一种新的JPEG图像认证半脆弱水印算法

提出了一种用于JPEG图像认证的半脆弱数字水印算法，它根据JPEG图像压缩过程中的DCT系数的不变性原理进行水印生成和嵌入调制，并结合一种有效的算法隐性地考虑到所有非零DCT系数的符号、大小关系，在未增加水印信息嵌入强度的情况下，实现了图像应对变换域攻击的更有效保护。同时，在检测算法中加入对虚警区的判断，增加了对窜改区域定位的准确性。实验表明，该算法实现的水印有很好的视觉透明度，有效的承受JPEG压缩，同时对其他恶意篡改敏感并能够准确定位篡改位置。

New semi-fragile watermarking for JPEG image authentication

This paper presented a watermarking scheme for JPEG image authentication.The watermark was generated based on the relative sign and magnitudes of Discrete Cosine Transform(DCT) coefficients which were invariant due to an important property of JPEG compression.Combined with an effective method to include all the coefficients either explicit or implicit,the proposed algorithm improved its security level against malicious attacks in transform domain,without embedding more watermarking information in the original image.At the same time,an identification of false tampered blocks in the proposed authentication algorithm improved the accuracy of locating tampered areas.Analysis and experimental results are provided to demonstrate that the watermarked image possesses good perceptual transparence,and that the proposed algorithm takes JPEG compression as an acceptable manipulation.Meanwhile,it is sensitive to other malicious attacks and can locate the tampered areas.