Analysis And Design Of Image Authentication System Based On Fragile Watermarking

With the development of science and technology,the transmission and sharing of digital images become faster and more efficient.It is especially important to identify the authenticity of the transmitted image.Image authentication technology has been proposed to solve this problem.Image authentication algorithms based on fragile watermarks have been widely studied by scholars.To enhance the security of fragile watermarking algorithms is the key to promote the development.The application of chaos theory to the field of fragile watermarking has become a research hotspot and promoted the development of fragile watermarking technology.This thesis first studies the security of fragile watermarking algorithms,and discovers that some algorithms only focus on the accuracy of tampering localization,but ignore the security.Then,analyze an image authentication algorithm based on fragile watermark.Finally,a more secure image authentication algorithm based on dual fragile watermarks is proposed.The research work of this thesis mainly includes the following two aspects:1)We analyzed the security of a self-embedding fragile watermark scheme proposed by Qin et al.The watermarking scheme is based on reference-bits interleaving and adaptive selection of embedding mode.We use a collage attack and a multiple stego-image attack to break this scheme respectively.This scheme has a feature of block independence of embedding watermark such that it is vulnerable to a collage attack.In addition,because the generation of authentication bits via hash function operations is not related to secret keys,an attacker can apply a multiple stego-image attack on this scheme and the cost of acquiring all the permutation relations is dependent on the clock size and embedding mode.The simulation results and the statistical results verify our analysis is effective.2)This thesis proposed a secure image authentication scheme based on dual fragile watermark,which meets the needs of both high security and accurate tamper localization.Combining the characteristics of image encryption and fragile watermarking,we designed a dual fragile watermark based on chaos theory.Two fragile watermarks called as diffusion and authentication watermarks are embedded into the cover image.Diffusion watermark is generated via diffusion,3D Cat transformation and DNA coding.Authentication watermark is generated via Latin square permutation and DNA coding.The dual fragile watermark embedding is controlled by the secret keys.The secret keys are produced by the chaotic map.The statistical results and security analysis show that this scheme can resist chosen cover-image attacks.