Possible security feature for NFC ring: audible/visual signal when read?



  • So a very long while ago I watched a lecture from Kristin Paget displaying a technology that she describes as "Guardbunny". I'm not one for frivolous commercial brand names, but what drew my attention was what it does. I won't bother you with any pathetic attempts made by me to explain it in technical detail of how this Guardbunny product works (do see the demo and explanation in the link below for that), but it basically offers three protection schemes: jams signals of unwanted read sessions, makes an audible signal when the tag is being attempted to be read, makes a visual signal when the tag is being attempted to be read (a light turns on).

    The demo:
    https://youtu.be/HRXb-FZ6WFM?t=40m20s

    Anyone who knows this field is probably aware that we'll never be able to (fully) defeat unwanted RFID/NFC interactions, so it would be nice to at least know when our tags are being read, so we can make due changes if the read session was unwanted. Therefore the latter two of the three protection methods sounded very intriguing.

    Would it be possible to build in a system in future ring models that makes an audible and/or visual signal when there's a read activity in progress?
    As you could see in the demo, it doesn't require any extra power or such, but probably boils down to matters of available space in a ring design, cost, and having the required technical know-how to implement.


  • Community Helper

    That was an interesting video. I've corrected a couple ambiguous portions of your post, those who want to google Kristin can.

    So in the video she's referencing 125kHz RFID which is a little different to 13.56MHz NFC. It's possible to do a similar thing (I modified a tag a while back with an LED instead of an IC wafer) but you'd have to play around with it to see if you got consistent results with cards.

    With the rings though, totally different story.
    You get a little bit of cross talk due to the proximity of the two inlays already but if you were to try to add in something like this to the ring itself things get a little more complicated - you'd have to have a system to switch it on and off if it's in the ring. Or to switch the IC out for the LED, lets say, because running the LED as well as the wafer doesn't leave much power for the thing you actually want to do and makes it slightly more difficult to get a good read. It'd have to be done in such a way that it didn't ruin the tuning of the antenna so that you could still read the ring when you want to. It's difficult. And all this inside the body of the ring.
    You could go the other way by wearing an extra, ring cover over the top of the real ring but now it's just getting really inconvenient. Ring cover has to be large enough to go over the top of real ring, ring cover is going to be chunky and feel really off.


  • NFC Ring Team

    What Lokki said pretty much.



  • As per my experience you get a little bit of cross talk due to the proximity of the two inlays already but if you were to try to add in something like this to the ring itself things get a little more complicated .
    You should have to have a system to switch it on and off if it's in the ring.
    Also you can try to switch the IC out for the LED, because running the LED as well as the wafer doesn't leave much power.

    pcb prototypes


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