Proxmark3 community

dontlook

Contributor

Registered: 2017-01-28

Posts: 57

Problems writing to t55 in Jakcom ring

I picked up one of the Jakcom rings because it seemed like fun and it is making me a little crazy right now.

Got it out of the box and immediately struggled to read the tag.  This is nothing new to me with small t55xx tags, but the ring format was hard to position over the antenna and stay in place.

I ended up using the foam the ring came in to hold it in place.

To start the Proxmark couldn't detect anything and write were not taking to the chip, so I switched to my white cloner with the display to see if the chip was working.  It has better success sometimes, but it can't wipe tags(just over write), and it puts a password on the chip.

So that writes successfully, and change the value by cloning a new card on to the chip.

....

Back to the Proxmark.  I can get reads with

lf search

that the card.

lf t5 detect

doesn't find the chip(i haven't moved the ring/chip).

lf t5 write b 0 d 00148041 p aa55bbbbb
lf t5 wipe

run without error.  I've removed the password from FOBs and full-sized cards written to by this device before, and that is the password it uses.

At the vendor suggestion I have manually set the config

 lf t5 config b64 d ASK i 0 o 1

I've run through these steps multiple times and at the end of the day

lf search

still returns the last value written by the cloner.

Any other suggestions?  Strange to me that I can read the value from the chip but can't write to it.

Last edited by dontlook (2018-03-15 18:11:44)

marshmellow

Contributor

From: US

Registered: 2013-06-10

Posts: 2,302

Re: Problems writing to t55 in Jakcom ring

The Reading that is working doesn't require the tiny chip to hear any commands from the pm3.  But writing certainly does. (As does t55 detect)

Basically the chip cannot hear the pm3 commands with the pm3 antenna you are using.  (Not well coupled)

dontlook

Contributor

Registered: 2017-01-28

Posts: 57

Re: Problems writing to t55 in Jakcom ring

Thanks marshmellow.  I can't seem to read pages individually either.

I was afraid that was the answer.

At least I have something else to program it with for now.  I'll look into antenna building or maybe the new Proxmark will be better.

marshmellow

Contributor

From: US

Registered: 2013-06-10

Posts: 2,302

Re: Problems writing to t55 in Jakcom ring

To read specific pages the tag needs to hear the page read cmd from the pm3 as well.

marshmellow

Contributor

From: US

Registered: 2013-06-10

Posts: 2,302

Re: Problems writing to t55 in Jakcom ring

A well built antenna specifically for small lf tags is important for the current hardware.  (And then it works quite well.)

Spyder

Contributor

Registered: 2017-12-20

Posts: 21

Re: Problems writing to t55 in Jakcom ring

See post http://www.proxmark.org/forum/post.php? … &qid=30987

Tom5ive managed to do what you are trying to achieve:

From post:

You need to issue the unlock command in test mode with these rings when the chip has been put in
EM / ID mode.

See below command:

lf t55xx write b 0 d 00148041 p AA55BBBB t

The stock proxmark coils probably wont cut it either! For a coil that is very close to perfectly tuned for the pm3 (needs a few wraps unwound, 2-3 should do it - test using hw tune etc) get yourself one of the coils linked below - it's what I used to unlock this ring.

http://www.ebay.com.au/itm/10pcs-125KHZ … SwA3dYDxYX