[Icc-avr] CheckSum
Jaspers, Ton
t.jaspers at cpseurope.com
Tue May 27 00:18:02 PDT 2008
Steven forgets to mention which polinomal is used. I guess its CCITT-CRC16 but I could be wrong.
There are so many hash calculations out there, it would help to identify the polinomal used.
Here is a CCITT-CRC8 calculator/checker and another goodie, a 160 bit SHA1:
/*----------------------------------------------*/
uchar crc8( uchar *src, uchar len )
{
uchar x, j, k, crc ;
crc = 0 ;
while ( len-- )
{
x = *src++ ;
for ( k = 0; k < 8; k++ )
{
j = (x ^ crc) & 1 ;
crc >>= 1 ;
x >>= 1 ;
if ( j )
{
crc ^= 0x8C ;
}
}
}
return ( crc ) ;
}
-------------------------------------------------
/*
* sha1.c
*
* Copyright (C) 1998
* Paul E. Jones <paulej at arid.us>
* All Rights Reserved
*
*****************************************************************************
* $Id: sha1.c,v 1.2 2004/03/27 18:00:33 paulej Exp $
*****************************************************************************
*
* Description:
* This file implements the Secure Hashing Standard as defined
* in FIPS PUB 180-1 published April 17, 1995.
*
* The Secure Hashing Standard, which uses the Secure Hashing
* Algorithm (SHA), produces a 160-bit message digest for a
* given data stream. In theory, it is highly improbable that
* two messages will produce the same message digest. Therefore,
* this algorithm can serve as a means of providing a "fingerprint"
* for a message.
*
* Portability Issues:
* SHA-1 is defined in terms of 32-bit "words". This code was
* written with the expectation that the processor has at least
* a 32-bit machine word size. If the machine word size is larger,
* the code should still function properly. One caveat to that
* is that the input functions taking characters and character
* arrays assume that only 8 bits of information are stored in each
* character.
*
* Caveats:
* SHA-1 is designed to work with messages less than 2^64 bits
* long. Although SHA-1 allows a message digest to be generated for
* messages of any number of bits less than 2^64, this
* implementation only works with messages with a length that is a
* multiple of the size of an 8-bit character.
*
*/
#include "sha1.h"
/*
* Define the circular shift macro
*/
#define SHA1CircularShift(bits,word) \
((((word) << (bits)) & 0xFFFFFFFF) | \
((word) >> (32-(bits))))
/* Function prototypes */
void SHA1ProcessMessageBlock(SHA1Context *);
void SHA1PadMessage(SHA1Context *);
/*
* SHA1Reset
*
* Description:
* This function will initialize the SHA1Context in preparation
* for computing a new message digest.
*
* Parameters:
* context: [in/out]
* The context to reset.
*
* Returns:
* Nothing.
*
* Comments:
*
*/
void SHA1Reset(SHA1Context *context)
{
context->Length_Low = 0;
context->Length_High = 0;
context->Message_Block_Index = 0;
context->Message_Digest[0] = 0x67452301;
context->Message_Digest[1] = 0xEFCDAB89;
context->Message_Digest[2] = 0x98BADCFE;
context->Message_Digest[3] = 0x10325476;
context->Message_Digest[4] = 0xC3D2E1F0;
context->Computed = 0;
context->Corrupted = 0;
}
/*
* SHA1Result
*
* Description:
* This function will return the 160-bit message digest into the
* Message_Digest array within the SHA1Context provided
*
* Parameters:
* context: [in/out]
* The context to use to calculate the SHA-1 hash.
*
* Returns:
* 1 if successful, 0 if it failed.
*
* Comments:
*
*/
int SHA1Result(SHA1Context *context)
{
if (context->Corrupted)
{
return 0;
}
if (!context->Computed)
{
SHA1PadMessage(context);
context->Computed = 1;
}
return 1;
}
/*
* SHA1Input
*
* Description:
* This function accepts an array of octets as the next portion of
* the message.
*
* Parameters:
* context: [in/out]
* The SHA-1 context to update
* message_array: [in]
* An array of characters representing the next portion of the
* message.
* length: [in]
* The length of the message in message_array
*
* Returns:
* Nothing.
*
* Comments:
*
*/
void SHA1Input( SHA1Context *context,
const unsigned char *message_array,
unsigned length)
{
if (!length)
{
return;
}
if (context->Computed || context->Corrupted)
{
context->Corrupted = 1;
return;
}
while(length-- && !context->Corrupted)
{
context->Message_Block[context->Message_Block_Index++] =
(*message_array & 0xFF);
context->Length_Low += 8;
/* Force it to 32 bits */
context->Length_Low &= 0xFFFFFFFF;
if (context->Length_Low == 0)
{
context->Length_High++;
/* Force it to 32 bits */
context->Length_High &= 0xFFFFFFFF;
if (context->Length_High == 0)
{
/* Message is too long */
context->Corrupted = 1;
}
}
if (context->Message_Block_Index == 64)
{
SHA1ProcessMessageBlock(context);
}
message_array++;
}
}
/*
* SHA1ProcessMessageBlock
*
* Description:
* This function will process the next 512 bits of the message
* stored in the Message_Block array.
*
* Parameters:
* None.
*
* Returns:
* Nothing.
*
* Comments:
* Many of the variable names in the SHAContext, especially the
* single character names, were used because those were the names
* used in the publication.
*
*
*/
void SHA1ProcessMessageBlock(SHA1Context *context)
{
const unsigned K[] = /* Constants defined in SHA-1 */
{
0x5A827999,
0x6ED9EBA1,
0x8F1BBCDC,
0xCA62C1D6
};
int t; /* Loop counter */
unsigned temp; /* Temporary word value */
unsigned W[80]; /* Word sequence */
unsigned A, B, C, D, E; /* Word buffers */
/*
* Initialize the first 16 words in the array W
*/
for(t = 0; t < 16; t++)
{
W[t] = ((unsigned) context->Message_Block[t * 4]) << 24;
W[t] |= ((unsigned) context->Message_Block[t * 4 + 1]) << 16;
W[t] |= ((unsigned) context->Message_Block[t * 4 + 2]) << 8;
W[t] |= ((unsigned) context->Message_Block[t * 4 + 3]);
}
for(t = 16; t < 80; t++)
{
W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
}
A = context->Message_Digest[0];
B = context->Message_Digest[1];
C = context->Message_Digest[2];
D = context->Message_Digest[3];
E = context->Message_Digest[4];
for(t = 0; t < 20; t++)
{
temp = SHA1CircularShift(5,A) +
((B & C) | ((~B) & D)) + E + W[t] + K[0];
temp &= 0xFFFFFFFF;
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 20; t < 40; t++)
{
temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
temp &= 0xFFFFFFFF;
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 40; t < 60; t++)
{
temp = SHA1CircularShift(5,A) +
((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
temp &= 0xFFFFFFFF;
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
for(t = 60; t < 80; t++)
{
temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
temp &= 0xFFFFFFFF;
E = D;
D = C;
C = SHA1CircularShift(30,B);
B = A;
A = temp;
}
context->Message_Digest[0] =
(context->Message_Digest[0] + A) & 0xFFFFFFFF;
context->Message_Digest[1] =
(context->Message_Digest[1] + B) & 0xFFFFFFFF;
context->Message_Digest[2] =
(context->Message_Digest[2] + C) & 0xFFFFFFFF;
context->Message_Digest[3] =
(context->Message_Digest[3] + D) & 0xFFFFFFFF;
context->Message_Digest[4] =
(context->Message_Digest[4] + E) & 0xFFFFFFFF;
context->Message_Block_Index = 0;
}
/*
* SHA1PadMessage
*
* Description:
* According to the standard, the message must be padded to an even
* 512 bits. The first padding bit must be a '1'. The last 64
* bits represent the length of the original message. All bits in
* between should be 0. This function will pad the message
* according to those rules by filling the Message_Block array
* accordingly. It will also call SHA1ProcessMessageBlock()
* appropriately. When it returns, it can be assumed that the
* message digest has been computed.
*
* Parameters:
* context: [in/out]
* The context to pad
*
* Returns:
* Nothing.
*
* Comments:
*
*/
void SHA1PadMessage(SHA1Context *context)
{
/*
* Check to see if the current message block is too small to hold
* the initial padding bits and length. If so, we will pad the
* block, process it, and then continue padding into a second
* block.
*/
if (context->Message_Block_Index > 55)
{
context->Message_Block[context->Message_Block_Index++] = 0x80;
while(context->Message_Block_Index < 64)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
SHA1ProcessMessageBlock(context);
while(context->Message_Block_Index < 56)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
}
else
{
context->Message_Block[context->Message_Block_Index++] = 0x80;
while(context->Message_Block_Index < 56)
{
context->Message_Block[context->Message_Block_Index++] = 0;
}
}
/*
* Store the message length as the last 8 octets
*/
context->Message_Block[56] = (context->Length_High >> 24) & 0xFF;
context->Message_Block[57] = (context->Length_High >> 16) & 0xFF;
context->Message_Block[58] = (context->Length_High >> 8) & 0xFF;
context->Message_Block[59] = (context->Length_High) & 0xFF;
context->Message_Block[60] = (context->Length_Low >> 24) & 0xFF;
context->Message_Block[61] = (context->Length_Low >> 16) & 0xFF;
context->Message_Block[62] = (context->Length_Low >> 8) & 0xFF;
context->Message_Block[63] = (context->Length_Low) & 0xFF;
SHA1ProcessMessageBlock(context);
}
________________________________
From: icc-avr-bounces at imagecraft.com [mailto:icc-avr-bounces at imagecraft.com] On Behalf Of Steven Lose
Sent: dinsdag 27 mei 2008 8:20
To: Discussion list for ICCAVR and ICCtiny Users. You do NOT need tosubscribeto icc-announce if you are a member of this.
Subject: SV: [Icc-avr] CheckSum
Hi Albert.
I got this CRC from John Baraclough (If I remenbor wrong then sorry to the one I forgot)
Thanks anyway, works fine, I use it on all serial communication.
unsigned int CalcCrc(unsigned char *Packet,unsigned char NumberOfBytes)
{
#define POLYNOMIAL (unsigned int)0xa001
unsigned char ucByteCount,ucBitCount;
unsigned int uiCRC;
uiCRC = 0xFFFF;
for(ucByteCount=0;ucByteCount<NumberOfBytes;ucByteCount++)
{
uiCRC ^= (unsigned int)(*Packet++);
for(ucBitCount=0;ucBitCount<8;ucBitCount++)
{
if(uiCRC & 0x0001)
{
uiCRC >>= 1;
uiCRC ^= POLYNOMIAL;
}
else
uiCRC >>= 1;
}
}
return uiCRC;
}
Med venlig hilsen / Best regards / mit freundlichen Grüßen
EC POWER A/S
Steven Lose
Software Ingeniør
Tlf.: +45 87434100
Direkte tlf. +45 58286608
Email: sl at ecpower.dk <blocked::mailto:bsl at ecpower.dk>
www.ecpower.dk
________________________________
Fra: icc-avr-bounces at imagecraft.com [mailto:icc-avr-bounces at imagecraft.com] På vegne af Albert vanVeen
Sendt: 27. maj 2008 00:37
Til: Discussion list for ICCAVR and ICCtiny Users. You do NOT needtosubscribeto icc-announce if you are a member of this.
Emne: RE: [Icc-avr] CheckSum
It would indeed be a good idea to add a checksum to comms functions!
Depends what you want: plain CS, CRC, Fletcher?
We've used FCS in the companies I've worked the last 20 or so years, seems to be accepted as "the best" value for 16 bits.
Albert.
________________________________
From: icc-avr-bounces at imagecraft.com [mailto:icc-avr-bounces at imagecraft.com] On Behalf Of Andrew
Sent: Tuesday, May 27, 2008 09:25 AM
To: Discussion list for ICCAVR and ICCtiny Users. You do NOT needtosubscribeto icc-announce if you are a member of this.
Subject: [Icc-avr] CheckSum
Hi,
I am sure I have asked this before but (if i have sorry for the repeat question), does anybody have a simple checksum routine for an array of bytes, they would not mind posting?
I need one for a maximum of 250 bytes I am sending through the serial port to a PC (I could break this up into smaller chunks if needed ) at the moment i am not using one, but I think it would be best to add one.
I have found a few on AVR freaks, just wondered what everyone here uses.
Best Regards,
Andy
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