There are two types of coding dev uses, which are not really mathematically complicated if you know how they work.
One is "shift letter right on alphabet X times where X is a position in word". Simply saying if you have word "aaa", first "a" becomes "b", second one becomes "c" and third one becomes "d", resulting in "bcd". That's why you don't see same letters repeat in encoded string. You can see those in "dec" section on my screenshot.
Another one is a little bit more complicated. It does the same "shift right" strategy, then converts each letter to its ASCII hex-code (for example, "2" is "32", "h" is "68"), then each "3" is replaced by "x", "6" by "y" and "7" by "z" ("f" -> "66" -> "xx"). Those are in "enc" section on my screenshot.
There is also some portion of hardcoded pieces added during encoding, which act as a garbage data to distract anyone trying to decipher. But important bits like user login and game version are directly encoded as-is.
Btw, screenshot contains couple of working NSFW passwords too, though without enabled cheats.