Abstract: By analyzing the limitation of the traditional image authentication schemes,a novel scheme entirely based on chaos is proposed for digital image authentication.A piecewise linear chaotic map is utilized to generate the look up table (LUT) and the parameter of two-dimensional Cat chaotic map,which is based on the image feature.The Cat map is used to pre-permutate the original watermark with diffusion mechanism.On the foundation of LUT and the diffused watermark,the embedding can be completed.While the watermark extraction and authentication are very simple.The performance analysis and simulation demonstrate that the whole scheme is secure,efficient,and practicable,with simple structure and strong ability of tamper localization.