Homebrew developer Hellcat dropped by QJ.NET PSP Development Forum and released a plugin for custom firmwares that is highly reminiscent of the good ol' FW 1.5 days. The program itself is known as Savegame Deemer.

In a nut shell, this allows the PlayStation Portable to save any savedata in unencrypted form as well as the normal way. An unencrypted savedata, as you know, can be directly edited with a number of different tools like hex editor for example.

Hellcat mentioned that except for intentional delays during loading and saving to prevent conflict with other threads, there are currently no known negative side effects that come with Savegame Deemer. To make things clearer, here are its other functions when active:

• If unencrypted savedata for the current load is present it will be loaded instead of the normal/encrypted one.
• When saving, there's always the unencrypted version saved alongside.
• If no unencrypted data exists for the current load, the normal/encrypted one is loaded as if nothing ever happened.
• So, if you want to use your normal savedata again, either disable this plugin or delete the unencrypted version from /PSP/SAVEPLAIN.