Need help about CRC calculation. 
Author Message
 Need help about CRC calculation.

Hello, please help me to solve this problem:
How do we find 4 bytes to append to the end of a bit stream so that
the CRC32 calculation on the new bit steam always produce a constant
value no matter what the bit stream is. This constant value is not
zero.

Normally, the 4 bytes are just the CRC of the original bit stream ,and
when we run the CRC checker to the (bit stream+4 byte CRC), it will
produce a zero.

So far, I did not find anyone discuss this. But I do find a person
post a similar question on 4/12/2002 on a web site and no noe offers
an answer yet.


Thanks in advance.

Z. Fan



Sun, 17 Oct 2004 20:39:54 GMT  
 Need help about CRC calculation.
Here's an algorithm I've been using for years. Input is stepped by byte. If
you want the code, reply to the newsgroup...

*
*        ACC = 0XFFFFFFFF
* LOOP:  ACC = ACC XOR INPUT
*        ACC = ACC < 1
*        IF CARRY, ACC = ACC XOR 0X1D1D1D1D
*        GOTO LOOP
*



Quote:
> Hello, please help me to solve this problem:
> How do we find 4 bytes to append to the end of a bit stream so that
> the CRC32 calculation on the new bit steam always produce a constant
> value no matter what the bit stream is. This constant value is not
> zero.

> Normally, the 4 bytes are just the CRC of the original bit stream ,and
> when we run the CRC checker to the (bit stream+4 byte CRC), it will
> produce a zero.

> So far, I did not find anyone discuss this. But I do find a person
> post a similar question on 4/12/2002 on a web site and no noe offers
> an answer yet.


> Thanks in advance.

> Z. Fan



Tue, 26 Oct 2004 08:30:51 GMT  
 
 [ 2 post ] 

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