对水印信息篡改鲁棒的自嵌入水印算法

为提高自嵌入水印算法在任意篡改条件下的篡改恢复质量,提出一种对水印信息篡改鲁棒性的空域自嵌入水印算法,分析了算法中阈值选取的合理性和检测篡改的可靠性.该算法首先基于密钥将原始图像的最低位和1/4次低位置零,通过对图像内容的小波低频系数实施均匀标量量化生成低频特征图像,将低频特征图像置乱加密后生成的二值编码嵌入原始图像的置零位;认证时通过设定的阈值识别图像内容被恶意篡改的图像块,从而提高自嵌入水印算法对水印信息篡改和信道噪声的鲁棒性.理论分析和仿真结果表明,无论水印信息被随机篡改还是区域篡改,算法均能根据阈值区分不同篡改并选用不同的方法对其进行篡改恢复,有效地提高了自嵌入算法在部分水印信息篡改时的恢复质量.

Self-Embedding Watermarking Algorithm with Robustness against Watermark Information Alterations

To improve the quality of the reconstructed image in any tamper condition, this work proposes a self-embedding watermarking scheme with robustness against watermark alterations, and discusses the reasonability of the predefined threshold and the reliability of tamper detection. The proposed scheme firstly sets the least significant bit (LSB) of three-quarter pixels and two LSBs of the residual pixels in the original image to zero. And then the low-frequency feature image is obtained by quantizing the low-frequency wavelet coefficients of the original image content. The improved security watermark, which is the binary code of the scramble version of the low-frequency feature image, is embedded into the LSBs which were set to zero. While the image authentication, the proposed method is able to discriminate the malicious modifications from the mild distortions according to the predefined threshold to enhance the robustness against innocuous alterations such as watermark changes and channel noise. Theoretical analysis and simulation results show that the proposed scheme can discriminate the different modifications according to the predefined threshold no matter the embedded watermark in the host image is randomly or regionally tampered. The quality of the recovery image can be effectively improved due to the fact that the different reconstructed methods are adopted for the different tamper blocks.