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Quote from: z80man on December 30, 2010, 02:05:29 amQuote from: Builderboy on December 30, 2010, 01:32:15 amNow correct me if i'm wrong but if we swap two bytes, the checksum should be the same and the program should run right? However it would fail if one of the bytes was the checksum right? Maybe this could be used to find out where the checksum is if we don't know it already?Yes if we swap two bytes programs still run. Also at address 0x0020 there is a checksum of the program, but it excludes a few bytes which I have not found yet. There is also a checksum of just the first 32 bytes of the header, but i hav not found that either. So far though most of the header is cracked. Currently I'm writing documentation file for the entire app header which is $7000 bytes long. If we're lucky we could get a test NOP app running before the year ends.That's awesome, really. I wish I had a prizm, because I would write the program to test the checksum for you, and have it automatically try and resent it. It shouldn't be too hard.I'm eager to try and break the usb protocol. If anyone wants to give me a data logging for usb, and the file that they sent/received, I would be very happy, and would try and analyze it. (Simple USB Logger file is a free logger, or of you can log the bytes to a text file, that would be fine, too.)
Quote from: Builderboy on December 30, 2010, 01:32:15 amNow correct me if i'm wrong but if we swap two bytes, the checksum should be the same and the program should run right? However it would fail if one of the bytes was the checksum right? Maybe this could be used to find out where the checksum is if we don't know it already?Yes if we swap two bytes programs still run. Also at address 0x0020 there is a checksum of the program, but it excludes a few bytes which I have not found yet. There is also a checksum of just the first 32 bytes of the header, but i hav not found that either. So far though most of the header is cracked. Currently I'm writing documentation file for the entire app header which is $7000 bytes long. If we're lucky we could get a test NOP app running before the year ends.
Now correct me if i'm wrong but if we swap two bytes, the checksum should be the same and the program should run right? However it would fail if one of the bytes was the checksum right? Maybe this could be used to find out where the checksum is if we don't know it already?
Well, it's so good at pretending that it will even give up its internal data like a USB device
Sauce?
Offset(h)00000000 ë<.MSDOS5.0.....00000010 ...v€ø..........00000020 ....€.)....NO NA00000030 ME FAT16 ..00000040 ................00000050 ................
Oh, I figured out how to read the internal binaries of USB devices with certain software and FinaleTI used it to get a memory dump off of the Prizm.