Quote from: WelshPaul on June 26, 2015, 03:56:48 AM
Can you post how to get around the checksum?
Would like to try this myself.
There is no standard way of computing a checksum. Variables include which part (if not all) of the file it is calculated from, its size (usually 8 or 16 bits) and where the expected result is placed.
Simple schemes just XOR every byte or word but others like md5 and sha1 could be used.
Most times the checksum is to provide some protection against the device being flashed with a corrupt file rather than trying to prevent 'hackers' from meddling so the level of obfuscation is frequently low and determined educated guesswork plus trial and error will crack it. Currently, I'm not feeling sufficiently motivated to have a go at it.
If you want to try it, here is one approach which might work. Assuming you can find the bytes which hold the version number, are there two which you can swap (replace each with the other) such that the version number will be higher? The file length will be unchanged and an XOR checksum over bytes will be unchanged.