A Water Marking Algorithm of Digital Image Based on DWT-SVD

This paper presented a water marking algorithm based on discrete wavelet transform (DWT) of image and singular value decomposition (SVD). After decomposing the original image into four bands, the SVD is applied to the blocks of the low sub-band. To improve the security the watermark is scrambled by Arnold transform, and then is embedded into the largest singular value of every block. The watermark can be extracted without the original image, among which a person who does not know the secret key cannot correctly retrieve the watermark.