Research On Digital Watermarking Algorithms Against Geometric Attacks

With the rapid development of Internet and computer science technology,more and more digital information is susceptible to malicious copying and tampering by illegal users,which has caused widespread concern in the field of multimedia copyright protection and digital information security.Copyright protection and image authentication can be achieved by digital watermark technology,which has become a research hotspot in the international academic community.At present,the research of digital watermarking technology has made great progress,but the digital watermarking algorithm for geometric attacks is still a research difficulty in the field of multimedia information security.This paper studies digital watermarking technology,firstly it introduces the basic concepts and classification of digital watermarking,then summarizes the various digital watermarking attack methods and evaluation criteria,and then proposes the corresponding digital watermarking algorithm against resistant to geometric attacks.(1)A zero watermarking algorithm based on improved Sobel operator is proposed.The algorithm firstly divides the original image into non-overlapping blocks and averages them,and then recombines to form an approximate image.Secondly,the improved Sobel operator is used to extract the image edge information features,and the feature vectors are obtained through polar coordinate transformation and other processing;Then,the doubly encrypted watermark information by Fibonacci transform and Logistic chaotic mapping XOR the feature vectors to obtain a zero watermark.Finally,the zero watermark is registered with the certification center.The experimental results show that the constructed zero watermark can not only resist the conventional image processing attacks such as noise,filtering and JPEG compression,but also has strong robustness against geometric attacks such as scaling,cropping and rotation.(2)Based on the above research,a zero watermarking algorithm based on non-negative matrix factorization(NMF)against strong shear attacks is proposed.The algorithm first decomposes the original image through NMF,and registers the obtained coefficient matrix in the copyright center as part of an zero watermark information.Using the global characteristics of NMF local perception,a complete base matrix can be recovered from a complete sub-block after being subjected to a shear attack,and then the original image is reconstructed to extract a complete and accurate watermark.Compared with the existing watermarking technology,the algorithm can effectively resist strong cropping attacks and has strong robustness against various other image processing attacks(such as scaling,filtering,noise,compression).