Split a password into 5 blocks

Any 3 blocks bring your password back. 1 or 2 blocks reveal nothing at all. Ideal for a Bitcoin private key, a seed phrase or a master password.

  1. 1Enter your password. It never leaves this device.
  2. 2Print your 5 blocks, cut them out and give each to someone you trust.
  3. 3Any 3 blocks together reveal the password again.

Everything happens on this device. Nothing is sent to us.

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For the geeks: how secure is it?

It uses Shamir's method over GF(256), the same maths hardware wallets use to back up keys. Any 3 blocks rebuild the password. With only 2, every possible password is equally likely, so they give away nothing at all. That's a mathematical guarantee, not a promise.

Each block carries a checksum, so a typo or a misread QR code is caught straight away, and a fingerprint of your password is sealed inside so the result is always exactly right or an error. Before you see your blocks, all 10 combinations of 3 are tested. Everything runs on your device; the QR codes hold a link with the block after the #, which never reaches our server.

The method is public, and the recovery kit lets anyone rebuild a password without us.