Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!munnari.oz.au!murtoa.cs.mu.oz.au!rob
From: rob@cs.mu.oz.au (Robert Wallen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: crc functions
Keywords: ccitt
Message-ID: <2981@murtoa.cs.mu.oz.au>
Date: 9 Mar 90 23:48:31 GMT
References: <8548@netcom.UUCP> <1990Mar7.065639.11927@Neon.Stanford.EDU>
Reply-To: rob@murtoa.UUCP (Robert Wallen)
Organization: Comp Sci, Melbourne Uni, Australia
Lines: 19

In article <1990Mar7.065639.11927@Neon.Stanford.EDU> kaufman@Neon.Stanford.EDU (Marc T. Kaufman) writes:
>
>The way CRCs are meant to be used is:  Initialize the CRC to all 1's, then
>compute the CRC of the message.  Send the message with the CRC appended to it.
>On the receiving side, initialize the CRC to all 0's.  Compute the CRC of the
>entire message PLUS the message CRC.  The result should be 0.  If not, you

Can someone confirm this?  Or preferably deny it?  I have never used a seed
value of all 1's (except one weirdo case where it wasnt CCITT CRC's being 
used anyway)

From my (limited) understanding of the underlying mathematics (polynomial
division), it doesnt make a lot of sense to start with different values at
the sender and the receiver ...

Ohh, did anybody think to crosspost this to comp.os.minix?  It would be 
interesting to see what ast@whereever.he.is had to say; as I recall, 
'Computer Networks' was the first book that ever really explained these things
good enough for me to just accept that 'yeh, they work'