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[proxmark3-svn] / tools / xorcheck.py
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
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