A Multipurpose Watermarking Scheme for Image Authentication and Copyright Protection

In this paper, we present a novel multipurpose digital image watermarking scheme based on discrete wavelet transform (DWT) and chaotic map, which can be applied to image authentication and copyright protection. In the proposed scheme, by performing 2-level DWT of the host image, the robust watermarks are embedded in the low frequency sub-band LL2 of the host image, and the semi-fragile watermarks, generated by chaotic map, are embedded in the high frequency sub-bands HL2, LH2 or HH2, and the embedding coefficients are selected randomly by secret key. A improved quantization method (IQM) is utilized to embed robust watermarks. Watermarks can be extracted without the original image. Simulation results demonstrate the effectiveness of our algorithm in terms of robustness and fragility.