We’re happy to announce that we’ve had good progress on the design of the 3D printable BusKill USB-A magnetic breakaway couplers this year!

While we do what we can to allow at-risk folks to purchase BusKill cables anonymously, there is always the risk of interdiction.

We don’t consider hologram stickers or tamper-evident tape/crisps/glitter to be sufficient solutions to supply-chain security. Rather, the solution to these attacks is to build open-source, disassembleable, and easily inspectable hardware whose integrity can be validated without damaging the device and without sophisticated technology.

Actually, the best way to confirm the integrity of your hardware is to build it yourself. Fortunately, printing your own circuit boards, microcontroller, or silicon has a steeper learning curve than a BusKill cable — which is essentially just a USB extension cable with a magnetic breakaway in the middle.

Mitigating interdiction via 3D printing is one of many reasons that Melanie Allen has been diligently working on prototyping a 3D-printable BusKill cable this year. In this article, we hope to showcase her progress and provide you some OpenSCAD and .stl files so you can experiment with building your own and help test and improve our designs.

ⓘ Note: This post is adapted from its original article on Melanie Allen’s blog.

Developing the Prototype

Ideation

A few years ago, Michael asked me if I was interested in developing a 3D-printed case for the magnetic breakaway. He enumerated the following design requirements:

• The case should be as small as possible, because it shouldn’t block neighboring ports, nor sit heavy in the port causing it to bump into objects on the desk.
• The case should be able to be dissembled, so that people can make sure it isn’t tampered with. It shouldn’t be glued together.
• In order to avoid using glue, we had a factory specially manufacture some hexagonal shaped magnets that we believed would be able to sit inside the printed part without glue.
• Much like USB breakaways that are designed to prevent wear and tear on ports, the case would house a pogo pins and magnets, and a USB.

However, over the past years’ iterations, we adjusted the requirements:

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