Reverse engineering CRC?

Gregory Ewing greg.ewing at canterbury.ac.nz
Thu Mar 11 22:40:33 CET 2010


Steve Howell wrote:

> Hi Greg.  I would at least flip one bit at a time on the first byte of
> your data to see if the transformation is bitwise.

I'm actually making good progress on this -- it turns out
there *is* a way of deducing the polynomial by looking at
the effect of single-bit flips. It's actually quite simple,
with no brute-force searching needed at all.

Things get a bit tricky when you don't quite know all
of the data that goes into the CRC, though, which seems
to be the case here...

I'm writing up an essay on my experiences. I'll post a
link when it's finished.

-- 
Greg



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