CRC hacking on steroids

So... CRC32 is not secure to begin with, that's obvious. I'm looking to modify a file so it matches a certain CRC. This is very easy by changing/appending bytes at the very end of the file, a naive algorithm takes a few seconds.

But what I'm looking for is the ability to set the CRC changing a few bytes at some arbitrary offset in the file. Bruteforcing is out of the way since there are hundreds of megabytes after the desired offset.

Anyone up for the challenge? If I knew shit about CRCs, I'd say this would be easy as fuck.

If I knew shit about CRCs, I'd say this would be easy as fuck.
I guess that's the problem then isn't it? You don't know shit about CRCs, and it's most certainly not.

If I knew shit about CRCs, I'd say this would be easy as fuck.

Read SICP

just implement CRC in Prolog like crc(Data,Checksum) :- ... and then use it in a query with the Checksum set to the checksum you need and the Data with uninstantiated variables at the offsets, Prolog works by unification and search so it will be able to run the crc/2 backwards and fill in the bytes just like you need. good luck!

Jesus Fucking Christ, modern search engines suck so much. Searching for this made me realize how we're still in the stone age of search.

It's either you hit the very exact term or you're completely fucked. Also the relevancy of results works as bad as public moderation (which is what it is).

Anyway, http://sar.informatik.hu-berlin.de/research/publications/SAR-PR-2006-05/SAR-PR-2006-05_.pdf and maybe http://noa.resare.com/2008/08/crc-32-reversal/ (it's unclear if this one can set it to some arbitrary CRC, but apparently it's useful to change data without changing CRC)