02:16pm | 05/06/2020
Daniel Tompkins

media art DIY electronics

Oddly enough, I don't remember when or how I first got my hands on the Toshiba FlashAir card. These WiFi-enabled SD cards are made to transfer photos from a digital camera to a computer.

The Toshiba-made FlashAir, WiFi-enabled SD card

The Toshiba-made FlashAir, a WiFi-enbled SD card.

Imaginging that someone would use a 4MBps wireless connection to transfer photos when the hardware transfer is closer to 70MBps seems ridiculous.

However, it could come in handy if you're in a situation where you don't have access to an SD card reader, or want to easily preview photos on a phone or tablet.

Digging into the FlashAir

What's far more interesting about these Toshiba cards is the fact that they are essentially programmed to act as a wireless access point (WAP). You can setup a custom SSID and password— connecting directly to the card over 2.4GHz.

After peeking at the filesystem, I realized that the main photo gallery application hosted on the card is essentially a static website— served as basic HTML, CSS and JavaScript.

Screen-grab of the FlashAir filesystem.

Screen-grab of the FlashAir filesystem shows the basic components of a web server— HTML, JavaScript, CSS and other Web assets.

My excitement with this bit of tech was the possibility of building a totally discrete microserver that would be capable of hosting a few pages and services.

Project Inspiration

My fourth-year undergraduate architecture studio, entitled Dark Rooms, was taught by Mona Mahall. The studio was split into three exhibitions: Pyramid, Server and Backstage. These exhibitions were meant to explore the "spaces between visibility and invisibility".

In the second exhibition, Server, we were asked to consider the design of an anti-human space— a dark, cold, electronic archive built exclusively for machines. In my preliminary research, I was particularly interested in artists like Adam Bartholl.

His project, a USB "dead drop", drew inspiration from an information-sharing tactic used by spies. A predetermined secret location— such as a hollowed-out rock, brick, log or other object— would be used to discreetly stash an important item.

Image of Adam Bartholl's

Adam Bartholl's "Dead Drop" USB stick, embedded in the mortar of a brick wall

Once the item— perhaps a slip of paper or a key— is "dropped", a second party could then retrieve it without interacting directly with the other person or being detected in the exchange.

Wireless Anonymous Repository

While a USB is already a much more "invisible" way of storing and exchanging information, I wanted to take this concept a step further. Using the FlashAir cards, I proposed a new wireless dead drop that could be just as affordable and simple as the USB, but with a myriad of superior qualities.

Writing directly to the card requires an SD card slot; however, the wireless functionality can be powered without a desktop or laptop. A typical SD card takes 2.4-3.6V at about 30mA. I found that by using an SD-to-USB adapter, one could power the wireless module from a standard 5V USB outlet.

The FlashAir SD card (which I code-named, warTOR) powered up inside an AC electrical housing.

The FlashAir SD card is powered up by a 120VAC-to-5VDC converter "bug" inside a false outlet box

Depending on the location of the dead drop, this could be concealed within a false junction box that would be plugged in over the top of a standard 2-outlet 120V AC. If— in the spirit of the original USB dead drop— you wanted to embed the card in a brick wall, then the device could be powered from a USB powerbank.

The outlet shown from the front, showing how the WiFi SD card is completely hidden

The outlet sits out noticeably from from the wall; but it can be easily placed over an existing outlet while completely hiding the contained SD card server.

I named the project warTOR for "wireless anonymous repo" + TOR. Though it's not connected to the Tor network in any way, I thought this title captured the spirit of anonymity (plus I wanted to use some Pokémon sprites). If someone would like to try it, the Toshiba cards can be setup as a wireless bridge... from a Tor gateway?

Future Plans

Something else that I'd like to try is powering the card via a small solar cell, but I haven't gotten there yet... The greatest benefit of the wireless dead drop is that one could log into the WAP from their cellphone, upload or download a file, and no one could discern that any sort of exchange was happening. However, I'm also working on a clientside chat application that could be hosted on the cards.

With this implemented, then two people could sit down in a café and send messages back and forth over the private network; or, someone could login to the network and type out a message for the other person to see at a later date.

Screenshots of the warTOR server on a mobile device, with upload/download instructions and chat

Screenshots from the warTOR server on a mobile device. I used Toshiba's provided documentation to setup file upload/download, and started building a chat service that anyone in the vicinity can use to "drop" and read messages.

Here are some screenshots from the application 👆. I'll be doing a follow-up post with a GitHub link to the FlashAir CONFIG file that I'm using on my card. I'll also upload the source code for the original warTOR server with instructions on how you can deploy your own warTOR in the wild!

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