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