Writable RFID Tags for door entry keyfob?

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George Jackson

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Apr 26, 2021, 9:05:52 AM4/26/21
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Hi I bought this RFID card copier with the intention of cloning the keyfob for my apartment's door entry system and then copying this to a thin flat RFID sticky pad that I could then put inside the case of my phone so that I could 'use my phone' so to speak, to open my door, rather than always fumble around in my pocket for the keyfob. (Also since I use my phone for most things already anyway).


So I also got these:


But they don't work. The copier won't write to them and I think maybe they are only readable?

The cloner will write to the tags it was supplied with no problem. But the casing for these is too thick to hide inside my phone case.

Can anybody suggest an alternative that should work and that I can preferably source in the UK? If not I will buy from anywhere? Having a few in a pack would be useful, as I can give some of them to my neighbours maybe.

George

David Pye

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Apr 26, 2021, 9:19:05 AM4/26/21
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Hi George,

The spec, as I understand it, says the cards should *not* be writable - in the sense that the unique ID should be pre-set to make cloning harder.
As you've found, the plastic 'chunky' supplied ones are editable, but they're usually the exception rather than the norm.  Lots of the usual Far East sources supply ones you can write to - ie clone.
I've found a few others listed as writable but no obvious UK source ones.


says they are writable.

Alternatively, you could try and trim/chop the case off one of the chunky ones and see whether the 'inside' is something you could mount in a phone case?

Regards

DAvid

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Alistair MacDonald

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Apr 26, 2021, 9:20:46 AM4/26/21
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I have done this with some Mifair classic tags but not any 125Khz ones.

I am surprised that these tags are writable as normally you would expect then to be fixed unless sold otherwise. I guess it could be different for the 125Khz ones. Can the copier tell you the ID if the tag? I did a hack on the penguin run where I had a door entry reader read the tag and had an Arduino Mini sniff the data going between chips on the board. If you have any kind if reader this might be an option to check the ID.

Another think that is a thing in the Mifair world is some readers will reset a fob before reading it to stop copies working. This way a fob that can copy another fob will not work. It is kind if a cat and mouse game in the low cost market.

All the best,

  Alistair





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George Jackson

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Apr 26, 2021, 2:49:48 PM4/26/21
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says they are writable.

>>>>>>>>>>>>>>>>>>>>>>>

David isn't that what I just bought in the other ebay link I shared here?

Are these different somehow?

George

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David Pye

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Apr 26, 2021, 2:51:53 PM4/26/21
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Hi George,

Yes, I believe they are.

As I said, the official standard says they should be read-only.    The ones you linked to say 

"
  • 125Khz operating frequency
  • Pro-programmed with unique ID number
  • EM4100 Standard

"
To me, that says they are read only.

The ones I linked to, specifically says:
5pcs 25mm 125Khz RFID Tags T5577 Writable Stickers Proximity Cards Rewrith3


So, if they deliver what they say they will deliver, those should have an ID that can be edited.

(If...)

David


George Jackson

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Apr 26, 2021, 2:52:21 PM4/26/21
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Alistair, no there is no digital display to show the tag id, The available functions are 'read' and 'write' and that's all.

On Mon, 26 Apr 2021 at 19:49, George Jackson <jebus...@gmail.com> wrote:

George Jackson

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Apr 26, 2021, 2:54:35 PM4/26/21
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OK David, I will probably give them a go. This is something I have long wanted to do. It will save much fumbling around in my pockets.

George

Alistair MacDonald

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Apr 26, 2021, 2:56:07 PM4/26/21
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For a few quid I would hurt get some that explicitly say they are writable. They are physically identical. The ones you can change have just not had the setting changed to make them read only.

All the best,

  Alistair


George Jackson

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May 29, 2021, 5:34:41 PM5/29/21
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OK, well that worked out great. I can now open my door with my phone, or at least give the very close appearance of doing so.

Thanks guys.

From: north-ea...@googlegroups.com <north-ea...@googlegroups.com> on behalf of Alistair MacDonald <alistair....@gmail.com>
Sent: 26 April 2021 19:55
To: north-ea...@googlegroups.com <north-ea...@googlegroups.com>
Subject: Re: [Makers] Writable RFID Tags for door entry keyfob?
 
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