RRG-Proxmark3/tools/mfc/card_reader/iso14443crc.c
2024-08-02 00:10:23 +02:00

46 lines
1.6 KiB
C

//-----------------------------------------------------------------------------
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// ISO14443 CRC calculation code.
//-----------------------------------------------------------------------------
#include "iso14443crc.h"
static unsigned short UpdateCrc14443(unsigned char ch, unsigned short *lpwCrc) {
ch = (ch ^ (unsigned char)((*lpwCrc) & 0x00FF));
ch = (ch ^ (ch << 4));
*lpwCrc = (*lpwCrc >> 8) ^ ((unsigned short) ch << 8) ^
((unsigned short) ch << 3) ^ ((unsigned short) ch >> 4);
return (*lpwCrc);
}
void ComputeCrc14443(int CrcType,
const unsigned char *Data, int Length,
unsigned char *TransmitFirst,
unsigned char *TransmitSecond) {
unsigned short wCrc = CrcType;
do {
unsigned char chBlock = *Data++;
UpdateCrc14443(chBlock, &wCrc);
} while (--Length);
if (CrcType == CRC_14443_B)
wCrc = ~wCrc; /* ISO/IEC 13239 (formerly ISO/IEC 3309) */
*TransmitFirst = (unsigned char)(wCrc & 0xFF);
*TransmitSecond = (unsigned char)((wCrc >> 8) & 0xFF);
return;
}
int CheckCrc14443(int CrcType, const unsigned char *Data, int Length) {
unsigned char b1;
unsigned char b2;
if (Length < 3) return 0;
ComputeCrc14443(CrcType, Data, Length - 2, &b1, &b2);
if ((b1 == Data[Length - 2]) && (b2 == Data[Length - 1])) return 1;
return 0;
}