A robust watermark algorithm based on wavelet

In this paper, we proposed a strong watermark algorithm for digital image protection based on wavelet. Instead of adding watermark into source image, we use it to generate a standard key to identify the copyright and ownership. The key will be sent to a third party, and there will be no modification to the source, which means this algorithm guarantees perceptual invisibility. We use a 256-level image as watermark and convert every pixel into an 8-bit binary; it has been proven that both stability and amount of embedded information were increased. Besides, taking full advantage of average compare is doubly enhanced the strength. We will illustrate its effectiveness and robustness by showing the detecting result after experimental attacks.