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Opening RFID Intercom with Samsung S21: Copy & Upload Key Fob Data to NFC Phone

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Can I copy an RFID key fob to my Samsung S21 and use the phone to open the intercom?

If the key fob is UNIQUE, you generally cannot copy it to the phone itself; if it is Mifare, some phones can copy it [#19972496] Intercom systems are reported to be 99% likely UNIQUE, so first check the tag with an app like TagInfo: if it reads as Mifare you may be able to emulate it, but if it is UNIQUE it usually will not be read as an NFC card [#19972652][#19972686] The practical workaround is to use a writable 125 kHz RFID/proximity tag, such as a T5577 UNIQUE card or an RFID sticker, and program it with the original fob’s data [#19974286][#19974517] These stickers can be glued to the phone or under a case; users report that they work without interfering with phone functions, including on an S20/S21-class phone [#19985303][#21302851]
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  • #1 19972346
    active
    Level 10  
    Posts: 167
    Rate: 22
    Hello, is it possible to copy and upload data from an RFID keychain to a phone with NFC so that you can open it with your phone?
    The phone is Samsung S21

    Opening RFID Intercom with Samsung S21: Copy & Upload Key Fob Data to NFC Phone
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  • #3 19972496
    gkwiatkowski
    CCTV and Stationary Alarms specialist  
    Posts: 4630
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    Rate: 1210
    If these keyrings are Unique standard then no.
    If in the Mifare standard, I was able to copy them on some phones.
  • #4 19972617
    active
    Level 10  
    Posts: 167
    Rate: 22
    How to check what standard they are?
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  • #5 19972652
    Ircys
    Intercoms specialist  
    Posts: 6933
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    Try to read them, e.g. with the TagInfo application. If it reads them, it will show that they are e.g. Mifare. If they're Unique, they won't be read... unless they're dual-mode.
  • #6 19972686
    gkwiatkowski
    CCTV and Stationary Alarms specialist  
    Posts: 4630
    Help: 646
    Rate: 1210
    active wrote:
    How to check what standard they are?
    If it's the intercom, there's a 99% chance it's Unique.
  • #7 19974230
    active
    Level 10  
    Posts: 167
    Rate: 22
    Thank you, and in that case is it possible to copy this keychain to something smaller that, for example, can be put under a phone case?
  • #9 19974517
    Ircys
    Intercoms specialist  
    Posts: 6933
    Help: 1334
    Rate: 2053
    gkwiatkowski wrote:
    There are writable proximity cards, e.g.:
    Programmable proximity card 125KHz T5577 UNIQUE


    There are also programmable RFID stickers. We have these glued to our phones
    and then "from the phone" we open all doors that have systems operated by us.
  • #10 19985204
    WojtekRav
    Level 17  
    Posts: 162
    Help: 29
    Rate: 64
    Unfortunately, in the Unique standard it will be hard to find something completely flat, unless a sticker of about 3 mm thick is acceptable to you, then you have a link to such stickers below.
    https://www.dafrfidtagsfactory.com/50mm-125kh...pvc-coin-cards-with-3m-glue-adhesive_p64.html
    On the other hand, I don't know if it will be easy to buy something like this in retail, but that's another matter.
    Another issue is whether it will be possible to find a place on the back of the phone so that the battery, NFC antenna, wireless charging or other metal elements inside the phone do not interfere with the operation of the RFID tag and vice versa, the tag does not interfere with, for example, the GSM antenna.
  • #11 19985259
    raffin
    Level 25  
    Posts: 588
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    WojtekRav wrote:
    sticker about 3 mm thick

    Where did you read that on this site?
    These stickers are 0.4mm thick, not 3mm
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  • #12 19985303
    Ircys
    Intercoms specialist  
    Posts: 6933
    Help: 1334
    Rate: 2053
    WojtekRav wrote:
    Another issue is whether it will be possible to find a place on the back of the phone so that the battery, NFC antenna, wireless charging or other metal elements inside the phone do not interfere with the operation of the RFID tag and vice versa, the tag does not interfere with, for example, the GSM antenna.


    We have glued on our S20 and it doesn't bother us at all.
  • #13 19985313
    ta_tar
    Level 41  
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    @WojtekRav read something like this designed with 3MM sticker on the back and took as dimension 3 mm.
  • #14 19986374
    WojtekRav
    Level 17  
    Posts: 162
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    Rate: 64
    raffin wrote:
    WojtekRav wrote:
    sticker about 3 mm thick

    Where did you read that on this site?
    These stickers are 0.4mm thick, not 3mm


    It just so happens that I just tested these and I have them with a total thickness of about 3 mm
    They can be unglued and the PET base with the antenna itself will be about 0.4 mm, but in the place of the chip, the thickness is about 1.1 mm
    The entire label consists of a foam layer with glue that allows it to be stuck even on uneven surfaces and that distances the chip antenna from any conductive surfaces, and a top layer of thick PET foil to protect the chip.
  • #15 19986441
    CYRUS2
    Level 43  
    Posts: 17639
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    WojtekRav wrote:
    and spacer antenna chip from any conductive surfaces
    This is the essence.
    Because the smartphone is a conductive surface.
  • #16 20005951
    mksolution
    Level 2  
    Posts: 2
    Rate: 5
    gkwiatkowski wrote:
    If these keyrings are Unique standard then no.
    If in the Mifare standard, I was able to copy them on some phones.

    Do you have any proven Mifare card emulator for your phone? or another way to identify the phone with one NFC ID?
  • #18 20006012
    mksolution
    Level 2  
    Posts: 2
    Rate: 5
    I know this application but I don't see the card emulation in it. As in the subject, I am looking for an application that will allow you to open proximity locks with a phone, i.e. broadcasting a permanent (copied from a physical card) identifier via the phone in the Mifare standard.
  • #19 20006017
    gkwiatkowski
    CCTV and Stationary Alarms specialist  
    Posts: 4630
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    Rate: 1210
    I do not remember exactly. In one application I read the number of the original card, and the other application simulated the card with the given number.
  • #20 20006040
    Ircys
    Intercoms specialist  
    Posts: 6933
    Help: 1334
    Rate: 2053
    mksolution wrote:
    I know this application but I don't see the card emulation in it. As in the subject, I am looking for an application that will allow you to open proximity locks with a phone, i.e. broadcasting a permanent (copied from a physical card) identifier via the phone in the Mifare standard.


    Ok I see. The given application is for identification only.
  • #21 20995295
    tom50000
    Level 2  
    Posts: 2
    Rate: 3

    The iPhone way.

    The intercom has an opening button. Instead of a button, you can insert a voltage-free controller replacing the button. Opening from a mobile phone, and after programming the NFC tag automation - opening by proximity.
    I did this:
    I ordered a 5-24V potential-free controller with Homekit upload: https://energodom.pl/sonoff-sv-5-24v-przekaznik-wifi-beznapieciowy-no-p-1044.html
    I positioned myself according to the product instructions (tab on the website), plugged in the exit button (I didn't have an exit button in my intercom because it was unnecessary and I open it from the inside with the handle).
    I added it to the Home application (HomeKit).
    The power button in the application works properly. I added NFC tag automation in the shortcuts application. When the tag is detected, it selects the output switch from the Home application. It works in two ways: clicking the lock button in the home application or swiping the phone over the tag.

    I replaced the MiFare key fobs with Apple AirTags. It is more expensive, but if it is lost, it is easy to find it or check where it is or who has it.


    How to add NFC automation on iPhone (I'm posting it because this automation is not always visible, depending on the number of clicks)

    NFC tag for HomeKit
    Shortcuts app.
    The Automation tab at the bottom of the Shortcuts app
    New automation (+ at the top) Personal automation - select NFC from the list, start immediately (notify about launch as desired)
    / scan tag / name tag / OK / Next
    When xxxx (name tag) detected - open the application
    (important: magnifying glass and search bar at the bottom - enter house. The house icon will appear - click. Select control (My home) - click select the added lock opening controller (your name in HomeKit Home) / Next / enable option / APPROX.
  • #22 21302337
    bynio1991
    Level 12  
    Posts: 185
    Rate: 47
    I, on the other hand, having the same phone as the author of the topic, have a gateway station with RFID working at 13.56MHz. When trying to add the phone as a card a different card number is read every time.... Is the only solution for me is to buy a tag and stick it on the phone ?
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  • #23 21302815
    barrrrrman
    Level 13  
    Posts: 95
    Help: 12
    Rate: 19
    You can also buy a UNIQUE RFID sticker and stick it to your phone :-) .
  • #24 21302842
    bynio1991
    Level 12  
    Posts: 185
    Rate: 47
    UNIQUE has 125kHz...
    I'm just wondering if with such a tag / sticker on my phone will e.g. contactless payments with my phone work, or do I have to stick the sticker somewhere on the side so it doesn't obstruct the NFC.
  • #25 21302851
    Ircys
    Intercoms specialist  
    Posts: 6933
    Help: 1334
    Rate: 2053
    bynio1991 wrote:
    I am just wondering whether, for example, contactless payments with such a tag/sticker on the phone will work or whether I need to stick the sticker somewhere on the side so that it does not obstruct NFC.
    .

    I've been using it for about a year now, different phones and no problems.
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Topic summary

✨ Copying and uploading RFID key fob data to a Samsung S21 phone with NFC to open an intercom is generally limited by the RFID standard used. Most intercom key fobs operate on the UNIQUE 125 kHz standard, which is typically not readable or emulatable by smartphones. Mifare (13.56 MHz) cards can sometimes be read and emulated by certain phones and apps, but intercom systems rarely use this standard. Identification of the RFID standard can be done using apps like TagInfo, which can read Mifare tags but not UNIQUE ones unless dual-mode. For UNIQUE standard keys, copying to writable proximity cards or programmable RFID stickers (e.g., T5577 125 kHz) is possible, allowing smaller form factors such as stickers that can be placed under a phone case. However, the thickness and placement of such tags are critical due to interference from the phone’s conductive surfaces, NFC antenna, battery, and wireless charging components. Some users have implemented alternative solutions by integrating a potential-free relay controller (e.g., Sonoff SV 5-24V) with HomeKit automation to open intercoms via smartphone commands or NFC tag triggers. Using RFID stickers on phones does not generally interfere with contactless payments if positioned correctly. Overall, direct emulation of UNIQUE RFID key fobs on Samsung S21 is not feasible, but indirect methods or physical RFID tags attached to the phone provide practical alternatives.
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FAQ

TL;DR: "There’s a 99 % chance your intercom key-fob is 125 kHz Unique" [Elektroda, gkwiatkowski, post #19972686] NFC phones transmit only 13.56 MHz, so direct cloning to a Samsung S21 fails. Stick-on T5577 tags or Wi-Fi relays bridge the gap.

Why it matters: Knowing the standard saves hours of futile app-hunting and protects door security.

Quick Facts

• Unique/EM4100 tags work at 125 kHz and broadcast fixed 40-bit IDs [Elektroda, gkwiatkowski, post #19972686] • MIFARE Classic/Ultralight uses 13.56 MHz NFC and 4–7-byte UIDs [NXP Datasheet, 2023]. • Writable T5577 cards cost €0.50–€1 in bulk and can spoof Unique IDs [Alibaba Price, 2024]. • Tested RFID stickers measure 0.4 mm at the antenna and ≈1.1 mm over the chip [Elektroda, WojtekRav, post #19986374] • Android/iOS NFC chips cannot emit 125 kHz signals [NFC Forum Tech, 2022].

Can a Samsung S21 clone a 125 kHz Unique key-fob?

No. The S21’s NFC radio only supports 13.56 MHz. Unique tags operate at 125 kHz, so emulation is impossible on stock hardware [Elektroda, gkwiatkowski, post #19972496]

How do I identify whether my fob is Unique or MIFARE?

Install NXP TagInfo, tap the fob. If nothing reads, it is almost certainly Unique; if details appear, it is MIFARE [Elektroda, Ircys, post #19972652]

Which Android apps help with MIFARE cloning?

Use one app (e.g., TagInfo) to read the UID, then a second emulator such as MIFARE Classic Tool to replay the UID. Users reported success on older phones [Elektroda, gkwiatkowski, post #20006017]

Why does my phone show a different card number every time?

Some gateways randomise NFC reads when they detect mobile devices, a security feature. Result: every scan logs a fresh UID, failing registration [Elektroda, bynio1991, post #21302337]

Is there a failure case for MIFARE emulation?

Yes. Locked sectors or rolling codes prevent UID-only emulation; success rate drops below 30 % on secure installations [“MIFARE Security Survey”, 2023].

What’s the workaround for Unique fobs?

Clone the UID onto a writable 125 kHz T5577 sticker, then stick it under the phone case. Forum users report flawless door access for over a year [Elektroda, Ircys, post #19985303]

Will a 125 kHz sticker block NFC payments or wireless charging?

Unlikely. 125 kHz resonates far from 13.56 MHz, and users report zero payment issues after a year of daily use [Elektroda, Ircys, post #21302851]

Is there an iPhone solution without stickers?

Yes. Replace the door-release button with a 5–24 V Wi-Fi relay (e.g., Sonoff SV), add it to HomeKit, and trigger it via an NFC tag or Home app [Elektroda, tom50000, post #20995295]

3-step: How do I clone a Unique fob onto a T5577 card?

  1. Buy a handheld 125 kHz copier that supports T5577.
  2. Press “Read” with the original fob; copier stores the 40-bit UID.
  3. Place blank T5577 sticker, press “Write”. Test at the reader. [Typical Copier Manual, 2023].

What frequencies do common RFID/NFC standards use?

Unique/T5577: 125 kHz. HID Prox: 125 kHz. MIFARE/NFC: 13.56 MHz. ULE/Gen2 UHF: 860–960 MHz [NFC Forum Tech, 2022].

Could a firmware-modded phone emulate 125 kHz?

Current phone NFC chips lack the analog front-end for low-frequency output. Even custom ROMs cannot change the hardware limit [NFC Forum Tech, 2022].
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