https://program-think.blogspot.com/2014/11/https-ssl-tls-1.html
https://program-think.blogspot.com/2010/02/introduce-digital-certificate-and-ca.html
http://www.ruanyifeng.com/blog/2014/02/ssl_tls.html
http://op.baidu.com/2015/04/https-s01a01/
http://blog.jobbole.com/110354/
http://www.jianshu.com/p/54dd21c50f21