Effective multimedia authentication is an increasing important issue in a networked environment. Fragile digital watermark thus come into being. Unlike traditional digital signature which is bounded with the content

fragile watermarking works effectively for multimedia content authentication by embedding a watermark(such as identification data

serials number

text or image etc.) to multimedia documents without influencing the vision or hearing effect of multimedia. Fragile digital watermarking is of great importance in courtroom defence

reliable e-business

medical image databases

etc. When the conetent of multimedia is suspected

the extraction of fragile watermark can be used to detect and localize tampers

even present the category of tampering. To motivate the relative research in this field

we attempt to give a brief overview of fragile digital watermarking into the context of image authentication in this paper.The basic characteristics of fragile watermarking is first outlined.Then comes the discussion of current algorithms

which not only includes basic schemes--spatial domain based algorithms and transform domain based methods

but also sums up the four typical types of fragile watermarking with different applications. Possible attacks and future research topics come in the following and future direction is outlined in the end.There still need a long way for fragile digital watermarking to go into standilization and actual applications.