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Index > Windows > HELP!! Manual Calculation of CRC32

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crc32



Joined: 17 Nov 2004
Posts: 5
crc32
Hi all,

I am stuck, I just want to make sure that my CRC32 values are correct. My perl script reads in a file. Currently my file is in Unicode format, and only contain a character "a". I want to do a CRC32 manual calculation on that

a = FF FE 61 00, which transfers to 11111111 11111110 01100001 00000000
for crc32, highest power is 32, so I add 32 zeros to my message

so message =
11111111 11111110 01100001 00000000 00000000 00000000 00000000 00000000

since its CRC32 (x^32+x^26+x^23+X^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+1) : i am using the following to divide:
poly: 100000100110000010001110110110111

I manually calculated on paper:
Result=10001010011010001000111000110111

the crc32 value from my perl script using String::CRC32 to open file in Unicode format
= 111100111111011101110111010001

I also tried the same file but in ASCII format
= 11101000101101111011111001000011

damn..both are incorrect....

I did the manual calculation twice.... and got the same answer....

where is my calculation wrong?
the message is only 'a' in a file, FF FE 61 00
is the message wrong to begin with?

thank you for your help in advance.

regards
Jim

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CRC32 Manual Calculation: HELP>>>> I am stuck
Post 17 Nov 2004, 01:56
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Matrix



Joined: 04 Sep 2004
Posts: 1171
Location: Overflow
Matrix
hope this helps ( its in assembly ) :


or check out this site

Although the MD5, SHA1, SHA256, SHA384, and SHA512 are more accurate than the CRC32 algorithm, sometimes you do not have a choice due various reasons. This class can be used without modification anywhere other HashAlgorithm classes can.

so you should try this search on gogle
Post 17 Nov 2004, 03:46
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crc32



Joined: 17 Nov 2004
Posts: 5
crc32
thanks for the website..
I can use the code no problem..

I am just having problem manually calculating the values...

let me know if you can manually calculate crc32 value of "a" in unicode...
FF FE 61 00

thanks..

Jim

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CRC32 Manual Calculation: HELP>>>> I am stuck
Post 17 Nov 2004, 19:42
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