http://www.cnblogs.com/chyingp/p/https-introduction.html
http://www.cnblogs.com/heart-runner/archive/2012/01/30/2332020.html
http://www.ruanyifeng.com/blog/2014/02/ssl_tls.html
http://blog.csdn.net/bluishglc/article/details/7585965
