Sorry to bump this thread, but it seems like the appropriate place to ask this question.
People have posted mods for zombies like super jump and super speed, and to install it you just copy in the 3 files EBOOT.BIN, common_zombie_patch.ff, and t5_ps3f.self.
How do they patch the fast file for zombies and the other files? Is the private key and public key not needed? And how is it done? Seems like a start of something...