基于等级结构的多重图像认证水印算法

Image Multi-Authentication Watermarking Method Based on Hierarchical Structure

提出了一种基于等级结构的用于多重图像认证的脆弱水印算法.根据等级结构,将原始图像划分为多等级子块,然后对各等级子块进行独立的水印生成和嵌入.将混沌调制后的像素值映射为混沌系统的初值,经过混沌迭代生成水印信号,然后将水印信号替代像素的最低有效位,完成水印的嵌入.文中提出了一种新的水印分配方法,通过引入一个可变参数来控制各等级图像块对应的认证水印长度,分析了在该分配方式下水印定位精度和安全性之间的矛盾.实验结果表明,提出的水印分配方法可以有效地提高等级水印算法的性能,选择合适的划分等级可以取得定位精度和安全性两方面的良好性能.提出的等级水印算法能对图像的篡改进行多重检测与定位,极大地提高了脆弱水印算法在实际应用中的灵活性.

A fragile watermarking technique for image multi-authentication was proposed in this paper. According to the hierarchical structure, the image was divided into blocks in a multi-level hierarchy. Then we calculate and embed the block watermarks in each hierarchy, respectively. The chaotic inodulated pixel values were mapped into the initial value of the chaotic system, and then the watermark can be obtained by iterating the chaotic system. The least significant bits of pixels were substituted by the watermark to obtain the watermarked image. A novel assignment of watermark capacity was presented in this paper. A variable parameter was designed to control the length of signatures for each level block, and the conflict between the tamper localization accuracy and the security of the hierarchical watermarking method is analyzed. Simulation results show that the proposed assignment method can effectively improve the performance of hierarchical watermarking algorithm. The partitioning level can be chosen to make the hierarchical watermarking method obtain a good compromise between the tamper localization accuracy and security. The hierarchical watermarking method can detect and localize content modifications with multi-level authentication, which makes the watermarking method flexible in actual applications.