proxmark3/tools/xorcheck.py

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#!/usr/bin/python
# xorcheck.py - find xor values for 8-bit LRC
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#
# Adam Laurie <adam@algroup.co.uk>
# http://rfidiot.org/
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#
# This code is copyright (c) Adam Laurie, 2009, All rights reserved.
# For non-commercial use only, the following terms apply - for all other
# uses, please contact the author:
#
# This code is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This code is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
import sys
import os
if(len(sys.argv) < 3):
print
print '\t'+sys.argv[0] + ' - Generate final byte for XOR LRC'
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print
print 'Usage: ' + sys.argv[0] + ' <ID Byte1> <ID Byte2> ... <LRC>'
print
print '\tSpecifying the bytes of a UID with a known LRC will find the last byte value'
print '\tneeded to generate that LRC with a rolling XOR. All bytes should be specified in HEX.'
print
print 'Example:'
print
print '\txorcheck.py 04 00 80 64 ba'
print
print 'Should produce the output:'
print
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print '\tTarget (BA) requires final LRC XOR byte value: 5A'
print
os._exit(True)
target= int(sys.argv[len(sys.argv) - 1],16)
lrc= 0x00
for i in range(len(sys.argv) - 1):
lrc ^= int(sys.argv[i + 1],16)
print
print 'Target (%02X) requires final LRC XOR byte value: %02X' % (target,lrc)
print