| 1 | #!/usr/bin/python |
| 2 | |
| 3 | # xorcheck.py - find xor values for 8-bit LRC |
| 4 | # |
| 5 | # Adam Laurie <adam@algroup.co.uk> |
| 6 | # http://rfidiot.org/ |
| 7 | # |
| 8 | # This code is copyright (c) Adam Laurie, 2009, All rights reserved. |
| 9 | # For non-commercial use only, the following terms apply - for all other |
| 10 | # uses, please contact the author: |
| 11 | # |
| 12 | # This code is free software; you can redistribute it and/or modify |
| 13 | # it under the terms of the GNU General Public License as published by |
| 14 | # the Free Software Foundation; either version 2 of the License, or |
| 15 | # (at your option) any later version. |
| 16 | # |
| 17 | # This code is distributed in the hope that it will be useful, |
| 18 | # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | # GNU General Public License for more details. |
| 21 | # |
| 22 | |
| 23 | import sys |
| 24 | import os |
| 25 | |
| 26 | if(len(sys.argv) < 3): |
| 27 | print |
| 28 | print '\t'+sys.argv[0] + ' - Generate final byte for XOR LRC' |
| 29 | print |
| 30 | print 'Usage: ' + sys.argv[0] + ' <ID Byte1> <ID Byte2> ... <LRC>' |
| 31 | print |
| 32 | print '\tSpecifying the bytes of a UID with a known LRC will find the last byte value' |
| 33 | print '\tneeded to generate that LRC with a rolling XOR. All bytes should be specified in HEX.' |
| 34 | print |
| 35 | print 'Example:' |
| 36 | print |
| 37 | print '\txorcheck.py 04 00 80 64 ba' |
| 38 | print |
| 39 | print 'Should produce the output:' |
| 40 | print |
| 41 | print '\tTarget (BA) requires final LRC XOR byte value: 5A' |
| 42 | print |
| 43 | os._exit(True) |
| 44 | |
| 45 | target= int(sys.argv[len(sys.argv) - 1],16) |
| 46 | |
| 47 | lrc= 0x00 |
| 48 | for i in range(len(sys.argv) - 1): |
| 49 | lrc ^= int(sys.argv[i + 1],16) |
| 50 | print |
| 51 | print 'Target (%02X) requires final LRC XOR byte value: %02X' % (target,lrc) |
| 52 | print |