I would wish to learn more about checksums.

Discussion in 'NDS - ROM Hacking and Translations' started by Random Seeker, Mar 20, 2007.

Mar 20, 2007
  1. Random Seeker
    OP

    Newcomer Random Seeker Member

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    Any good guides to locating them, explaining how to recalculate them and such?
     
  2. FAST6191

    Reporter FAST6191 Techromancer

    pip
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    GBATek has all the data you want with regard to GBA and DS checksums for header info:
    http://nocash.emubase.de/gbatek.htm#biosmiscfunctions
    I used to use hex workshop and this was the stuff I had to put into the custom CRC to give the BIOS version of CRC16:
    [​IMG]

    If you are dealing with saves the hashes can range from parity to bytesums to crc16/32 to complex hashes of SHA1/md5 grade as well as complements of them. Although I have no examples (pokemon is a good bet for such things) I know other saves use inverted/shifted/XORed/some other operation and have it later in the save, the best way to find and calculate hashes in general (and especially nasty ones) is to use an emulator and monitor calls/access to save space and operations performed on it (most are able to boot a game far enough to determine this). With regard to determining what the save does the usual cheat finding approach can help.

    Oh and one last thing, a little while ago I responded to a similar post regarding save hacking and gave a similar response, the poster then ran the game in an emu and used a windows debugger to scan the memory and change it before saving the game once again, an approach I thought extremely novel.
     
  3. Random Seeker
    OP

    Newcomer Random Seeker Member

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    Thanks, I already have most of the required programs to hex edit and such, I'm fairly new to the DS hacking scene and still learning much from various sources.

    Edit: Well, after reading a TON of guides, what you have posted makes so much sense now, and from most save files I've seen, they do what you have mentioned above, the changes are not really visible until you save it once in game.
     

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