Feistel 算法

學習資料：

https://www.jiamisoft.com/blog/8903-feisteljiegouhundunjiamisuanfa.html

https://blog.iwannarun.cn/2017/11/03/%E5%A6%82%E4%BD%95%E9%80%9A%E8%BF%87%E8%87%AA%E5%A2%9EID%E7%94%9F%E6%88%90%E5%8F%AF%E9%80%86%E7%9F%AD%E7%A0%81(%E9%93%BE%E6%8E%A5)/

https://my.oschina.net/u/2485991/blog/546946

https://my.oschina.net/u/2485991/blog/613920

https://blog.csdn.net/android_jiangjun/article/details/79378137