易损数学水印算法可用于多媒体内容真实性的保护。为更有效地设计和使用易损水印，首先通过研究其算法应具有的特点及易损水印与鲁棒水印的差别；然后在可信赖的数码相机这个应用背景的基础上，提出了一个简单的易损水印应用框架；最后，讨论了变换域易损图象数学水印算法的误差问题和逆变换后象素值溢出的问题，同时给出了两种解决方法，并利用此方法对一种基于小波变换的易损水印算法做了改进。

In this paper, we discuss several problems on fragile watermarking, which is used to ensure the credibility of multimedia. Firstly, we describe some main properties that an efficient fragile watermarking scheme should have. And then we discuss the differences between robust watermarking and fragile watermarking algorithms, which are important for us to develop efficient fragile watermarking scheme. Thirdly, a simple application framework for fragile watermarking, which is called trustworthy digital camera, is proposed. This fragile watermarking framework can be used for ensure facticity for images taken by digital camera. In the end, we present two approaches, pre processing and using integer transform, to solve round off error and overflow error problems for frequency domain fragile watermarking techniques. Experimental results show that these two approaches are efficient for improving other fragile watermarking algorithms.