CRC

This software is used to check the integrity of installer archives downloaded from the Alchemy Mindworks web page.

CRC is freeware.
The CRC program calculates a "cyclical redundancy check" value for the files you specify. In effect, it performs a complex calculation on every byte in the file, generating a unique number for the file in question. If so much as a single byte in the file being checked were to change, the cyclical redundancy check value for that file would also change.