Savegame Checksum Expirience ?

[LordIcon]

Hi,
iam currently working on hacking a Xenosaga Savegame. I transferred it via nPort.
finding the right values for the charackters in the save was pretty easy, by just comparing 2 savegames with the according value changed.
Editing these values does not work, because the savegame seems to be checksum protected.
i was able to figure out the place where the Time ( since gamestart) is stored, as it changes even if nothing else is changed between gamstart.
There are some other bytes at the beginning of th file that also change., i suggest this is a checksum, but i was not able to match any generated checksum ( i tried checksum 8-64 , CRC16, CRC32 , some MD checksums) .. its a pain i the ass to find the portions of the save that are used to calc the checksum.

The question i have now, is there anybody who has docs or other info about recently used checksums or any other info about standards uses in Memory Card Save ( specially Namco, Squaresoft) ..

[GMO]

you need a checksum bypass code, i have one for the japanese version, i could get one for the american version if you need it

[LordIcon]

if you are talking about a CodeBreaker/ActionReplay Code this will not work for me, this diables the check in the game and is not what iam looking for. I need to be able to make the savegame look correct. But thanx for the help

[gothi]

You could try using Checksum Repair, let me know how you get on with it

[LordIcon]

Thanx for the proggy, but it does checksum calcs for PSU or PSD Files (what Prg creates these btw ?), which i dont have, i used Nport, that gives me .npo files which i extract and pack using the npo-x tool that comes with Nport.
I don't think there is a problem with a checksum in these .npo files, and if so, it should be calculated by the npo-x tool as soon as i pack the content of the .npo together again. ( maybe as Napalm about it)

Besides , the Proggy is somewhat hard to use, cuz of all the japanese chars in it...

I think there is a checksum in lets call it the "user"-Data in the Xenosaga savegame, that is checked before displaying the save in the load/save Menu.

Its hard to find a checksum if you don't know in which part (startaddress,length) of the file it is and if you don't know how it is calculated and what parts of the file a relevant for the calculation.

So i was thinking , someone maybe had put some brains in that , or has analysed other savegames , concerning used technics.

[Spudz777]

Not sure if you still need this, but if you got GMO's code to open the save, disable the code, and then saved the game, it would recalculate the checksum and it would "look right". The only problem then is if you (like me) don't have a CodeBreaker or ActionReplay then you're either spending more money or you're out of luck...