Digital Watermarking for

In this paper, we consider the problem of digital watermarking to ensure the credibility of multimedia. We speci cally address the problem of fragile digital watermarking for the tamper-proo ng of still images. Applications of our problem include authentication for courtroom evidence, insurance claims and journalistic photography. We present a novel fragile watermarking approach which embeds a watermark in the discrete wavelet domain of the image by quantizing the corresponding coe cients. Tamper detection is possible in localized spatial and frequency regions. Unlike previously proposed techniques, this novel approach provides information on speci c frequencies of the image that have been modi ed. This allows the user to make application-dependent decisions concerning whether an image, which is JPEG compressed for instance, still has credibility. Analysis is provided to evaluate the performance of the technique to varying system parameters. In addition, we compare the performance of the proposed method to existing fragile watermarking techniques to demonstrate the success and potential of the method for practical multimedia tamper-proo ng and authentication.