自己用Java编的Client-Server聊天程序，结合了网络通信、数据安全、多线程的知识

1．使用RSA算法完成DES密钥的分配；

2．使用MD5结合RSA算法完成对消息的签名；

3．对原有消息及签名提供机密性保护(用DES算法加密)；

4．能够解密并验证签名的合法性

-Their use of Java made the Client-Server chat program, a combination of network communications, data security, knowledge of multi-threaded one. RSA algorithm using the completion of the distribution of DES keys　2. RSA algorithm combines the use of MD5 message to complete the signature　3. The original message and signature to provide confidentiality protection (with DES encryption algorithm)　4. Able to decrypt and verify the legitimacy of the signature