密码学与数字水印在电子印章中的应用

为了提高电子印章和电子公文的安全性，以及方便电子公文的推广使用，文中结合公钥密码学和数字水印技术设计了一种具有三层结构多重水印的电子印章，给出了印章制作的方法并介绍了系统的组成结构。其中的表现层作为要素显现，使电子印章符合传统的使用习惯；脆弱的半透明可见水印层具有防复制、防篡改功能；第三层嵌入稳健的不可见水印，使印章具有惟一性。同时将私钥存储在智能卡上，含水印电子图章存放在电子印章服务器中，从而进一步提高了整个电子公文系统安全性。

Application of Cryptography and Digital Water-Mark in Electronic Cachet

To improve the safety of the electronic cachet and the electronic documents,design a schema of three layer watermarking with the combination of cryptology and digital water-mark. The presentation layer shows the picture of the electronic cachet.The half transparent crisped watermark can protect from being copied and tampered. The last layer have a strong invisible watermark for the uniqueness.Use the smart card to store the secret key, and save the cachet image into the cachet server to improve the system safety. In the end,introduced how to make the cachet and the design of the system.