Melanie Allen Wants to Bring Dead-Man Switches to All with a 3D-Printable BusKill Adapter

Designed for local production where a commercial cable might be subject to interception, this open-hardware device triggers with a yank.

Gareth Halfacree
1 month ago3D Printing / Security / HW101

Maker and security enthusiast Melanie Allen is looking to give anyone who wants one a dead-man switch capable of locking a computer — or erasing its data automatically — at the pull of a cable, using a 3D-printable version of the BusKill cable.

The BusKill project aimed to provide a functional dead-man switch for those who felt at risk of sudden and unexpected equipment seizure. Connected to a USB port, a BusKill cable need only be given a firm tug to disconnect its magnetic coupling and trigger the user's choice of security response — anything from locking the system until the user logs back in to erasing an encryption key to make its stored data inaccessible.

If you need to secure your devices in a second, this 3D-printable BusKill cable can help. (📹: Melanie Allen)

While you can buy commercial BusKill cables, ordering one comes with its own risks: if you are truly a target of state-level intelligence agencies, the chances are they could intercept the shipment and send you something that looks like a BusKill but isn't. The solution, then: make one yourself, which is exactly what BusKill volunteer Melanie Allen has been doing.

"The best way to confirm the integrity of your hardware is to build it yourself," Allen explains. "Fortunately, BusKill doesn't have any circuit boards, microcontrollers, or silicon; it's trivial to print your own BusKill cable — which is essentially a USB extension cable with a magnetic breakaway in the middle.

"Three years ago, [BusKill developer] Michael [Altfield] asked me if I was interested in developing a 3D-printed case for the magnetic breakaway," Allen explains. "On July 3, 2023, I successfully created a prototype of the magnetic release. [That version] had a connection that was too weak. I wasn’t sure if it was because of the magnetic strength of the disc magnets used or if it was something I could fix with a better design of the 3D printed 'faces.'"

Now on its third revision, Allen's design — created in OpenSCAD — completes its USB connection via pogo pins, with female and male USB connectors at either end. In the middle, the pogo pins complete the connection between the two halves of the 3D printed BusKill — and are held in place by magnets strong enough that it won't come undone unexpectedly but weak enough that a hard yank will split the adapter apart and trigger the BusKill software.

More details on the project are available on the BusKill website and on Allen's blog; the project's design files are available on the BusKill GitHub repository under the reciprocal GNU General Public License 3, with Allen currently working on a v3.1 update.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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