Krypton3
Website: http://overthewire.org/wargames/krypton/krypton2.html
According to the website page, this level involves a Caesar cipher
Let’s login using krypton2 credentials

Let’s see the contents of the README

Let’s create the working directory and provide access as mentioned in README

Let’s create local file containing a string ABC, encrypting this file should give us the offset of Caesar cipher.

So, ABC translates to MNO, meaning the offset is 12. Let’s use this offset in the ROT13 program we whipped up earlier.
So, we have our credentials!
Username: krypton3
Password: ************