Obscurity is a 30-point Linux machine on HackTheBox that involves exploiting a command injection in a custom webserver, breaking a simple cipher and abusing file system permissions to get root.
"Weakened Keys" was an interesting crypto challenge on InfernoCTF.
Using the hill cipher cracking theorem to solve the ctf challenge.
Kryptos is 50 points machine on hackthebox, involving some interesting techniques, like setting up a fake database and making the application use it, abusing a weak rc4 implementation, pivoting through a web application and injecting into a sqlite database. In addition we exploit a weak prng on a application which...