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
  10 #include "iso15693tools.h"
  11
  12 #include "proxmark3.h"
  13 #include <stdint.h>
  14 #include <stdlib.h>
  15 #ifdef ON_DEVICE
  16 #include "printf.h"
  17 #else
  18 #include <stdio.h>
  19 #endif
  20
  21
  22 #define ISO15693_CRC_PRESET  (uint16_t)0xFFFF
  23 #define ISO15693_CRC_POLY    (uint16_t)0x8408
  24
  25
  26 // The CRC as described in ISO 15693-Part 3-Annex C
  27 //    v   buffer with data
  28 //    n   length
  29 //  returns crc as 16bit value
  30 uint16_t Iso15693Crc(uint8_t *v, int n) {
  31         uint32_t reg;
  32         int i, j;
  33
  34         reg = ISO15693_CRC_PRESET;
  35         for (i = 0; i < n; i++) {
  36                 reg = reg ^ ((uint32_t)v[i]);
  37                 for (j = 0; j < 8; j++) {
  38                         if (reg & 0x0001) {
  39                                 reg = (reg >> 1) ^ ISO15693_CRC_POLY;
  40                         } else {
  41                                 reg = (reg >> 1);
  42                         }
  43                 }
  44         }
  45
  46         return ~(uint16_t)(reg & 0xffff);
  47 }
  48
  49 // adds a CRC to a dataframe
  50 //    req[]   iso15963 frame without crc
  51 //    n       length without crc
  52 // returns the new length of the dataframe.
  53 int Iso15693AddCrc(uint8_t *req, int n) {
  54         uint16_t crc = Iso15693Crc(req, n);
  55         req[n] = crc & 0xff;
  56         req[n+1] = crc >> 8;
  57         return n + 2;
  58 }
  59
  60
  61 // returns a string representation of the UID
  62 // UID is transmitted and stored LSB first, displayed MSB first
  63 //    target    char* buffer, where to put the UID, if NULL a static buffer is returned
  64 //    uid[]     the UID in transmission order
  65 //    return:   ptr to string
  66 char* Iso15693sprintUID(char *target, uint8_t *uid) {
  67         static char tempbuf[2*8+1] = "";
  68         if (target == NULL) target = tempbuf;
  69         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]);
  70         return target;
  71 }
  72
  73
  74 uint16_t iclass_crc16(char *data_p, unsigned short length) {
  75         unsigned char i;
  76         unsigned int data;
  77         uint16_t crc = ISO15693_CRC_PRESET;
  78
  79         if (length == 0)
  80                 return (~crc);
  81
  82         do {
  83                 for (i = 0, data = (unsigned int)0xff & *data_p++; i < 8; i++, data >>= 1) {
  84                         if ((crc & 0x0001) ^ (data & 0x0001))
  85                                 crc = (crc >> 1) ^ ISO15693_CRC_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