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 Forums >>  Debuggers  >>  Ollydbg & CRC Alo Finding Help

Topic created on: December 10, 2008 05:09 CST by Xerosigma .

Hi readers, I'm very new to the scene forgive me if I give you hell.

Well I'm trying to find a CRC alogorithm in some memory and I'm not sure how exactly to go about searching for it. I know the .bin file the CRC is checking for the memory but I'm not sure if or how to use this to help me find the CRC. I think I can also guess which memory region the CRC is checking. I have such little information I hope someone can lead me in the right direction. Thank you.

  nezumi     December 10, 2008 07:28.32 CST
just set a hardware access breakpoint on any byte belongs to the checked region and see the code that performs checks. it works well, however, protections can map the memory block to another region, so, your breakpoint will not be triggered.

also some CRC algorithms use well-known constant (for example, 0x04C11dB7 for CRC-32 according to IEEE 802.3), but it's easy to obfuscate them, so, plain search will give nothing.

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