Research Of Watermark-based Digital Image Content Authentication

This paper mainly study image authentication algorithm based on watermark.According to the anti-attack strength of watermark information, the imageauthentication algorithm can be divided into fragile watermarking and semi-fragilewatermarking. The fragile watermarking algorithm does not allow the watermark tosuffer any form of signal processing or modify operations. The algorithm is applied toprotect the integrity of the image, such as medical images and the court photos. Thewatermark information of semi-fragile watermarking algorithm will not change aftersuffering a normal image processing operations, but it very sensitive to the operationof modify the image content information. This paper regards image as the mainresearch object and revolves around the basic theory of digital watermark to do somedeeply study about image content authentication based on watermarking technology.The main work of this paper includes:(1) A fragile watermark algorithm based on chaotic map is proposed. Fragilewatermarking is applied to image content authenticity and integrity of authentication.Base on hierarchical technology sustaining the superior location accuracy andeffective thwarting VQ attacks idea, a more secure and effectively resist the constantvalue attacks algorithm is proposed. Firstly, the image is divided into blocks and thenthe algorithm uses the skew tent map to generate a random number as a key togenerate the authentication watermarking, the average value of high six bits of theblock as the recovery watermarking. Finally embedding block location calculationusing the ultra chaotic sequence generated that enhance the security of algorithm.Experimental results show that the algorithm has good tamper localization, repaircapability and a higher security which can effectively resist VQ attack and constantvalue attack.(2) Based on the characteristics that the image entropy computing process hasnothing to do with specific colors and position of the image, the paper points out somedefects for using the image entropy as the image characteristics of the image hashingalgorithm which applied to content-based image authentication. Combined withspecific experimental analysis the paper presents three effective attack plans: Locationattack, Color attack and Pixel adjusting attack. Experimental results show that even though the image is not the same on the vision, through the pixel adjustment attack,itcan also through the system certification. Finally, this paper presents using imageentropy as a hash sequence for image authentication is not secure enough andintroduces several improvements.The proposed algorithm in this paper can be used for content authenticity,integrity authentication applications. Experiments show the advantages of proposedalgorithm compared with similar algorithms.