This article studied and has realized in the symmetrical password system DES algorithm, the male key password system RSA algorithm with emphasis and uses in the digital signature MD5. algorithm, has made the secure analysis.

• 本文重点研究并实现了对称密码体制中的DES算法、公钥密码体制的RSA算法和用于数字签名的MD5算法，作了安全性分析。