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#1 2015-01-16 13:21:12

J4CK
Member
Registered: 2015-01-09
Posts: 3

Read multiple Tags

Hi everyone,

I'm student from Germany writing my master thesis and I'm pretty new in RFID business. I got a Proxmark3 and a pile of work updating it to v1.1.0-115.

I'm able to read single tags but what I'm aiming for is to identify multiple tags in the readers field. So there are some collision issues. I tested it with Mifare Desfire EV1 cards but the Proxmark only reports, that there are multiple tags and there is a collision. As far as I know, the cards implement ISO 14443a and there a anticollision mechanisms provided. Somewhere I read, that the reader must be able to detect the position of the collision, I guess since the Proxmark says "Multiple tags detected. Collision after Bit 16. iso14443a card select failed" that it is possible with the Proxmark. Am I right?

Actually, I don't need anticollision in the meaning of "numbers of tags and tags themselves are unknown". I just want to test, is tag with id = xxx there or not, so I need something like "answer on request". I'm not bound to the Desfire chips, I just used them, because they were available by my college.

So, can someone help me smile!?

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#2 2015-01-16 13:41:49

iceman
Administrator
Registered: 2013-04-25
Posts: 6,697
Website

Re: Read multiple Tags

Depends if you did implement the suggested fix for anti-collision mentioned on  the closed issue https://github.com/Proxmark/proxmark3/issues/43   .  I don't think Holiman pushed it to the Pm3-master yet.   But it is a small fix.


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#3 2015-01-16 16:19:39

J4CK
Member
Registered: 2015-01-09
Posts: 3

Re: Read multiple Tags

I've now updated the line. I get the same collision warning and 1 card.

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#4 2015-01-16 16:31:16

iceman
Administrator
Registered: 2013-04-25
Posts: 6,697
Website

Re: Read multiple Tags

Collision warning and 1 card ???   Are you sure, you don't mean 2 cards?

Sadly I can't help you with it, since I don't have 2 desfire tags to play with. sad


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#5 2015-01-16 18:35:37

piwi
Contributor
Registered: 2013-06-04
Posts: 704

Re: Read multiple Tags

Hopefully he means that now 1 card is selected.

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#6 2015-01-19 16:03:14

J4CK
Member
Registered: 2015-01-09
Posts: 3

Re: Read multiple Tags

Yes, this is what I meant. I can see 1 card out of 2 or 3.
For example, when I use "hf 14a reader" with 3 tags, Proxmark answers:

#db# Multiple tags detected. Collision after Bit 16
#db# Multiple tags detected. Collision after Bit 4
ATQA : 44 03
UID : 04 7d 68 5a 78 1f 80
SAK : 20 [1]
TYPE : NXP MIFARE DESFire 4k | DESFire EV1 2k/4k/8k | Plus 2k/4k SL3 | JCOP 31/41
ATS : 06 75 77 81 02 80 02 f0
       -  TL : length is 6 bytes
       -  T0 : TA1 is present, TB1 is present, TC1 is present, FSCI is 5       
       - TA1 : different divisors are supported, DR: [2, 4, 8], DS: [2, 4, 8]   
       - TB1 : SFGI = 0, FWI = 8
       - TC1 : NAD is NOT supported, CID is supported
       -  HB : 80

Is it possible to get all 3 tags selected one by one?

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