https://www.zhihu.com/question/24294477
只看了上面一篇的第一个回答，懂了百分之八十。
https://yq.aliyun.com/articles/54155https://www.zhihu.com/question/24294477/answer/93112599https://www.zhihu.com/question/24484809/answer/70126366
单双向https认证：
http://blog.csdn.net/duanbokan/article/details/50847612
