A secure image authentication scheme based on dual fragile watermark

Both security and tamper localization are essential for fragile watermarking techniques. Embedded fragile watermark should be sensitive enough to cover images. But high sensitivity maybe bring inaccurate tamper localization, and both high sensitivity and accurate tamper localization seem contradictory. This paper proposes a watermark scheme based on dual fragile watermark: diffusion watermark and authentication watermark. The diffusion watermark is determined by a cover image, a secret key and two random numbers via nonlinear transformations, and the authentication watermark is generated from the cover image, the diffusion watermark and another secret key. The diffusion watermark and the authentication watermark have high sensitivity to cover images and at meantime the authentication watermark can verify the integrity of images and localize tampered area. The scrambled authentication watermark and the diffusion watermark are arbitrarily embedded into the two lowest significant bit layers of the cover image through a random sequence controlled by a secret key. The design aims to enhance the security of fragile watermarking, and the statistical results and security analysis show that this scheme can resist chosen cover-image attacks.