Digital Watermarking Algorithm Based On Block Discrete Wavelet Transform

In recent years,with the rapid development of network security technology and information hiding technology,the digital watermarking technology,as a new one,has been wildly used in copyright protection,information sources authentication,information integrity verification and so on.Different fom encryption technology,digital watermarking technology embeds some secret information into the original documental information of the multimedia through a cereain algorithm,without affecting the contents and values of the original multimedia file,and meantime it's not easy to be perceived by naked eyes.Whether a watermarking algorithm is excellent or not is decided directly by its performance to resist various common attacks.Therefore,the algorithm must ensure the imperceptibility,robustness and security of the digital watermarking.This thesis mainly studies a block-embedded watermarking algorithm based on DWT technique,and proposes two schemes to improve the existent algorithm utilizing the characteristics of block-based embedded technology.The following work has been accomplished.1.Spatial domain algorithm is analyzed and revealed its inadequacy.Damage in compression may result in complete loss of the watermarking even by a tiny change.Moreover,resistance to JPEG lossy compression attack and cut attack is found to be insufficient,and the robustness of the technique remains to be improved.2.A block-embedded watermarking algorithm based on DWT is proposed.This algorithm initiates the scrambling transformation of the watermarking data,and proceeds to process the carrier image in blocks,which is then embedded with watermarking.The robustness of digital watermarking is thus improved through disseminating watermarking data in blocks.3.A color digital image watermarking algorithm based on DWT is proposed.Color digital image can be decomposed into tri-color R,G and B,which can be further processed by wavelet decomposition.Next,embed scrambled watermarking image into the transformed tri-color,employ IDWT technique to integrate die tri-color components,and finally harvest the desired watermarking color image.Results suggest the improved digital watermarking algorithm can resist common attacks with more robustness.