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CRC32Digest produces differing values


From: M. Wied
Subject: CRC32Digest produces differing values
Date: Tue, 10 May 2005 10:37:30 -0000
User-agent: KMail/1.7.2

Hello everybody.
I've been using cc++ libraries without being aware of bugs for several 
versions now, but needed the CRC32 computation recently. 
Unfortuantely I got constantly values that differed form those of the other 
project memebers. When investigating, I found in your corresponding source 
file that an ethernet compliant CRC32-polynom was used. 
I found a specification at 
http://www.geocities.com/SiliconValley/Pines/8659/crc.htm by  Ross N. 
Williams
that stated values, that all other members of our group could reproduce, but 
not cc++ : 
--------------->
Here is the specification for the CRC-32 algorithm which is reportedly       
used in PKZip, AUTODIN II, Ethernet, and FDDI.                               
                                                                             
   Name   : "CRC-32"                                                         
   Width  : 32                                                               
   Poly   : 04C11DB7                                                         
   Init   : FFFFFFFF                                                         
   RefIn  : True                                                             
   RefOut : True                                                             
   XorOut : FFFFFFFF                                                         
   Check  : CBF43926 
-----------------<      

Check means Checksum when digesting "123456789"
Though the specification states that this would be ethernet too, it differs 
from cc++ results. I could reproduce the results of the expamle (AAL-5 - ATM) 
with cc++ but the perl, java and other c implementations get different values 
for these checks even though the poly you is the same as the one mentioned 
above.
Any idea what the reason might be?

Thanx,
Markus
-- 
 _____   _            _    _      __  ____   _ ______ _______  
(____ \ (_)          | |  / )    /  |/ __ \ | / __   (_______) 
 _   \ \ _  ____     | | / /_ _ /_/ ( (__) ) / | //| |______   
| |   | | |/ _  )    | |< <| | | || |\__  / /| |// | (_____ \  
| |__/ /| ( (/ / _   | | \ \ | | || |  / / / |  /__| |_____) ) 
|_____/ |_|\____| )  |_|  \_)____||_| /_/_|   \_____/(______( )
                |/                                          |/ 
 ______        _       __ ______     ______  _____    ______  ____  
|  ___ \      (_)     /  (_____ \   / __   |/ ___ \  / __   |/ __ \ 
| | _ | | ____ _     /_/ | ____) )_| | //| ( (   ) )| | //| ( (__) )
| || || |/ _  | |      | |/_____/(_) |// | |> > < <_) |// | |\__  / 
| || || ( ( | | |_     | |_______ _|  /__| ( (___) )|  /__| |  / /  
|_||_||_|\_||_|_( )    |_(_______|_)\_____/ \_____(_)\_____/  /_/   
                |/                                                  
  ______ _______    _    _______ 
 / _____|_______)  | |  (_______)
| /      _____      \ \  _       
| |     |  ___)      \ \| |      
| \_____| |_____ _____) ) |_____ 
 \______)_______|______/ \______)
                                 

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