ROM Hack I there any way to calculate the crc hash?

[Ismaw34]

Hello,

I'm experimenting with the nds saves, and i found that some sav files contains a crc hash at start of the file.

Header:0x0
Lenght: 4 bytes
Description: CRC32 hash?

Is there any way to recalculate the hash when i edit the file to prevent "save corruption"?

Thanks.

 

[FAST6191]

Hashes/checksums used in save games can vary widely -- for the DS I have seen it range from cryptographic grade stuff like SHA1 and MD5 and go right through to basic bytesums, likewise the CRC stuff can be a bit custom and if nothing else trying to figure out what area is hashed can be annoying. It tends to fall on the more basic side of things, after all it is just a save and anything drastic takes time to do.

There is no easy way to figure out an unknown checksum, some get lucky but others have to watch it happen and replicate that. Few people reinvent the wheel though so as long as you know roughly how something in the CRC family is calculated, the idea of parity, bytesums are usually blindingly obvious when you look at them in a debugger and maybe something a bit more exotic you should be good.

If you prefer, or if you are otherwise making a save editor, you can break the game's has check. This means the game will run the check but regardless of whether it works or fails it will continue on.

 

[Ismaw34]

Im making a wfc patcher for layton3 and 4 games.
I have the files with downloaded puzzles and the same without them.
The problem is the crc hash at the header.

I dont know how to disable the check, as the first 2 dont have them and i have a ips patch that does the work.

I was planning to release the app when i figured out the crc thing. But, anyways, thanks.