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3D Printable BusKill Prototypes
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3D Printable BusKill Prototypes

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!

3D Printable BusKill (2023.04)

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

Screenshot of a GitHub Issue
The original issue posted in GitHub


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.
Photo of the design on a napkin
Napkin drawing, when you know its serious

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

  • We learned that we didn’t have to put the magnetic release near the port, but that it is better to put it near the person.
  • We realized that these parts are so small (and magnetic), and the magnets so strong, that assembly requires glue. The case itself doen't require glue, but the pogo pins and magnets must be glued in place.
  • Because we are now ok with having to use glue, it is probably better to use easy to find disc magnets rather than the special hexagonal ones.
  • The case doesn’t actually need to house the USB, only the pogo receptors, pogo pins, wires, magnets, and cord.

This process taught me about the realities of going from idea to execution.

My Journey with OpenSCAD

Photo of various 3D printed BusKill prototypes
Pile of test prints of various iterations of the project

When I started this project, I was novice-beginner level with OpenSCAD. I had designed something of similar complexity about 8 years ago. It was a model of an assembly related to creating a timelapse camera for Raspberry PI. I discovered that I had a lot to learn about actually writing good, parametric OpenSCAD code... Even though I commented my BusKill OpenSCAD code thoroughly, it was a mess! It was hard to use myself, let alone sharing with the open source community...

Screenshot shows a 3D model of a 3D Printable BusKill in OpenSCAD
OpenSCAD, the tool I used to design the release case

I had to rewrite it all... sometimes you have to break things to fix them. You have to go backwards to go forwards.

Prototype Begins

And so, chipping away whenever I could -- whether it was few minutes or a few hours -- I am now working on the PROOF OF CONCEPT / 1st Prototype.

And that's what I'm here to share with you today. However, it's still very much a work-in-progress (more on this below).

Current Design

The current prototype design of the 3D printable magnetic breakaway coupler consists of two sides, each of which consist of a top, middle, and bottom. In the OpenSCAD code, the side that would stay with the laptop is called the "release" and the side that would stay with the person is called the "breakaway".

Animated GIF Image shows the explosion of the bottom, middle, and top of the BusKill model in CAD
Both sides of the 3D Printable BusKill coupler have 3 pieces

Tools Used:

Wire stripper, soldering iron with fine tip, helping hands, xacto knife, painters tape, multimeter, alligator clips

Materials Used:

3D printed case (6 pieces), 8 magnets, 4 pogo pins, 4 pogo receptors, solder, wire, usb-to-usb-port cord, usb, carabiner, E360 glue

⚠ WARNING: Many materials used are hazardous, please follow the safety labels if you do this at home. Use proper ventilation, skin, eye, and lung protection when required.

Note: If you can’t acquire a usb-to-usb-port cord, it’s possible to make your own as long as you have a spare usb-to-usb cord and a spare charger that you don’t mind dissembling for this purpose. However, it’s important to make sure that the cord is a data cord, and not a charging cord only. You’ll know because data cords have 4 wires whereas charging-only cords have two wires.

Photo of the 3D printed BusKill
Fresh print of bottom, top, and middle

Print the Case

  1. This prototype uses magnetic_release_B_v0.9.stl. Download from the Github Repository: https://github.com/BusKill/usb-a-magnetic-breakaway
  2. I have a Flashforge Creator Pro and use the Flashforge slicer. I print Hyper Quality and using a raft. Takes about 45 minutes.

ⓘ Note: If you'd prefer to buy a BusKill cable than make your own, you can buy one fully assembled here.

Photo of a USB-A Extension Cable cut in half and stripped
Splice the USB Extension Cable

Assemble the cable

Step 1:

Cut near the port. Splice the wires. Note: cut somewhat close to where the USB attaches to the cord, but not so close that you don't have room for error.

Step 2:

Glue magnets to the middle piece:

  1. Arrange magnets in place Optional: mark the tops and bottoms of the magnet with permanent marker
  2. Apply glue to the middle piece
  3. Slide in the middle piece for one side.
  4. Slide in the middle piece for the other side.
  5. Use a thin but firm material to carefully separate the pieces and allow glue to set.

Tip: I put down a little blue painter’s tape on my workspace where I want to put my pieces down to dry. Also, there’s very little room for plastic-out-of-place and 3D printers don’t always print perfectly. If your magnets aren’t sitting securely, there may be a bit of plastic blocking the way that you need to trim out.

Step 3:

Photo of the pogo pins being soldered to wires
Soldering pogo pins
  1. Solder USB wires to pogo pins
  2. Solder USB wires to pogo receptors

Note: There is a slight asymmetry in the design, you’ll notice a thicker side and a thinner side. This can help you identify if the "top" and "bottom" pieces are oriented correctly.

Tip: I find the original USB wires so tiny and unwieldy that it's difficult to solder them to the even pogos... so I spliced them into breadboard wire first.

Diagram showing the pinout of USB
Pinout diagram I used

Step 4:

  1. Consult pinout diagram to arrange wires correctly.
  2. Use marker to label wire channels in the printed piece.

Step 5:

Glue wires carefully to the top and bottom parts of the case.

The spring part of the pogo pins when pressed should be flushed with the edge of the case, but when not pressed should poke out.

Step 6:

When the glue is dry, sandwich the middle piece between the top and bottom pieces and wrap securely with electrical tape.

NOTE: In the image below the wires are not actually glued yet. I was just sort of mocking it up.

Photo of half of the 3D printed and assembled BusKill coupler
Dry Fit

Where We Are Now

Photo of the spliced BusKill cable connectivity test
Testing the spliced BusKill cable

Before I glued the wires in, I wanted to make sure everything was working and wired correctly.

So I dissembled and attached each wire to itself with alligator clips to test whether my computer would detect it. It failed.

It seemed to me that if this didn’t work then if I proceeded onward it was likely not going to work. I’m a little perplexed. I tried continuity testing, but I'm not sure if my multimeter is faulty..

So I started over again with splicing the cables ... even though I was confident in my soldering work. Yet even without any wires spliced-in ... the wire connected to itself with the alligator clips still isn’t functional. So what is the problem here?

If you have access to a 3D Printer, you have basic EE experience, or you'd like to help us test our 3D printable BusKill prototype, please let us know. The whole is greater than the sum of its parts, and we're eager to finish-off this 3D printable BusKill prototype to help make this security-critical tool accessible to more people world-wide!

If you'd like to purchase a BusKill cable, click here.

Bitcoin Black Friday (10% discount on BusKill)

In celebration of Bitcoin Black Friday 2022, we're offering a 10% discount on all BusKill cables sold between Nov 19 to Dec 04.

BusKill Bitcoin Black Friday Sale - Our Dead Man Switch Magnetic USB Brakaway cables are 10% off all orders paid with cryptocurrency

What is BusKill?

BusKill is a laptop kill-cord. It's a USB cable with a magnetic breakaway that you attach to your body and connect to your computer.

If the connection between you to your computer is severed, then your device will lock, shutdown, or shred its encryption keys -- thus keeping your encrypted data safe from thieves that steal your device.

What is Bitcoin Black Friday?

Black Friday is ~1 month before Christmas, and it's the busiest shopping day in the US. The first "Bitcoin Friday" (launched by Jon Holmquist) was Nov 9th, 2012 (at the time, one bitcoin was ~$11). The following year, the two ideas merged to become Bitcoin Black Friday.

This year, we're joining Bitcoin Black Friday by offering our products at a 10% discount if you pay with cryptocurrency.

Why should I use cryptocurrencies?

We've always accepted cryptocurrencies because:

  1. They're more secure than pre-cryptocurrency payment methods
  2. They're a more egalitarian system than pre-cryptocurrency finance
  3. They're more environmentally friendly than pre-cryptocurrency financial systems
  4. The fees are less than pre-cryptocurrency transactions
  5. They allow for anonymous purchases online
  6. Their transactions are censorship-resistant


Before cryptocurrencies, making an online transaction was horrendously insecure and backwards.

Diagram shows all the third parties that can steal your funds in a pull-based system: Merchant, Acquierer, Payment Processor, Switch, Issuer
"Conceptually, pull-based transactions are really not that different than giving three parties the password to your online banking service and trusting them to log in and take what they need. You have to trust the merchant, their IT supplier; the acquiring bank, their third-party processor; the card network; and your own card issuer—and everybody who works for them and has access to their systems. If a bad guy gets hold of your card details at any point in this process, they could drain your account.
The picture shows the scope of all the entities with access to your critical card information" source

Asymmetric cryptography has been available since the 1970s, but CNP (Card Not Present) transactions to this day still don't use public keys to sign transactions. Rather, you give your private keys (that is, your credit card number, expiry, etc) directly to the merchant and you authorize them to pull money out of your account (trusting that they take the right amount and not to loose those precious credentials).

Bitcoin flipped this around to actually make transactions secure. With bitcoin, you don't give others the keys to take money out of your account. Instead, transactions are push-based. You sign a transaction with your private keys, and those keys are shared with no-one.

Even today, pre-cryptocurrency transactions are abhorrently insecure. In the US or Europe, if someone knows your account number and bank, they can direct debit money out of your account. For the same reason, losses due to credit card theft is enormous. To quote Satoshi Nakamoto's criticism of pre-cryptocurrency transactions, "A certain percentage of fraud is accepted as unavoidable"

In fact, fraudulent transactions in the banking industry are so common that your bank will generally reimburse your account for any malicious transactions that you tell them about within 60-90 days. But if someone drains your account of all your money and you don't notice for 12 months? Too bad. All your money is gone.

Graphic shows a push-based model where a consumer pushes value directly to a merchant
In Bitcoin, transactions are push-based. source

Tokenization and 3DS are merely bandages on a fundamentally backwards, pull-based transaction model.

But because bitcoin is push-based, it's magnitudes more secure.


If you have a bank account, then you probably take a lot of things for granted.

Like buying things online (with a credit card). Or getting cash when traveling abroad (from an ATM machine). Or taking out a loan so you can start a business.

Before crypto-currencies, it was very difficult to do these things unless you had a bank account. And in 2008 (the year with the first-ever bitcoin transaction), McKinsey & Company published a report concluding that half of the world's adult population is unbanked.

But with crypto-currencies, anyone with access to the internet and a computer or smart phone can use bitcoin to send and receive money online -- without needing to first obtain a bank account.


The energy required to facilitate transactions in decentralized, blockchain-based cryptocurrencies like bitcoin is minuscule by comparison. And, most importantly, the amount of energy used to solve the proof-of-work problem does not grow as the number of transactions-per-second grows.

Traditional financial institutions require an enormous amount of overhead to facilitate transactions in their centralized networks. Unlike bitcoin, which was designed specifically to eliminate the unnecessary overhead created by a trusted third party, pre-cryptocurrency transactions required humans to verify transactions. These humans require office buildings. These office buildings require energy to build and maintain. And, most importantly, as the number of transactions-per-second grows on their network, the number of humans and office space also grows.

Bar Graph shows the comparison of energy usage of Bitcoin and various industries.
Bitcoin versus other industries — yearly energy use, in TWh source

This fact is often misunderstood because there's a lot of misinformation on the Internet that makes a few disingenuous modifications to the facts:

  1. They calculate the energy usage of the computers processing transactions only, maliciously omitting calculating the energy usage of the entire industry's infrastructure (eg energy used by office buildings)
  2. They calculate the energy usage per transaction, maliciously omitting the fact that the amount of energy expended by bitcoin miners is automatically adjusted by the proof-of-work algorithm (so energy usage does not increase as the network scales-up)
  3. They offer statistics about "energy usage" without mentioning the energy sources. It matters if the energy source is coal/nuclear/natural-gas or solar/wind/hydroelectric

Nic Carter Headshot
...estimates for what percentage of Bitcoin mining uses renewable energy vary widely. In December 2019, one report suggested that 73% of Bitcoin’s energy consumption was carbon neutral, largely due to the abundance of hydro power in major mining hubs such as Southwest China and Scandinavia. On the other hand, the CCAF estimated in September 2020 that the figure is closer to 39%. But even if the lower number is correct, that’s still almost twice as much [renewable energy sources] as the U.S. grid

-Nic Carter, Harvard Business Review

The facts are that the energy usage of bitcoin is magnitudes less than the energy used by pre-cryptocurrency financial intuitions, that energy usage does not increase as the number of transactions processed by the network increases, and that mining bitcoin is often done with renewable energy.

Low Fees

The introduction to the Bitcoin White Paper (2008) clearly states that Bitcoin was created to reduce costs by using a distributed ledger (the blockchain) to eliminate the need for a trusted third party.

A hooded figure wearing a guy faux ask sits in lotus pose. Behind them is an illuminated personification of Bitcoin
Satoshi Nakamoto, anonymous Bitcoin inventor

Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model.
Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs
These costs and payment uncertainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party.

What is needed is an electronic payment system based on cryptographic proof instead of trust,
allowing any two willing parties to transact directly with each other without the need for a trusted third party. Transactions that are computationally impractical to reverse would protect sellers from fraud, and routine escrow mechanisms could easily be implemented to protect buyers. In this paper, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp server to generate computational proof of the chronological order of transactions.

-Satoshi Nakamoto, Author of Bitcoin: A Peer-to-Peer Electronic Cash System

At the time of writing, the average transaction fee for a bitcoin transaction is $0.06. And unlike pre-cryptocurrency transactions, you can increase or decrease the fee that you pay to increase or decrease the time it takes for the transaction to complete (at $0.06, it will get added to the blockchain in ~1 hour).

By comparison, the way to send funds internationally through the Internet via pre-cryptocurrency banks is via an international wire transfer. Fees very per bank, but they typically charge $15-$85 per transaction. And unlike bitcoin, wire transfers won't make move on nights and weekends, so they can take 1-7 days to complete.

Also, with bitcoin, that $0.06 transaction fee only applies when you're sending money. Many banks will also charge a fee for an incoming wire transfer. In bitcoin, there is no transaction fee to receive money.


Though early cryptocurrencies like Bitcoin don't ensure anonymity like newer privacy coins, ZCash and Monero were designed specifically to provide private transactions.

This allows our customers to purchase from us anonymously, which can be extremely important for activists and journalists whose lives are threatened by their adversaries.

Tweet from WikiLeaks that reads "WikiLeaks now accepts anonymous Bitcoin donations on 1HB5XMLmzFVj8ALj6mfBsbifRoD4miY36v"
WikiLeaks started accepting donations in Bitcoin 7 months after PayPal froze their account

We accept both ZCash and Monero. If you'd like us to accept another privacy coin, please contact us 🙂


Cryptocurrencies like bitcoin are peer-to-peer and permissionless. Transactions exchanging bitcoins occur directly between two parties. There is no middle-man that has the power to block, freeze, or reverse transactions.

Before blockchains were used to maintain a public ledger and enable peer-to-peer transactions, we were dependent on big financial institutions to move money on our behalf through the internet. That antiquated system allowed them to censor transactions, such as donations made to media outlets reporting war crimes and donations to protest movements.

Evan Grer portrait
"For me, that is one of the coolest things about bitcoin"
"People can potentially use it donate more anonymously to dissident groups and causes in a world where mass government surveillance threatens freedom of expression and certainly harms activists’ ability to fundraise for their work, when people are afraid they could be targeted by a government for donating to a worthy cause."

-Evan Greer, Director of Fight for the Future


After PayPal froze WikiLeaks's donation account in 2010, WikiLeaks started accepting bicoin in 2011.

From Occupy Wall Street to Ukraine, defenders of democracy have utilized permissionless cryptocurrencies to accept international donations without the risk of transactions made through financial institutions.

Buy BusKill with crypto

Don't risk loosing your crypto to a thief that steals your laptop. Get your own BusKill Cable today!

You can also buy a BusKill cable with bitcoin, monero, and other altcoins from our BusKill Store's .onion site

Bitcoin Accepted Here

Monero Accepted Here

To be notified about future sales of the BusKill cable, you can signup for our newsletter.

BusKill Now Shipping!

We're excited to announce that our first production run of BusKill cables is now in-stock in our distribution center. Existing orders are going out now, and new orders will ship immediately.

[BusKill] Our Dead Man Switch Magnetic Breakaway cables are Now Shipping!

The first BusKill prototype was born in 2017. It gained international popularity in 2020 when Michael Altfield described how to build your own BusKill cable. After extensive effort and with the help of several contributors, a Linux hacker's DIY cable got a user-friendly, cross-platform GUI.

When the only USB-A magnetic breakaway coupler on the market became out of stock and EOL'd, we raised $18,507 on CrowdSupply in early 2022 to manufacture our own injection-molded cable. One thousand logistics challenges later, Mouser started shipping BusKill cables to our backers in October 2022.

The assembled BusKill cable is plugged-into the USB-A port of a laptop

Now that the hardware is out the door, we're hard at work on new features for the BusKill app. Our top goal is to add a soft-shutdown trigger to the existing lock-screen trigger. At the time of writing, this is functional on Linux and Windows. We're just working out the kinks of privilege escalation on MacOS.

To be notified when we've added the soft-shutdown trigger to the BusKill app, you can signup for our newsletter.

We did our best to test BusKill across the three target platforms, but the wide spread of OS versions does leave room for error. If you happen to find a bug with BusKill, please let us know.

If you don't have a BusKill cable yet, you can buy one here on this website or build your own. And for the makers out there, checkout the progress on our 3D printable BusKill magnetic breakaway coupler 🙂

You can also buy a BusKill cable with bitcoin, monero, and other altcoins directly from our BusKill Store

Bitcoin Accepted Here

Monero Accepted Here

BusKill Demos (Windows, MacOS, Linux, TAILS, QubesOS)

BusKill Demo #2

Transparency is important. As we launch our crowdfunding campaign (making the BusKill cable available for purchase for the first time), we wanted to provide a clear video demo showing the cable in-use in all tested platforms:

Full Video Demo

Watch the below video to see a demonstration of BusKill running on all of the above-listed systems.


BusKill was tested to work in Windows 10.

Visit docs.buskill.in for instructions on how you can build your own BusKill cable and download the BusKill app for Windows.

Or you can buy a BusKill kit with the BusKill Windows app pre-installed on the the included USB drive.


BusKill was tested to work in MacOS 10.15 (Catalina).

Visit docs.buskill.in for instructions on how you can build your own BusKill cable and download the MacOS .dmg release.

Or you can buy a BusKill kit with the BusKill MacOS app pre-installed on the the included USB drive.


BusKill was tested to work in Ubuntu Linux.

Visit docs.buskill.in for instructions on how you can build your own BusKill cable and download the Linux .AppImage release.

Or you can buy a BusKill kit with the BusKill Linux app pre-installed on the the included USB drive.


BusKill was tested to work with TAILS (The Amnesic Incognito Live System).

While you could use the BusKill Linux .AppImage release with a second USB drive while using TAILS, the recommended solution for security-critical users is to just use the BusKill cable in-line with the TAILS live USB drive. This takes advantage of

  1. The BusKill cable's magnetic breakaway along with
  2. The TAILS built-in emergency shutdown

Visit docs.buskill.in for instructions on how you can build your own BusKill cable to use with TAILS.

Or you can buy a BusKill cable to support the BusKill project.


BusKill was also tested to work with QubesOS.

Due to the design of QubesOS (dom0, sys-usb, etc), the BusKill GUI app does not support QubesOS. Instead, QubesOS support is implemented using the qubes-rpc and a set of scripts stored in sys-usb and dom0.

For more information on how to use BusKill in QubesOS, see our BusKill guide for QubesOS.

Visit docs.buskill.in for instructions on how you can build your own BusKill cable to use with QubesOS.

Or you can buy a BusKill cable to support the BusKill project.

Quicker Emergency Shutdown for TAILS

Are you a security researcher, journalist, or intelligence operative that works in TAILS--exploiting TAILS' brilliant incognito & amnesic design that forces all of your network traffic through the Tor anonymity network? Great! This post is for you.

TAILS: The most secure OS available

TAILS is amnesic; it's designed to leave no trace of the fact that it was used on your laptop. But what if someone literally steals your laptop while you're working with classified information in TAILS? Not only will they get access to all of the tabs open in your Tor Browser (gaining access to your accounts for any sites you're currently logged into, gaining the ability to impersonate and send messages as you, etc), but they'd also be able to access the contents of your decrypted persistent drive!

Let's say you're a journalist, activist, whistleblower or a human rights worker in an oppressive regime. Or an intelligence operative behind enemy lines doing research or preparing a top-secret document behind a locked door. What do you do to protect your data, sources, or assets when the secret police suddenly batter down your door? How quickly can you actually act to shutdown your laptop and shred your RAM and/or persistent volume?

What if you had a magnetic trip-wire tied from your body to your laptop such that it would trigger the TAILS emergency shutdown if the cable got disconnected by you jumping to your feet or falling off your chair at the sudden bang of your front door being reduced to splinters?

Using a BusKill cable with your TAILS drive can help shave off those precious seconds needed to trigger an emergency shutdown that will help keep you, your data, and your contacts safe.

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