Gear we Like: Just a Black Disc (NFC Tag)

Reviewed by Wndsn staff, Germany

Today we are continuing our discussion on high-impact, low-detection methods for digital security. Here at Wndsn we believe that the smallest, most innocuous items can have a critical impact in high-risk or high-stress situations, or when discretion is absolutely required. Let’s get started.

An NFC tag is a small, passive transmitter that can store a small amount of data. It does not send out any information. It only becomes engaged when connected to a reader. Once connected, it is readable and re/writable. NFC tags have been used for a large range of inventory-tracking purposes, from libraries to your Amazon warehouse, to mobile payments, to home automation.

So far, so boring.

An NFC tag can be used in two general use cases:

  1. Storing data for later or repeated use.
  2. Sharing data with third parties.

Typical data being written to those tags include:

Wifi credentials, phone settings for automated tasks, electronic SIM cards, passcodes, keys, bitcoin and altcoin addresses, coordinates for a location, etc.


The Black Disc by OscarDelta takes it a step further and makes an otherwise unremarkable NFC tag quietly exciting. It’s Just a Black Disc, an NFC tag enclosed in a circular plastic mold, and generally quite robust. The device can be written to and read from with any NFC capable mobile phone, it can be rewritten, password protected and made read-only. The nominal reading distance is "up to 100 mm" (about 4 in), but in reality, one usually has to physically touch the reading device (typically built into or next to the battery on a mobile phone) to get a connection to the disc.


The disc is robust, it is completely waterproof and flame-proof to an extent. You can leave it in your favorite pants in the wash and it will still work.

The disc is undetectable, including through hand-held or walk-through metal detectors, hence making it suitable for discreet or covert communications.


The available storage space is "up to 137 bytes", that is 137 characters. There is no space (or reason) to put actual files or documents on such an NFC tag. Also, operating the disc is only possible from very short distances.


NFC tags are not made to store any significant amount of data (there are other, similarly small devices available for that purpose), but the tags are very useful for the aforementioned types of data. In addition, they can be used for authorization and/or authentication purposes, as a physical token (here, making use of the limitation of operating distance to enforce its physical presence) that can be read and verified as part of a more complex security plan.

Espionage professionals of yesteryear wish they had it so good. Carry (embedded into a larger strategy and set of procedures of course) the Black Disc safely, in the knowledge that you are controlling the information that you need in just the way you need it.


A simple hack, courtesy of the ever ingenious @mimtwin: add a self-adhesive piece of velcro (hook) to the black disc and fix it to a velcro (loop) field. Add a morale patch on top for concealment. The disc shown is scannable through the leather Vegvisir patch.


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