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#1 2013-08-27 20:54:44

midnitesnake
Contributor
Registered: 2012-05-11
Posts: 151

LF 125kHz Traces & Wiki Walkthrough [Solved]

Im trying to follow the LF example on the wiki but I'm getting different data back, is the wiki incorrect or is the code broken within the client? Im using Revision 757

proxmark3> data load traces/EM4102-1.pm3 
loaded 16000 samples      
proxmark3> data plot    
proxmark3> data askdemod 1
proxmark3> data mandemod 64
Warning: Manchester decode error for pulse width detection.          
(too many of those messages mean either the stream is not Manchester encoded, or clock is wrong)          
Unsynchronized, resync...          
(too many of those messages mean the stream is not Manchester encoded)          
Manchester decoded bitstream          
0 0 1 0 1 1 1 1 0 1 0 1 1 1 1 0          
1 1 1 1 1 1 0 0 0 1 1 1 0 0 1 1          
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1          
1 0 0 0 0 0 1 0 0 0 1 0 1 1 1 1          
0 0 1 0 1 1 1 1 0 1 0 1 1 1 1 0          
1 1 1 1 1 1 0 0 0 1 1 1 0 0 1 1          
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1          
1 0 0 0 0 0 1 0 0 0 1 0 1 1 1 1          
0 0 1 0 1 1 1 1 0 1 0 1 1 1 1 0          
1 1 1 1 1 1 0 0 0 1 1 1 0 0 1 1          
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1          
1 0 0 0 0 0 1 0 0 0 1 0 1 1 1 1          
0 0 1 0 1 1 1 1 0 1 0 1 1 1 1 0          
1 1 1 1 1 1 0 0 0 1 1 1 0 0 1 1          
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1  

I see this pattern:

1 1 1 1 1 1 1 1 1
0 0 0 0 |0 |0 0 0 1| 1| 0 0 0 0| 0| 1 0 0 0| 1| 0 1 1 1| 1| 0 0 1 0| 1| 1 1 1 0| 1| 0 1 1 1 |1| 0 1 1 1| 1| 1 1 0 0| 0| 1 1 1 0| 0
0x010872E77C

Any insight would be helpful. Especially, if Ive gone wrong?

Thanks

Last edited by midnitesnake (2013-09-04 19:52:59)

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#2 2013-08-31 11:29:57

adam@algroup.co.uk
Contributor
From: UK
Registered: 2009-05-01
Posts: 203
Website

Re: LF 125kHz Traces & Wiki Walkthrough [Solved]

Don't do the ASKDEMOD step:

proxmark3> data load traces/EM4102-1.pm3
loaded 16000 samples         
proxmark3> data mandemod
Manchester decoded bitstream         
1 0 0 0 0 0 0 1 1 1 0 0 0 1 1 0         
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1         
0 0 1 1 1 1 1 0 1 1 1 0 1 0 0 0         
0 1 1 0 1 0 0 0 0 1 0 1 0 0 0 0         
1 0 0 0 0 0 0 1 1 1 0 0 0 1 1 0         
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1         
0 0 1 1 1 1 1 0 1 1 1 0 1 0 0 0         
0 1 1 0 1 0 0 0 0 1 0 1 0 0 0 0         
1 0 0 0 0 0 0 1 1 1 0 0 0 1 1 0         
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1

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#3 2013-08-31 19:50:29

midnitesnake
Contributor
Registered: 2012-05-11
Posts: 151

Re: LF 125kHz Traces & Wiki Walkthrough [Solved]

Still get 0x10872E77C with your trace, I guess the proxmark client and my methodology are right, and the wiki is wrong.

It appears the "askdemod 1" just inverts the bits (as per EM4100 protocol).

PS. Also used http://andrewmohawk.com/EM41X/# to check the bitstream

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