数字水印外文.doc

A Digital Image Multiresolution Watermark Based on Human Visual System 1. Introduction The rapid development of Internet introduces a new set of challenging problems regarding security. One of the most significant problems is to prevent unauthorized copying of digital production from distribution. Digital watermarking has provided a powerful way to claim intellectual protection. Watermark must have two most important properties: transparency and robustness. Transparency refers to the perceptual quality of the watermarked data. The watermark should be invisible over all types. The digital watermark is still presented in the image after distortion and the watermark detector can detect it. Ideally, the amount of image distortion necessary to remove the watermark should degrade the desired image quality to the point of becoming commercially valueless. It is called the robustness of digital watermark to image processing. The common distortion of signal processing includes lossy compression (in particular JPEG), resampling, requantization, image enhancement, cropping, etc. A key point of the watermarking technique is the trade-off between the transparency and the robustness. We must determine where to insert watermark and how to enhance the robustness of the watermark. In this paper a wavelet based watermarking method using the HVS is presented. Lee adopted the RS code (Reed-Solomon code) to generate ECC code words, and regarded the codeword’s parities as watermark. They used watermark to recover the damaged image. But from the viewpoint of intellectual protection, the watermark is more important than the image, while the image quality is maintained. They did not handle the watermark. We proposed an idea for enhancing the robustness of extracted watermarks. Watermark can be treated as a transmitted signal, while the destruction from attackers is regarded as a noisy distortion in channel. According to the viewpoint mentioned above, we provide an idea using ECC to detect a