Reverse engineering CRC?

[Lawrence D'Oliveiro]

In message <7vlameF7goU1 at mid.individual.net>, Gregory Ewing wrote:

> I'm going by the fact that the application reports a
> "CRC mismatch" when it's wrong. I can't be sure that what
> it calls a "CRC" is really a true CRC, but it's more than
> a simple sum, because changing one bit in the file results
> in a completely different value.

They could be using a strong cryptographic hash and truncating it to 16 bits 
or something.

In which case you’ve got your work cut out for you...