Banana Split 🍌 ·

Banana Split makes your paper backups more resilient and secure using Shamir’s secret sharing.

It splits your secret (e.g., paper backup) into N pieces, but only requires a majority of those pieces (N/2+1) to recover your secret.

Why Banana Split?

There’s a few problems with normal paper backups: If you have the whole paper backup somewhere, you’re vulnerable to someone finding it and stealing it—without you ever knowing they did (e.g., they can just take a photo of it). If you split your paper backup into two, what happens if one of those pieces goes missing?

For example:

You use Banana Split to split your paper backup into 5 pieces. You then give 5 friends a piece. It only takes 3 of those friends to come together to retrieve the paper backup. If 2 of your friends end up losing their piece, it’s okay. And if 2 of your friends collude and try to retrieve your backup, they won’t be able to. That is to say:

Any 3 friends will know everything; any 2 friends will know nothing.

Usage

How do you make a Banana Split?

1. Save the Banana Split HTML page and open it in offline mode.
2. Type your secret into Banana Split. Your secret will be encrypted with an auto-generated passphrase and split it into the number of QR codes you specify.
3. Print out your QR codes.
4. Write the passphrase by hand on every sheet. Doing this by hand protects against an attacker intercepting things you’re sending to the printer.

How do you retrieve a Banana Split?

Recovery can be done on any device with a webcam.

1. Save the Banana Split HTML page and open it in offline mode.
2. Using your webcam, scan in a majority of your QR code printouts (e.g., if you had 7 printouts, you’ll need 4).
3. Enter your passphrase.
4. Viola! Your secret is restored.

⚠️ Important

Work local and offline

Banana Split is a self-contained HTML page. To ensure your precious data is never sent outside, it only works when opened from your local hard drive while your browser is in Offline mode.

Without the passphrase, you won’t be able to retrieve your secret

To retrieve your secret, you’ll need to have a majority of the printouts and know the passphrase. This is why it is critical for you to write the passphrase on every printout.

Keep the HTML document

This HTML page is a fully self-contained application under GPLv3 license. Please feel free to copy and share it with anyone you want to use it. The more copies out there, the less likely it will be compromised or taken down.

Development

Project setup

yarn install

Compiles and hot-reloads for development

yarn run serve

Compiles and minifies for production

yarn run build

Run your tests

yarn run test:unit

Lints and fixes files

yarn run lint

Customize configuration

See Configuration Reference.