Mifare Ultralight C : Authentication key is not unique !!

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What steps will reproduce the problem?
1. Get a Mifare Ultralight C with default key "BREAKMEIFYOUCAN!"
2. Compile & run the attached libfreefare code (based on your 
example/mifare-ultralight-info.c)
3. You can see multiple keys working for authentication

What is the expected output? 
Everything fails except the valid key

What do you see instead?
Trying G as first letterAuthentication with key: fail
Trying H as first letterAuthentication with key: success
Trying I as first letterAuthentication with key: success

What version of the product are you using? On what operating system?
libnfc-1.6.0-rc1
libfreefare-0.3.4
Linux debian 3.0.52+ #3 PREEMPT Fri Jan 4 03:14:20 CET 2013 armv7l GNU/Linux

Please provide any additional information below.
Chip : PN532 UART via FTDI

Original issue reported on code.google.com by thomas.d...@gmail.com on 4 Jan 2013 at 6:05

Attachments:

• mifare-ultralight-info.c

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Original comment by romu...@libnfc.org on 20 Jan 2013 at 4:17

• Added labels: Component-libfreefare

[GoogleCodeExporter]

Hello,

Thanks for reporting but libfreefare is not hosted here anymore...

Please use the appropriated issue tracker:
https://code.google.com/p/libfreefare/issues/list

( and feel free to provide a patch ;-) )

Original comment by romu...@libnfc.org on 4 Apr 2013 at 10:08

• Changed state: Invalid

[GoogleCodeExporter]

Those are 3DES keys, it's normal that several keys work.
3DES key is a 112bit key written in 16 bytes = 128bit
If you change those 16 "parity bits" the key is still valid.

Original comment by yob...@gmail.com on 4 Apr 2013 at 11:41