More than four years have passed since the publication of the first part about the EM4100, and I still decided to write the second part - about the implantable NFC.

The advantages of the first 125 kHz tag were immediately noticeable - the key to intercoms and internal locks, but I wanted more - unlock the phone, laptop, store data in a secure place. All this allows you to make a standard NFC tag.

More about the implantation process without the help of outsiders, the use and disadvantages are under the cat.

ATTENTION! This publication is not an instruction, recommendation, guide to action and is intended for reference only. Repetition of the following can be deadly or lead to complications and injuries. The author does not recommend performing the described actions on himself and is not responsible for any consequences caused by reading the publication.

NFC, ISO14443 and Mifare

Standards of short-range radio communications and wireless tags in particular, there are a great many. The most commonly used frequencies are 125 kHz (LF band, see the first part, the most frequent representatives are EM-Marin, HID Proximity), 13.56 MHz (HF band, representatives are the Mifare family, HID iClass family) and 860-960 MHz (UHF band).

In general, within each range there is such a light mishmash of ISO standards, extensions of ISO standards to other, but compatible, commercial names of families and products that partially or fully implement one of the standards. This can add complexity and unexpected problems when you expect your label to open this door, and the standard is actually not quite the same - and nothing works.

Let's briefly go over the main standards:

ISO 14443 - one of the basic standards for wireless access cards, defines the operating frequency (13.56 MHz), limit distance (10 cm), other physical interface parameters, speeds (up to 106 kba / s in the original standard) and data transfer protocols between reader and card, collision detection, if there are more than one card in the reader field, etc. The standard does not stipulate the encryption used, as well as the exact format of the data on the card.

ISO 15693 is a less common standard, incompatible with the previous one. It assumes the same operating frequency, but a lower data exchange rate (up to 26 kbaud / s) in exchange for a longer reading range.

NFC - Near Field Communication - a fairly large set of standards, partiallycompatible with ISO 14443, describing both the physical level of the interface (generally based on ISO 14443), and much more, the NDEF data storage format (standardizing methods for encoding URLs, contact details, etc.), compatibility mode with ISO 14443. to the latter, each NFC device (both a RFID tag and a smartphone) can at least return its identification number in an understandable format for older cards. Well, usually an NFC reader can read other RFID cards that are not NFC, but also based on ISO 14443.

MIFARE - a large family of standards, also based on ISO 14443, characterized by a memory size (from hundreds bytes to tens of kilobytes), encryption (from a missing or proprietary algorithm to AES \ DES), often used as access cards, payment cards.

xNT Glass NFC Tag

On KDPV it is he. A smooth 2x12 mm glass cylinder containing a standard NXP NTAG216 chip and compact antenna is delivered immediately in sterilized form inside a special syringe.

The label in this design was made by the guys from Dangerous Things during the Indiegogo campaign , which raised more than $ 30 thousand with the required $ 8 thousand.

In 2014, after the implantation of the EM4100, this chip was found, was ordered and successfully arrived by Russian Post to me. It cost then $ 99 (the same costs now) plus $ 28 delivery.

Implantation process

And here it is - in fact, none of this will be needed! This is a photograph of the tools from the first part of the article.

Since the label comes already sterilized in the syringe, its implantation is much simpler, it is performed independently without any problems without any help. In general terms, the process looks something like this:

• Select a label placement. As already mentioned in the first part, most often choose the space between the thumb and forefinger, as this place usually does not feel pressure in everyday life. If there are more than one tags, like mine, it is undesirable to place them very close, it is better to retreat 1-2 cm from each other.
• Novocaine anesthesia - we inject a solution of novocaine 20 mg / ml subcutaneously at the proposed site of the incision, simultaneously pushing the tissues apart and simplifying further label placement, we wait for 5-10 minutes to penetrate the surrounding tissues. Be careful with novocaine - if you have allergies and / or crooked hands can cause many of the most unpleasant consequences, even fatal! Do not do this yourself if you are not a doctor. Also, do not do this alone and be prepared to call an ambulance, if that.
  
  In principle, anesthesia can be skipped; it is not so difficult to survive the injection of a thick needle into the arm. In this case, it is desirable that the introduction of the label still not be done by you, but by the other person - to make a skin fold with the other hand.
• Implantation - we rub the skin twice with alcohol, pierce the skin fold or “bubble” with novocaine, holding the needle almost horizontally to the skin, insert the needle 15-20 mm, then, pressing the syringe plunger, squeeze the mark through the needle under the skin. Carefully remove the needle.
  
  Here is a video (not mine) about how it looks:
  
  
• The completion - the incision in this case is even smaller than it was the first time, so it’s enough just to glue it with adhesive tape. If everything was done correctly, after 3-5 days the patch can be removed, and only a small scar will remain on the skin, which will disappear completely after a few months. If during these days the temperature rises - again, we go to the doctor, without delay.

How was it with me

Having some knowledge in medicine, I decided to do everything myself. Actually, no problems arose :) Those who wish to repeat - for the third time I will propose to re-read the warning at the beginning of the article.

Smartphones and laptops

Further - how to apply it? Most of all, I was interested in the possibility of using tags for quick unlocking of technology - fingerprint sensors were not everywhere in 2014, there were none in my smartphone and laptop.

Those programs that were in 2014 are no longer in an active state, so I’ll simply describe them in general terms.

NFC on Android - xNT - is an ordinary and quite full-fledged label, so all the programs that you can find in the market at the request of NFC - work. You can store some information in your tag (for example, a private key for something, although it may not be very secure), you can automate actions when bringing a tag to the phone.

Android NFC Unlock- in the market at the request of “nfc unlock” or “nfc logic” programs that fully perform this function, and for some time I used it on my HTC.

Unlocking Windows via NFC - here are two features. First, NFC tags are not considered full-fledged smart cards, and a third-party “provider” is required for their work. Secondly, Windows does not allow the use of a smart card for local login, without a domain. Therefore, third-party software is required. I used a bunch of NFC Connector and EIDAuthenticate , and as a reader - ACR-122U.

Disadvantages and problems

I am using the EM4100 label now. And the xNT Glass NFC Tag is not, and here's why:

• A very small radius of action - in fact, you had to move your hand for a while on the reader or on the back of the smartphone until the mark is finally in the right position. My first 125 kHz tag worked much more stable.
• The lack of support in the standard software - for both Android and Windows, third-party software was required, which in the first case was quite "collective farm" and slow, and in the second - paid.
• Distribution of fingerprint readers - even if they are less secure (try to roll the smartphone on the arm of a sleeping person with an effort, looking for that point!), But there is “out of the box” and the security provided by them was sufficient for me.

In general, about five years with tags

About the relative futility of the NFC tag is written above. Otherwise, no particular problems. In almost five years, nothing happened with the marks or with the hand itself, the scars disappeared long ago, and no special pitfalls were found either. Yes, it is still more convenient to open the door with your hand than with a separate tablet. Yes, they can be used even in organizations as a pass, offering to register “your card” in the ACS and causing a slight surprise - but no more.

If you have questions - ask, I will try to answer :)