Checksum on Save Files

[NiteKat]

Hello, I am working on a project around save files for WoTL, and am having some issues with the checksum of the file after saving modifications. If you just change the data on a save, then attempt to load it you get a message that the save is corrupt, but loading it in Lion Editor and saving makes it usable again. I found there's a section that appears to act as a check sum when certain data is modified, and Lion Editor seems to generate proper check sums, but I cannot find any information on how it's generated so I can do so in my own project, without having to involve Lion Editor. Is anyone familiar with how this works?