An Improved Semi-fragile Digital Watermarking Scheme for Image Authentication

This paper proposes an improved semi-fragile digital watermarking scheme for image authentication based on the technique proposed in. In the new scheme, the watermark is not user-defined, but generated by a quantization function in the discrete wavelet domain of the image. We embed watermarks by quantizing the corresponding wavelet coefficients. The watermarked image is lossless since no distortion is introduced into the original image. With this technique, we can embed watermark even without implementing inverse DWT, and then numerical sensitivity discussed in is no longer a headache. In addition, multiple watermarks can be simultaneously embedded into same image by defining various quantization parameters to provide more information for image authentication.