OverTheWire bandit is really fun. I was able to get up to the level with the encryption stuff. The encryption stuff confused the hell out of me.
Be sure to use the manuals and the wiki entries about the relevant commands listed on the website. You need to use some comprehensive reading and crack your brain. It is quite literally a puzzle. Not much I can say to you to help you without spoiling the puzzle.




But… thats also just a license. Any use except for the creator necessitates a license of some sort or the release to the public domain.