proxmark3/common/iso15693tools.c

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//-----------------------------------------------------------------------------
// 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.
//-----------------------------------------------------------------------------
// ISO15693 CRC & other commons
//-----------------------------------------------------------------------------
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#include "../include/proxmark3.h"
#include <stdint.h>
#include <stdlib.h>
//#include "iso15693tools.h"
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#define POLY 0x8408
// The CRC as described in ISO 15693-Part 3-Annex C
// v buffer with data
// n length
// returns crc as 16bit value
uint16_t Iso15693Crc(uint8_t *v, int n)
{
uint32_t reg;
int i, j;
reg = 0xffff;
for(i = 0; i < n; i++) {
reg = reg ^ ((uint32_t)v[i]);
for (j = 0; j < 8; j++) {
if (reg & 0x0001) {
reg = (reg >> 1) ^ 0x8408;
} else {
reg = (reg >> 1);
}
}
}
return ~(uint16_t)(reg & 0xffff);
}
// adds a CRC to a dataframe
// req[] iso15963 frame without crc
// n length without crc
// returns the new length of the dataframe.
int Iso15693AddCrc(uint8_t *req, int n) {
uint16_t crc=Iso15693Crc(req,n);
req[n] = crc & 0xff;
req[n+1] = crc >> 8;
return n+2;
}
int sprintf(char *str, const char *format, ...);
// returns a string representation of the UID
// UID is transmitted and stored LSB first, displayed MSB first
// target char* buffer, where to put the UID, if NULL a static buffer is returned
// uid[] the UID in transmission order
// return: ptr to string
char* Iso15693sprintUID(char *target,uint8_t *uid) {
static char tempbuf[2*8+1]="";
if (target==NULL) target=tempbuf;
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sprintf(target,"%02X%02X%02X%02X%02X%02X%02X%02X",
uid[7],uid[6],uid[5],uid[4],uid[3],uid[2],uid[1],uid[0]);
return target;
}
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uint16_t iclass_crc16(char *data_p, unsigned short length)
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{
unsigned char i;
unsigned int data;
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uint16_t crc = 0xffff;
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if (length == 0)
return (~crc);
do
{
for (i=0, data=(unsigned int)0xff & *data_p++;
i < 8;
i++, data >>= 1)
{
if ((crc & 0x0001) ^ (data & 0x0001))
crc = (crc >> 1) ^ POLY;
else crc >>= 1;
}
} while (--length);
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crc = ~crc;
data = crc;
crc = (crc << 8) | (data >> 8 & 0xff);
crc = crc ^ 0xBC3;
return (crc);
}