Abstract: Digital image manipulation software is now readily available on personal computers. It is therefore very simple to tamper with any image and make it available to others. Insuring digital image integrity becomes a major issue. In this paper, a new semi-fragile watermarking algorithm, claaed HSFW, is presented. Using a hierarchical structure and the idea of multi-resolution, HSFW can avoid the vector quantization (VQ) counterfeiting attack and identify the positions of corrupted blocks under different resolutions without the source image. By the reconstruction of DCT coefficient, HSFW can accept JPEG lossy compression on the watermarked image to a pre-determined quality factor, and reject malicious attacks. The experimental results show its effectiveness in protecting the content-integrity of images.

Key words: authentication, semi-fragile watermark, tamper localization, multi-resolution