technology is being widely applied to protect multi-media products, especially used as a solution for digital image authentication.In order to judge the accuracy and integrity of the images, authentication techniques have been developed accordingly. Image authentication technologies fall into two categories, which are signature-based image authentication and watermark-based image authentication. Signature-based image authentication technologies require additional signature information, on the contrary, watermark-based image authentication technologies embed watermark in the original image with no need of additional information. Therefore, watermark-based method is generally common used in image authentication area.1)Discussed the basic concept of digital watermarking, theories foundation, main application and summarized the research contents, key issues, general model that integrated authentication of image.2)A New Algorithm of 2-Dimension Color Image Digital Watermarking is proposed. Considering the characteristic of Human Visual System (HVS), proposed method in this paper adopts YIQ color space, and embeds a grayscale image into the luminance Y of the color image by using discrete cosine transform, and increases the bit embedding quantity in more complex blocks. In addition, through Arnold transform, the watermarking image is hashed to eliminate the spatial correlation among pixels, which enhances the algorithm's anti-attack ability. The experimental results show that the proposed watermarking scheme is robust for various attacks such as noise adding, JPEG compression, cropping, and image enhancement.3 ) An image authentication algorithm which can robust against JPEG compression is proposed. The feature code is based on the invariance of the relationships between discrete cosine transform (DCT) coefficients at the same position in the separate blocks of an image. The feature code which has been encrypted is embedded in the original image as a watermark. In authentication process, the feature code of receiving image would be compared with the decrypted watermark draw out from the image. Using tamper matrix to distinguish whether the content has been tampered, then show the specific tampered location. Experimental results show that this algorithm has a good performance to robust against JPEG compression, and can effectively detect the event and the tamper location when the content of the original image was tampered.