Secure and robust watermarking technique

Digital image-watermarking can be casted as an optimization problem with solution satisfying fidelity, robustness and security constraints. Most of discrete wavelet transform (DWT) and singular value decomposition (SVD) based approaches highlights tradeoff between fidelity and robustness with lesser discussion on security. In this paper, authors propose a novel watermarking approach based on DWT and SVD to satisfy all the three constraints. In this approach watermark is customized using singular values (SV) computed on DWT sub-band of cover image. Unlike other algorithms, watermark is not inserted into SV´s of DWT sub-band. While doing singular value decomposition on cover image, SV´s of watermark replaces the SV´s of the DWT sub-band. Signatures of orthogonal matrices associated with SV´s of watermark are then computed and inserted into third level LL and HH band of cover image. Before watermark extraction these signatures can be used for authentication of the orthogonal matrices. Signature authentication improves security of the algorithm. Experimental results are provided to show that new watermarking method performs well under all three constraints.