面向医学图像的篡改检测双重水印算法

Double Watermarking Algorithm for Tamper Detection of Medical Images

针对医学图像中嵌入水印信息造成的鲁棒性与透明性的不平衡问题,提出了一种面向医学图像的篡改检测双重水印算法.首先,采用Sine-Cubic混沌映射加密算法将Sine映射与Cubic映射进行线性耦合,利用得到的混沌序列对版权图像进行加密.其次,对载体图像进行小波变换,并对低频子带进行安全区域划分,根据安全区域内子块熵值将医学图像划分为感兴趣区域(ROI)和非感兴趣区域(NROI).同时,通过提取ROI的稳定特征与加密的版权构造鲁棒的零水印.最后,将零水印嵌入医学图像NROI子块Schur分解的上三角矩阵最大系数中,同时记录嵌入水印后的最大系数用于篡改检测.实验结果表明:所提水印算法具有不可感知性、鲁棒性和安全性,同时可以准确地定位被篡改的含水印区域;与其他水印算法相比,所提双重水印算法在鲁棒性和算法效率上均有很大的提升.

A double watermarking algorithm for medical image tamper detection is proposed to address the imbalance between robustness and transparency caused by embedding watermark information in medical images.First,the SineCubic chaotic map encryption algorithm is used to linearly couple the Sine map and Cubic map,and the obtained chaotic sequence is used to encrypt the copyright image.Second,the carrier image is wavelet transformed,and the lowfrequency subband is divided into safety regions.The medical image is divided into regions of interest(ROI)and noninterest(NROI)based on the entropy value of the subblock in the safety region.Simultaneously,a strong zero watermark is created by combining the stable features of the ROI region and the encrypted copyright.Finally,the zero watermark is embedded into the maximum coefficient of the upper triangular matrix of Schur decomposition of the NROI subblock of the medical image,and the maximum coefficient following the watermark embedding is recorded for tamper detection.The experimental results demonstrate that the proposed watermarking algorithm is imperceptible,robust,and secure,and can accurately locate the tampered watermarked region;when compared to other watermarking algorithms,the proposed double watermarking algorithm is significantly more robust and efficient.