A Novel Blind and Fragile Digital Image Watermarking Technique Based on DWT-SVD

The trade-off between the imperceptibility and the strength of the embedded watermark is one of the most difficult challenges in digital watermarking systems. In certain applications, the watermark has to be preserved from any alterations within both the embedding and extracting processes, i.e. the strength of the watermark has to be maximized in such a manner that results in an identically extracted watermark. In this context, most of the existing methods suffer from one of the two shortcomings, represented by an enormous amount of alterations that may take place along with maximizing the strength of the embedded watermark, or the inability to give an identically extracted watermark. In light of these shortcomings, this thesis proposes a new fragile and blind watermarking technique for digital images, based on two-dimensional wavelet transformation domain and singular value decomposition. In addition to this, the effects of some watermarking techniques on watermarked images were investigated and compared against the proposed method in terms of the level of imperceptibility. The key idea of the proposed method is to hide the indices that would indicate the location of certain values of a watermark instead of hiding the watermark itself. For a binary watermark, the indices of the zero elements are selected. In this way, the imperceptibility level can be enhanced in a strongly embedded watermark. Through the experimental phase, the proposed method along with the other selected methods has undergone several simulation experiments in the grayscale domain to test and compare their levels of imperceptibility. After this, the proposed method has been compared with the best of the experimented methods in the colorful domain using the HSI color space. Keywords: Watermarking Image, Blind system, Watermark strength, DWT, SVD.