Rockbox Development > New Ports
Creative Zen Vision:M
Bagder:
--- Quote from: iSE on July 15, 2007, 04:30:37 AM ---Why do you all assume that the algorithm is in the firmware? I won't be, the checksum, as in the hash key will be stored in the firmware file and we think its the last 20 bytes of the nk.bin file.
--- End quote ---
Indeed. But the update program might have the checksum algorithm to verify the image before trying to upgrade to it (just to be able to "warn early").
--- Quote ---its so hard to make a secure algorithm I also doubt they would ever change it.
--- End quote ---
People don't just invent their own algorithm (if they are clever), they use one of the already established and proven very reliable algorithms. And out of all players rockbox runs on, very few have the ability to change the algorithm.
iSE:
--- Quote from: Bagder on July 15, 2007, 04:56:40 AM ---Indeed. But the update program might have the checksum algorithm to verify the image before trying to upgrade to it (just to be able to "warn early").
--- End quote ---
I agree, and I indeed said that its possible the calculating algorithm is in the updater program just not in the actual firmware file itself (the nk.bin) which is what is transferred to the player.
--- Quote from: Bagder on July 15, 2007, 04:56:40 AM ---People don't just invent their own algorithm (if they are clever), they use one of the already established and proven very reliable algorithms. And out of all players rockbox runs on, very few have the ability to change the algorithm.
--- End quote ---
Again I agree, but if you modify the algorithm slightly it can create huge security holes which is why modifying the algorithm would be out of the question. And if we assume the 40digits at the end of the nk.bin are the checksum, there aren't that many 160bit encryption algorithms out there so they will probably not use a different one each time. My guess is, they always use the same algorithm, obv not SHA-1 or SHA-0 because mcuelenaere checked. Did you check for the variations on the SHA-1 algorithm? There are 3 alternatives to calculating one of the values which are just as secure. So they may have used one of those as then none of the calculators would give a match as they'll use the main psuedocode.
phcoder:
I changed 67->77 in the first SHA-1 constant. The updater no longer recognizes the player and asks me to connect it even if it's connected. I will do further debugging with softice
bgdwie:
ok, so, this may have already been said, but, why doesn't someone get a usb data logger run it whilst doing a firmware update, it will record all packets sent and received via usb, it should give us an idea of what is going on, it might help, it should turn out some pretty interesting info...
phcoder:
BTW. Has somebody thought about padding? To day or tomorrow I'll reverse engeneer SHA-1 related part of updater (I already have some experience with this kind of things)
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