Trying to build community game patch, what encoding/encryption does PSP ISOs use?

[ACmod]

I'm trying to make a community patch for Armored Core Last Raven Portable (either in the form of an ISO or a CWcheats patch) that changes some of the stats of various parts to balance the game better.

I have tried using cheat engine to search the game data and have been completely unsuccessful in making a single cheat that does anything (including crashing the game! Nothing. No cheats I make have any effect.)

So next, I tried to see if I can edit the game ISO directly by unpacking the ISO and viewing the binaries. But it's just a wall of nonsense in both hex and binary.

What encryption or encoding do PSP games use, for developers to modify them? If I want to patch an ISO or make changes to a game, how do I de-encrypt a game file to modify the .BIN files?