common/iso15693tools.c

   1 //-----------------------------------------------------------------------------
   2 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
   3 // at your option, any later version. See the LICENSE.txt file for the text of
   4 // the license.
   5 //-----------------------------------------------------------------------------
   6 // ISO15693 CRC & other commons
   7 //-----------------------------------------------------------------------------
   8
   9
  10 #include "proxmark3.h"
  11 #include <stdint.h>
  12 #include <stdlib.h>
  13 //#include "iso15693tools.h"
  14
  15 #define POLY 0x8408
  16
  17
  18 // The CRC as described in ISO 15693-Part 3-Annex C
  19 //      v       buffer with data
  20 //              n       length
  21 //      returns crc as 16bit value
  22 uint16_t Iso15693Crc(uint8_t *v, int n)
  23 {
  24         uint32_t reg;
  25         int i, j;
  26
  27         reg = 0xffff;
  28         for(i = 0; i < n; i++) {
  29                 reg = reg ^ ((uint32_t)v[i]);
  30                 for (j = 0; j < 8; j++) {
  31                         if (reg & 0x0001) {
  32                                 reg = (reg >> 1) ^ 0x8408;
  33                         } else {
  34                                 reg = (reg >> 1);
  35                         }
  36                 }
  37         }
  38
  39         return ~(uint16_t)(reg & 0xffff);
  40 }
  41
  42 // adds a CRC to a dataframe
  43 //      req[]   iso15963 frame without crc
  44 //              n       length without crc
  45 // returns the new length of the dataframe.
  46 int Iso15693AddCrc(uint8_t *req, int n) {
  47         uint16_t crc=Iso15693Crc(req,n);
  48         req[n] = crc & 0xff;
  49         req[n+1] = crc >> 8;
  50         return n+2;
  51 }
  52
  53
  54 int sprintf(char *str, const char *format, ...);
  55
  56 // returns a string representation of the UID
  57 // UID is transmitted and stored LSB first, displayed MSB first
  58 //              target    char* buffer, where to put the UID, if NULL a static buffer is returned
  59 //              uid[]           the UID in transmission order
  60 //      return: ptr to string
  61 char* Iso15693sprintUID(char *target,uint8_t *uid) {
  62   static char tempbuf[2*8+1]="";
  63   if (target==NULL) target=tempbuf;
  64   sprintf(target,"%02X%02X%02X%02X%02X%02X%02X%02X",
  65                                 uid[7],uid[6],uid[5],uid[4],uid[3],uid[2],uid[1],uid[0]);
  66   return target;
  67 }
  68
  69 uint16_t iclass_crc16(char *data_p, unsigned short length)
  70 {
  71       unsigned char i;
  72       unsigned int data;
  73           uint16_t crc = 0xffff;
  74
  75       if (length == 0)
  76             return (~crc);
  77
  78       do
  79       {
  80             for (i=0, data=(unsigned int)0xff & *data_p++;
  81                  i < 8;
  82                  i++, data >>= 1)
  83             {
  84                   if ((crc & 0x0001) ^ (data & 0x0001))
  85                         crc = (crc >> 1) ^ POLY;
  86                   else  crc >>= 1;
  87             }
  88       } while (--length);
  89
  90       crc = ~crc;
  91       data = crc;
  92       crc = (crc << 8) | (data >> 8 & 0xff);
  93       crc = crc ^ 0xBC3;
  94       return (crc);
  95 }
  96