Calculate exFAT checksum

Started by PokePango, June 09, 2016, 10:24:07 AM

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PokePango

Hello,

I'm want to re-calculate the checksum of a disk's VBR but I can't get the good result, when I plug it into Windows I get a fatal error and the disk isn't recognized.

I saw this topic related to ML: https://groups.google.com/forum/#!topic/ml-devel/EWHU5ukyMt4

But it doesn't works... I also tried to copy/paste the related sectors directly into the script (with an hexa editor) but still the result isn't correct. Am I missing something? I copy the data from sector 0 of the VBR (offset 2048 on my disk) up to sector 10 which corresponds to 5632 bytes, calculate the checksum and don't have the right result!

Can anyone help me? Thanks!

Overcertified

If you are doing what you say, then you are doing it wrong.

In the first VBR record there are I think 3 bytes that are excluded ftom the calculation.

There is information on in Robert Shullich sand paper and a program on his blog at rshullic.Wordpress.com where you can extract the algorithm as well.