Based on the good randomness and extreme sensitivity to initial value of the chaotic transformation,we propose a new tamper-resistant fragile digital watermarking algorithm with the function of precise positioning. The algorithm makes use of the low-frequency and middle-frequency of DCT coefficients weighted by chaotic sequence as image characteristic information,and generates fragile watermarking sequence by chaotic transformation,and then it embeds fragile watermarking sequence in the middle-frequency DCT coefficients. Experimental results and theoretical analysis show that the algorithm almost does not affect the visual quality of the image,and the tamper region can be detected effectively and positioned accurately,and the source image is not required in the process of the watermarking information extraction and verification. The proposed algorithm not only improves the precision ratio of positioning the tamper region,but also reduces the ratio of false positive and false negative.%基于混沌变换良好的随机性和初始条件极端敏感性,提出了一种精确定位篡改位置的脆弱混沌数字水印算法.该算法将混沌加权后DCT中低频系数作为图像特征,利用混沌DCT匹配块对生成脆弱水印序列,最后嵌入到图像的DCT中频系数中.实验结果与分析表明,该算法几乎不影响图像的视觉质量,对图像篡改区域具有检测有效性和定位准确性,实现了盲认证.该算法不仅提高了篡改定位的精度,虚检率与漏检率也相应降低.
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