Rockbox Development > New Ports
Creative Zen Vision:M
Transience:
Couldn't you use a memory editor or debugger to search for the checksum while the updater is running? If it turned up, it would seem to indicate that both firmware and updater use the same checksum algorithm.
iSE:
Well the firmware wont have the algorithm in it, it only has the checksum stored on the end of it. The last 20 bytes. If anyone is good at making mathematical scripts there is a task which may help.
We are assuming that the checksum is either, SHA-1 (or one of the 3 variants), or maybe even SHA-0. I cannot find the psuedocode for SHA-0 but if anyone can make a program which calculates the SHA-1 checksum from the psuedocode available at wikipedia: http://en.wikipedia.org/wiki/SHA_hash_functions#SHA-1_algorithm, including the 3 different variations of it, just to confirm if it is or is not one of these. You wouldnt need to worry about doing anything with the checksum, literally just to create a program which calculates 4 different checksums from a file. (nk.bin without the NULL block)
Bagder:
sha1sum has been around for ages and while it presents "just" one sha-1 sum, I figure it could be a nice start to get the other alternatives tested out too...
iSE:
exactly, all the calculators out there only calculate the main one, so that mite be why its not coming up as a match. Creative may not be able to fund their own algorithm so will use a less known one. Its a good start and something to eliminate. If anyone can find any information on the SHA-0 algorithm aswell, that would be useful.
Transience:
--- Quote from: iSE on July 12, 2007, 06:20:12 PM ---Well the firmware wont have the algorithm in it, it only has the checksum stored on the end of it. The last 20 bytes. If anyone is good at making mathematical scripts there is a task which may help.
--- End quote ---
If that's true then the player can't checksum the firmware being passed to it, and should accept any firmware that is uploaded to it.
The checksum algorithm may also be skipping parts of the firmware file when calculating the checksum, making the job of finding the right algorithm even harder.
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