NFC Ring Unlocks Your Phone

NFC Ring

This little ring packs the guts of an NFC keyfob, allowing [Joe] to unlock his phone with a touch of his finger.

The NFC Ring was inspired by a Kickstarter project for a similar device. [Joe] backed that project, but then decided to build his own version. He took apart an NFC keyfob and desoldered the coil used for communication and power. Next, he wrapped a new coil around a tube that was matched to his ring size. With this assembly completed, epoxy was used to cast the ring shape.

After cutting the ring to size, and quite a bit of polishing, [Joe] ended up with a geeky piece of jewelry that’s actually functional. To take care of NFC unlocking, he installed NFC LockScreenOff. It uses Xposed, so a rooted Android device is required.

We’ll have to wait to see how [Joe]’s homemade solution compares to his Kickstarter ring. Until then, you can watch a quick video of unlocking a phone with the ring after the break.

31 thoughts on “NFC Ring Unlocks Your Phone

    1. I know nothing but the most general terms about NFC. So, please pardon the stupid questions. How’s the antennae incorrectly oriented? How could you tell? How is it supposed to be oriented?


      1. I’m guessing based on all other RFID/EMF implementations that the antenna is normally oriented flat/parallel to the reader(‘s coil), this design has the antenna in the Z dimension. i.e. it acts as a poorer antenna in relation, but well enough for this purpose.

    2. My understanding is that an em /wave propagates in two spheres from a standard antenna. The front facing sphere gets reflected /absorbed by battery and phone body, the back one does the induction and reading

    1. Will try to use the outer ring of a ball bearing (stainless steel).. Induction will probably be a problem (e.g. no reading the tag). If it works one still needs to cover the wire+ chip.
      Only easy way to beautify (although I like the geeky aesthetics of the clear resin coverd electronics) is to use colored resin for the top layer

      1. RE Ball bearing: bare in mind materal type & mass will also affect tuning, yep induction wont work, we have a custom polymer we use to solve this problem.
        RE Resin: I also really like the asthetics of a clear / transparent ring, that’s basically what we use on the NFC Ring :)
        Just be careful wearing any resin ring, I did create a bunch of similar rings but when I sweated my skin would break out in a rash ;\

        Happy to support you hacking further buddy if you ever do want any help just bump me, would love to create a wiki/tutorial to help others create similar projects

  1. This one is a definite win, I wonder if he can put a coat of silver or gold paint and then a layer of resin so that it looks like a traditional ring. metal will act like shielding and make the rfid stop working.

      1. Put a break in the conductive coating and hey presto, no problem.
        If you don’t, the well coupled (albeit lossy) loop will change the frequency and deQ the resonant tank.

  2. Doesn’t it use a whole lot of battery to run the NFC transmitter all the time? That ring is a passive device and needs a carrier signal before it does anything, and keeping the NFC chip online all the time wastes energy.

    1. You probably only need to ping for NFC card a few times a second and just a long enough burst for to detect a presence.
      “NFC and RFID Reader Ultra-Low-Power Card Presence Detection Using MSP430 and TRF79xxA”
      > This turns on the transmitter for approximately 20 µs.

      Very low duty cycle means a very low *average* power consumption. Only after establishing that, you would turn it on and do the whole song & dance to get whatever your need.

      1. Even so, you’re comparing it against very low average power consumption in the first place, considering you’d want your phone to operate for a week on a charge.

        Or at least, I wouldn’t use a phone that has to be recharged more than once a week to remain operational.

    2. Depend on your phone. My NFC was on and last at least all day. (but I don’t used it)
      Previous phone did not had a really good battery life (did have NFC neither) but your concern can be indeed a concern.
      All depend on phone and personal pref.

      Thinking of “Upgrading” my wedding band with it!

    1. Every tag have a unique ID (more or less). So unless someone reads the ID on your ring, record it, and create another tag with the same ID, you are safe.
      As they stated on the project, the range of the ring is very limited, so is very improbable that someone can read the ID without putting the reader in your hands.

      1. Someone could trick you into holding an innocent-looking object that’s also an NFC reader. Or, may be the reader is somehow implanted in one’s hand and all someone needs to do to steal your NFC code is to shake your hand. (c:

        1. Yes, it’s possible to create a innocent looking NFC reader, but I don’t think it would be possible to conceal a reader on the hand, the reader is a little bulky. But it would be easier to someone to steal your phone, or steal your ring and phone at the same time.

        2. It’s possible to do secure stuff over NFC (as that’s what your NFC-enabled bank cards do). However, most security pass implementations just read the ID on the card.

          It’s theoretically possible to clone a card if you build some custom hardware, but there’s no need to go all tin foil hat on how it can be hacked. It is considered secure enough for what’s required. Your phone is not Fort Knox, so reading a card ID will do.

          It’s also reasonably easy to copy a physical key by pressing it into plasticine or even taking a photo of it. They’re still considered secure enough for your front door.

    2. You’re overthinking this. It’s not intended to be secret military base secure, as 0xfred observed.

      Furthermore, though, with any security risk you can’t just say “how could I access this.” You have to also ask “why would someone want to access it” and then “what else would they be willing to do.” If someone is willing to put together custom hardware just to access your phone, as in your phone in particular, they have some reason for picking you as the target. Maybe they know or think they know you have something. Maybe they’re insane and think you’re the antichrist. In any case, imagine a scenario where someone motivated enough to spend time and resources to target you in particular but wouldn’t be willing to just threaten you with a gun or even a knife or a bat and demand you unlock the phone for them. The range of threats you’re failing to defend that *could actually reasonably be defended against* is fairly small.

    1. It should be easy enough. You can see the chip and coil through most NFC stickers. The coil looks smaller so I’d suspect you’d get less range. It might be more fragile. The fob used looks like the ideal candidate, but if you happen to have a sticker lying around…

      1. of course the ultimate would be to have this in a green lantern like ring that glows when the connection is confirmed…however I don’t think you’d get all the parts inside, along with keyfob or sticker guts to make it a reality….shame that.

  3. I wonder if you can just use the data from your passport/IDcard or bankcard RFID as an ID for your devices, I think you can just read at least a good chunk the basic data, so that flaw can be used to the hobbyist advantage. Then you can use something you might already carry.

    1. You can use any old card that gets supported by the Smartphone and the installed NFC app. It then only works with your Phone, though. The app only needs to know the ID of the card. All information – what actions are triggered – is saved in the app then with the ID of the card as the reference.

  4. Hey, I just made one after your tutorial, but it doesn’t work. I tried it with the wire from the key fob but it was one turn too short to fit a ring and the only wire I had around was copper wire with 0,5 mm (0,019 inches). I tried that with 11 turns for a diameter of 21 mm (0.826 inches). It didn’t work either.
    How can I calculate what copper wire I need (diameter and length/turns).
    As you see, I’m no expert in any of this. Info on this or a link would be brilliant!
    Thanks in advance! (✿◕‿◕)

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