一种新的基于CRC的文本内容认证方法

提出了一种基于CRC的文本脆弱水印算法.利用CRC差错检测方法,该算法将要保护的文本按m个文字一个级联分成若干个级联,将每个级联与密钥合成后的位串除以设定的生成多项式,再把6位的余式位串分成三组,作为水印信息嵌入到级联的最后一个文字的RGB的三个分量.提取水印时,将该级联的余式位串求出.如果与提取的水印相同,则认为此级联没有纂改,否则有纂改.该方法检测到纂改的概率为1-1/26m,并且至少能将纂改定位于级联内.

A new text content authentication technique based on CRC

A new CRC-based algorithm of fragile text watermarking is proposed.Taking the CRC error detection method,the method divide the protected text into a number of m words cascade strings.Each cascade string and secret key consist a bit string,which is divided by a set generator polynomial.The residue bit string is divided into 3 groups(6 bits) assigning for RGB 3 components of the last character of the cascade string.The residue bits of the cascade string is also calculated at watermark detection.If residue bits of the character string is the same as the LSBs of the end characters RGB value within the cascade string,there is no tampering.Otherwise,there must be something tampering taken place. Our method can judge whether these cascade strings is falsified or not and locates the falsify in the cascades.Detection probability of the algorithm is 1-1/2~(6m).