Novel semi-fragile watermarking algorithm for image content authentication

A novel semi-fragile watermarking algorithm was proposed to improve the accuracy of image content authentication. This algorithm introduced the conception of relevant-block-group, and divided each relevant-block-group into several sub-block-groups, generated the watermark information by using the particular block of the each sub-block-group by turn, finally, embedded the watermark into the other blocks of the sub-block-group. This algorithm selected the watermark quantization steps self-adaptively according to the content feature of the host image, finished the embedding process by combining the high energy concentration of the Slant transform and the principal of direct current coefficient quantization. Moreover, a noble noise-filtering strategy was proposed, and the voting method was applied to position the tampered area in the authentication process. Experimental results show that the proposed algorithm can improve the quality of the watermarked image effectively and prevent the watermark detection without authentication, and it can also significantly enhance the positioning accuracy when facing with conventional treatments, such as cutting, replacing, and etc. The algorithm has good ability of resisting accidental attacks, and the new noise strategy improves the recognition effect of the tampered region effectively.