基于DCT变换的脆弱水印技术

A Fragile Watermarking Technique Based on DCT Transform

提出了一种用于图像鉴定的脆弱水印方法。该方法首先对图像进行8×8分块,计算每一块的DCT值,然后选择所要保护的区域,确定完全属于该区域的分块,并提取这些分块的特定位置的低频分量,采用Hash函数加密生成相应的具有固定长度的数字摘要,然后选取该数字摘要的若干位作为脆弱水印,并把其隐藏到该区域其余的DCT分块中去,以实现水印检测时不需要任何额外信息,试验表明这是一种行之有效的图像鉴别方法。

This paper proposes a fragile watermarking method for image authentication,in the method,the original image is firstly divided into 8×8 blocks,then choose the region to be protected.It calculates the DCT for each block and choose blocks completely belonging to the region,gets the lowest frequency components of specific positions from the blocks chosen,then encryptes them by the Hash function which generates the message digest with fixed length;chooses some bits of the message digest as the fragile watermark and hides it into other DCT blocks of the region in order to implement watermark detection without needing the original image.Experiments show that implementing image authentication using this method is very useful.