关键词: 混沌, 认证水印, 脆弱, 篡改定位

Abstract: Concerning of the issue that the present fragile authentication algorithm’s positioning is on a low accuracy and security condition，a complete fragile watermark algorithm which is based on the chaos has been put forward and has been used to certificate the integrity of the image content and locate the tampering. The algorithm uses the methods to separate the original image into blocks，then to calculate the high 6-bit gray-scale for the mean of each pixel in a block of image as the image characteristics watermark information. It also uses chaotic sequence to encrypt watermark information and determine the location of each embedded watermark bit，tampering with positioning accuracy for the 2×2 pixel image block. Experimental results show that the algorithm is simple，safe，and has a good practicality.

Key words: chaos, authentication watermark, fragile, tampering location