Cahoots

Open hardware · open protocol

Get in cahoots.

Encryption keys you made in a room, with people you trust. Cahoots badges make a shared secret when you touch them together. Use that secret to protect your VPN, your files, and your group chat, including against computers that don't exist yet.

Try it in your browser How it works
  1. Clear cardCredit-card size, 3 mm thick. Clear because the chip's design is public, and so is everything around it.
  2. 1.54" e-paperAfter a ceremony, every badge shows the same six words. Read them out loud. If they match, you're in.
  3. Baochip-1xMakes real random numbers and keeps the secret on the chip. It destroys every piece after one use.
  4. Stack and snapCards stack. Magnets line them up, gold pads on the face meet spring fingers underneath, and the pile talks through them. No Wi-Fi, no Bluetooth.
  5. Coin cellA CR2016 runs it for a year or more. Nothing to charge. Never plugged in.

Scroll to see inside

Why

Most keys are made by math.
These are made by meeting.

Nothing to intercept, now or later

The badges make the secret when they touch. It was never sent, so there is nothing to capture today and nothing to decrypt later, quantum computer or not. The one step that uses math, badges sealing their parts to each other, uses X-Wing, a post-quantum scheme.

Made in the room. Quantum-safe by construction.

Works with what you already run

Plug the secret into WireGuard, your file encryption, or your group chat. They all have a slot for a shared secret. It usually sits empty, because sharing one safely was the hard part. Now it isn't.

An attacker has to beat the math and get into the room.

Used once, then gone

The badge uses each piece of the secret once, then wipes it. Keys rotate on their own, with no server in the middle. If a badge is lost, what it already protected stays protected.

Short messages get true one-time-pad protection. No computer, now or later, can break them.

WireGuardHPKEageTLS 1.3MLSMeshtasticSSH

How it works

Five minutes, in person.

  1. Start a cahoot. One person names the group and says how many people are in it. Every badge shows the details. Everyone confirms.
  2. Draw. Each badge makes its own random numbers and locks them in before seeing anyone else's. Nobody can cheat after the fact.
  3. Touch. Badges stack into a pile and pass their numbers up and down it until everyone has all of them.
  4. Mix. Every badge combines all the numbers into one shared secret. If even one person was honest, the secret is random.
  5. Say the words. Six words appear on every screen. Read them out loud. If they match, you're in cahoots. If not, start over.
sf-meetupTRNG · T4
sunsetvalvepresentravencurtainpudding
read aloud · press to confirm

Hardware

Build your own, or get ours.

It runs on a phone with no hardware at all, on any dev board, or on the badge we make. A group is only as safe as its least safe device, and the badges tell you which one that is before you commit.

T0PhoneNo hardware needed. The phone decides how well secrets are wiped.
T1Any microcontrollerWipes secrets for real. A stolen board still gives up its secret.
T2SealedLocked firmware and encrypted storage. A copied chip is useless without the PIN.
T3Key storeThe chip guards the secret itself. Too many wrong PINs and it wipes everything.
T4InspectedSomeone has looked at the chip under a microscope and matched it to the public design. This is the badge we make.

The feed

Post anywhere. Only your circle can read it.

During the Cold War, radio stations read out strings of numbers. Anyone could listen. Only the spy with the matching code sheet could understand.

Cahoots works the same way. Messages go on a public feed, scrambled. Anyone can see them. Only your circle can read them or post as you. Not even the people who run the feed can. The feed keeps everything in order and can't be quietly rewritten.

circle 6f8648f8seq 41 · 25 B

    

  






  
Build

  
Four parts make a badge.

  

    
Randomness
A real random number source that checks itself. If the check fails, the ceremony stops.

    
Storage
Memory the badge controls directly, so a wipe is a real wipe. The badge reads every erase back to prove it.

    
Screen and link
A screen that shows six words, and a wire to the next badge. The code is open, and a simulator on your laptop stands in for the hardware.

  

  

    Source on GitHub
    Read the protocol 
    What people use it for