关键词: 图像认证, 篡改定位, 混沌系统, 脆弱水印

Abstract: A fragile watermarking algorithm based on a chaotic system is proposed for color image authentication，it divides the image into non-overlapped blocks，calculates the luminance of each block to decide the embedding depth and the length of chaotic sequence.For each pixel，an initial value is determined based on its prominent chrominance value，the position index，and the image protection key.Watermarking sequence is embedded into the embedding space of R，G，B respectively.Then it detects the temper by comparing the extracted watermarking and the produced one，so the error image is attained.Theoretical analysis and experiment result show that this algorithm to be in high quality and locate the tamper position exactly.

Key words: image authentication, tamper location, chaotic system, fragile watermarking