Banned Book Library | Rick's Blog

Banned Book Library

Tags = [<br>cyberpunk,<br>hacking,<br>hardware ]

Posted on June 15, 2026 at 06:35 PDT

Overview

A long while back I had an idea to hack a WiFi smart light bulb to do something more useful to me. Actually, I had a few different ideas of things to do with them. One of these ideas was to modify the device to have an open WiFi access point and a web server hosting banned books. The idea was that if you lived somewhere that banned books you thought were important, you could theoretically stick a digital copy of the book on one of these light bulbs. Then you could go install it somewhere in your community. As long as the light bulb is switched on, then anyone in the vicinity can still access the banned material assuming they have an electronic device with WiFi. Since the device is a light bulb, it would be difficult to detect and likely to go unnoticed. A cyberpunk digital dead drop. These devices are also fairly inexpensive, so leaving them around town as is hopefully not very cost prohibitive.

I think the idea hosting banned books specifically came to me after having read Ben Brown's short story Library. It's been a while since I read it, but if I recall there are characters in the story who maintain a "library" which acts as a digital archive of creative works, owners manuals, 3d models, etc. Things that others might find useful or interesting that you wouldn't want to lose should they be somehow wiped from the Internet. That's only a part of the story and it was a fun read. You should go read it!

Anyway, a few months ago I decided to finally get to work on this project. The result is the Banned Book Library!

Hardware

I brought up this idea with some folks at my local DEFCON meetup group. One of them had some experience with home automation and recommended I look into Tasmota. Tasmota is an open-source firmware you can install on various smart devices to integrate them into a home automation system such as HomeAssistant. The main idea with this firmware is to provide you with local control over the device. Many of these devices rely on cloud services that change over time or sometimes completely disappear, leaving the devices unusable. Tasmota allows you to untether yourself from these cloud services and host everything internally. Actually, this is another great parallel to Ben Brown's Library story. Also relevant is Cory Doctorow's Unauthorized Bread.

I hadn't heard of Tasmota but after reading about it, it sounded like a good way to go. I had sort of expected many of these smart light bulbs would rely on ESP32 chips, or similar. Having no experience with them made it feel a bit daunting to get started. I thought maybe it might be easier to modify the Tasmota firmware to do what I wanted instead of writing something from scratch. I did not end up modifying Tasmota in the end, but this rabbit hole did lead me to find a website that sells WiFi light bulbs with Tasmota pre-installed. The product page even specified that the bulb uses an ESP32C3 4MB. It also listed which GPIO pins were used to control the various LEDs, which would come in handy later:

R：GPIO6<br>G：GPIO7<br>B：GPIO5<br>CW：GPIO3<br>WW：GPIO4

This seemed like a great starting point because although Tasmota supports many other devices, not all of them can be flashed over the air (OTA). Many of them require breaking them open, soldering on small wires, and flashing via a serial programmer. Tasmota has a built-in mechanism to update the firmware OTA, so it seemed likely I might be able to flash my own modified Tasmota firmware, or otherwise a custom firmware without having to tear the light bulbs apart.

The one thing that struck me as a potential problem was the flash size. It was listed as 4MB. This is not very much space to host a library of books... That 4MB would need to fit all of the firmware, the website, and any books. Not much space. I thought I might be able to overcome this by adding storage, such as a microSD card reader. More on that later.

I purchased two of these bulbs to play with. I figured I might end up breaking or bricking one, so having a backup would be good.

Teardown

The bulbs showed up in the main a few days later and I opened up the box to check it out.

The first thing I wanted to do was open it up and see what I was working with. I was mainly wondering if the pins were exposed so I might be able to attach a microSD card reader. To remove the white plastic bulb on top, I ran a razer blade around the circumference of the bulb in between the base and the bulb. I had to go around twice, the second time angling the knife downward to cut through the sealant inside. Then I was able to just twist and pull the bulb right off. Minimal damage.

This revealed a round daughter board with all of the LEDs on it. This PCB was attached to another one underneath using six pins. There was also a hole in the middle where the mother board stuck through a bit. This ended up being the antenna for the...