用于图像认证的变容量恢复水印算法

兼顾水印嵌入容量和安全性,提出一种水印容量可变的数字图像可恢复水印算法.该算法提取2×2图像块特征生成变容量恢复水印——平滑块6比特,纹理块12比特.图像块的恢复水印基于密钥随机嵌入在其它图像块的低有效位,通过比较图像块特征与相应恢复水印重构的块特征并结合邻域特征判定图像块的真实性,变容量恢复水印用尽可能少的比特数保存足够的图像块信息,仅被嵌入一次且同时用于篡改检测与恢复,不仅有效降低了水印嵌入容量,而且提高了算法抵抗恒均值攻击的能力.实验仿真结果表明,该算法得到的含水印图像和恢复图像的质量好,且能有效抵抗拼贴攻击、恒均值攻击等已知伪造攻击.

Variable-Payload Self-Recovery Watermarking Scheme for Digital Image Authentication

This paper proposes an image self-recovery fragile watermarking scheme with variable watermark embedding capacity.Both watermark embedding payload and security are taken into account.For each block of size 2×2 pixels,the features are extracted to generate the recovery watermark with different length——6 bits for a plain block and 12 bits for a texture block.The recovery watermark of an image block is inserted into the less significant bit planes of the other block based on the secret key.The validity of a block is determined by comparing the features computed by the block content with the ones reconstructed by the corresponding recovery watermark incorporating with its neighbor characteristic.The variable-capacity recovery watermark contains the adequate information of image block to as few bits as possible.The recovery watermark is inserted in the original image only once,and used to both tamper detection and tamper recovery in the proposed scheme.These strategies make the watermark embedded payload as low as possible and the ability against the constant-average attack to be improved.Experimental results show that the proposed scheme not only has the better quality of the watermarked and recovered images,but also resists the known counterfeiting attack such as the collage attack and the constant-average attack.