CRC checksums

[Nigel Major]

I am posting this for a friend who has no net access.

She is trying to reverse engineer the data format of various CAD systems
in order to write database conversion software.  In order to check for
file corruption, some formats use error correction checks similar to those
used when passing files around a network.  She needs to generate the
checksums produced by these corruption checks in order to write valid
files.

So she is looking for information about established methods of working out
how these checksums are produced - either numerical methods or commercial
software.  She is particularly interested in methods of calculating
polynomials used in generating Cyclic Redundancy Check checksums -
especially CRC-32 type checks.

If anybody could point to some information about this, we would be very
grateful.

Cheers, Nigel