VivoKey Spark Left or Right Hand?

So, I’ve got an appointment with a registered implant installation partner for the first week of November to get a VivoKey Spark installed. After several months of research and playing around with an NFC ring and a Proxmark3, I opted for the Spark as it seems like the most secure and extendable option out there. Plus, I’m a software developer… so I’m particular excited to play around with the APIs.

As far as immediate functionality goes, I think I’ve set my expectations appropriately (low). I plan to set it to just redirect to a URL upon scan, specifically pointing to a VCF text file hosted at my site. That should basically be the same end result as using NDEF on an xNT where the VCF is stored on the implant itself… save for the fact that the smartphone’s browser would briefly open to download the VCF. Does that sound about right?

Ultimately, I’m interested in contact-less payment, but I’m assuming that will require the VivoKey Flex.

So with those two use-cases / goals in mind, I have two questions:

  1. Which hand would you recommend I get the Spark installed in? I’m predominantly right handed (although nearly ambidextrous)

  2. If I eventually get the Flex, can the Spark and Flex be installed in the same hand? If so, using my right hand seems like the logical choice. Seems like it probably could, as the Flex appears to go more on the forearm, if I’m not mistaken? A fair distance from the webbing between your index finger and thumb (Spark location).


There is no right answer it’s all personal preference.
Due to the features of the spark and flex will mostly be used to read with a phone, mostly your phone. What side and location would that be easiest for you?

Personally I’d have them both installed in the forearms. Leave your hands for tags you’'ll use primarily for access control. (xNT/xEM) as you’ll need the extra positioning manipulation.


I also wanted to do this, but I discovered last week that iPhone (with the latest software) will let you open the VCF file, but it will NOT let you save it!
This was a disappointment for me, because it means I can’t use a VCF file on my website + my implant as a “business card alternative”.

Android works as expected tho: it lets you open the VCF via URL AND save the data once opened.



Access control is, unfortunately, not an option for me. I don’t own a car (a blessing on that front lol) and I rent and can’t modify my locks. My apartment does use a keyfob with two tags on it, but it uses Hitag S 2048/Mifare 4k and can’t be cloned as far as I know. My attempts at getting management to write the tags onto my NFC ring, were equally unsuccessful.

Regarding the position / placement of the implants… am I correct in assuming that a Spark could be installed in my right hand with a Flex in my right forearm? (If I end up needing both)

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You can safely implant two HF tags (Spark & VivoKey Flex) in the same arm without interference. You would only have to worry about collision (the phone fighting over which tag it wants to communicate with) if the tags were less than an inch apart. Even then, they would likely require different orientations of the reader antenna to couple appropriately.

I have a NExT in the webbing of my hand and a flexDF on top of my forearm behind the wrist ~3" away and I never have to deal with crosstalk, even when using a powerful ACR122U reader.


Awesome! Thanks!

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Definitely possible, just not so close to each other that the phone or reader may pick them both up when attempting to read one of them.

Is there a file format that Apple DOES approve of that you can open via browser and save (like their ical files for appointments?)

Unfortunately I don’t know that. I learned this about VCF the hard way + some googling.

Can you export contacts on your iPhone to any kind of file format? If so, what are the options?

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