1Title: SSL/TLS单向认证流程
 2Client->Server: (1) Client Hello (随机数、client端支持的加密算法)
 3Server->Client: (2) Server Hello (随机数、选择一个client支持的算法)
 4Server->Client: 下发Server证书
 5Client->Client: (3) 验证证书
 6Client->Server: (4) Client Key Exchange (用Server公钥加密Pre-Master key(通过Client Server协商后得到的key))
 7Client->Server: (5) Change Cipher Spec (通过Server参数协商完成)
 8Client->Server: Finish handshake (Encrypted Handshake Message)
 9Server->Client: Cipher spec + Finish handshake
10
11Client->Server: ...
12Server->Client: ...