This is a new series about the cryptography challenges happened (and the challenges will be grouped into blog post quarter-yearly). I’ll be describing the challenge (or the cryptographic parts for the challenge) briefly. Also, I will not be walking through their solutions. In short, the series of the blog posts is served as a directory of crypto challenges happened in CTFs. The objective is to let CTF players on cryptography to identify challenges those they found interesting. In particular, the challenges marked with 🔥 are recommended.