I tried doing some trial and error experimentation with my code and
CRC calculation
using a string with 6 characters, reversing or not the results and bit by bit computations
If is usefull I can post the source for my function.
Googled 'cksum source code' and saw about some 30 different links take where mainly to forum threads asking for the same thing and an old sum BSD code.
I also read it there should be somewhere in my linux dist (fedora 10) but I don't know where (package it comes in).