Question How to find a Checksum in a Save File?

Discussion in 'Switch - ROM Hacking, Saves, Translations & Tools' started by Bedal, Oct 2, 2018.

  1. Bedal
    OP

    Bedal Member

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    Feb 28, 2016
    Gambia, The
    Is there someone who can explain,
    how to find a Checksum in a SaveFile?
     
  2. MichiS97

    MichiS97 "Leftist snowflake milennial"

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    Basically, save your game, make a backup, boot the game again, save right away, make a backup again. Rinse and repeat a number of times. Basically, make multiple savegame backups with only minor differences. Don't move your character. Don't collect any money. Try to make backups that are nearly identical to each other.
    Then compare all those backups in a hex editor of your choice and you should find a 16 or 32 bit value, different in each backup, probably near the beginning or end of each backup, which can't reasonably be associated to a time stamp or something. That might be your checksum.

    Then you'll have to figure out how the checksum is calculated. For that, it should help if you have knowledge about the overall structure of the save file. Usually, checksums are calculated over a specific range within the save file, usually disregarding some sort of header or the like. Try some common checksum algorithms, with different sectors of the files. Hex Workshop is a great tool for that.

    It's not a straightforward process. Every game is different. Good luck.
     
    Last edited by MichiS97, Oct 2, 2018
    Bedal, cold75 and Slade.AU like this.
  3. Bedal
    OP

    Bedal Member

    Newcomer
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    Feb 28, 2016
    Gambia, The
    Oh man. Dude that’s a lot work.
    But I will learn this. I trying to give my best Master! :D
     
  4. dsrules

    dsrules GBAtemp Psycho!

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    Sep 20, 2005
    if the value at 00000004 is the checksum, how do you get the new checksum value after editing the save file?
     
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