Encrypted or compressed?

[VeggieGames]

In working towards decoding the PSP executable files I was taking a look at the savegames. We don't know if they both use the same encoding but for now we'll assume that's the case.

Anyway, I think I've determined that the savegame files (at least the ones for Wipeout) are not compressed, only encrypted. The way I tested this was by creating two different savegame profiles in Wipeout Pure. In the first I entered my name (Johnathan), which wouldn't compress very well. In the second I entered a name that would compress, specifically AAAAAAAAA. Both are the same number of letters. I didn't play through the game for either profile, only created them and set the same options. I looked at the savegames afterwards and both were the exact same size, which means they are not compressed because the one with the name of all A's would be a few bytes smaller if that was the case.

Is anyone else able to do a similar test with other games? If all the other savegames are also uncompressed then that narrows down what we need to try for decoding.

[Orion_]

I read a post about this somewhere, so yes, someone has already done this test.
it was with ridge racer and the japanese rpg game I think, can't remmember the name

[KiWi]

In a good encryption algo you just change 1 bit in the source file and the destination file differs completely.

AES is such kind of encryption. This is not a "do a xor / ror " over the data and gotcha ... AES is hacking/cracking proof.

If no one spents alot of $$$ money $$$ to hack the custom chips and extracts the aes key, you'll never see a homebrew app that starts over the easy way.

The only real chance is to find a massive bug / exploit to intrude the system and bypass the psp security checks ...

I won't bet 50 cents atm that any1 will find such a bug and intrudes the system :/