Unofficial writeup:
- https://paper.seebug.org/755/
- http://f1sh.site/2018/11/25/code-breaking-puzzles%E5%81%9A%E9%A2%98%E8%AE%B0%E5%BD%95/
- https://www.cnblogs.com/iamstudy/articles/code_breaking_writeup.html
- https://blog.l0ca1.xyz/Code-Breaking
- http://www.kingkk.com/2018/11/Code-Breaking-Puzzles-%E9%A2%98%E8%A7%A3-%E5%AD%A6%E4%B9%A0%E7%AF%87/