基于数字水印的图像认证技术

伴随着数字水印技术的发展，用来解决数字图像的真实性问题的图像认证技术在近年来发展迅速．它主要包括两大部分：篡改检测与篡改定位．有两种技术手段可供它使用：数字签名和数字水印．该文详细讨论了在设计基于数字水印的图像认证算法时常见的若干关键问题，阐述了基于数字水印的精确认证和模糊认证算法各自的发展过程及其国内外现状，并指出了将来继续努力的方向．

Image Authentication Based on Digital Watermarking

With the development of digital watermarking technology, image authentication technology, which can be used to verify the integrity of a digital image, has been under active study in recent years. It mainly contains two parts: tamper detection and tamper localization, where the former aims at verifying the integrity of an image, while the latter is dedicated to localize maliciously tampered pixels if any. Both digital signature and digital watermarking can be utilized by image authentication. This paper focuses on image authentication based on digital watermarking technology. Several general key problems when designing such an algorithm are discussed first, including the allowable manipulations, the feature extraction, the precision of tamper localization, the restorableness of tampering, the influence of watermark embedding and the security of the system. Then, the literature and the state of the art of two classes of watermarking based image authentication algorithms (exact authentication and selective authentication) are introduced, respectively. As for exact authentication, there is no scheme which is secure enough and can localize the tampering to a single-pixel level up to now. The most important problem is to make a good tradeoff between the fine tamper localization and the system security. As to selective authentication, there are no satisfying schemes in the literature. The future direction is pointed out finally. The goal of exact authentication is to achieve finer tamper localization when keeping enough security, while the urgent affairs of selective authentication are to extract one kind of image feature which can describe the content of an image adequately.