An arbitrary-precision CRC calculator and algorithm finder
http://reveng.sourceforge.net/

CRC RevEng is a portable, arbitrary-precision CRC calculator and
algorithm finder. It calculates CRCs using any of the 72 preset
algorithms, or a user-specified algorithm to any width. It calculates
reversed CRCs to give the bit pattern that produces a desired forward
CRC. CRC RevEng also reverse-engineers any CRC algorithm from
sufficient correctly formatted message-CRC pairs and optional known
parameters. It comprises powerful input interpretation options.
Compliant with Ross Williams' Rocksoft(tm) model of parametrised CRC
algorithms.