What is this?

This is a simple app that cryptographically splits a BIP39-compatible seed phrase into multiple key pairs using one-time pad encryption.

Why?

This allows you to split the seed phrase into 3 fragments that can be stored separately. You will only need 2 of the fragments to reconstruct the original seed phrase. A single fragment contains no information about the other fragments and would not help an attacker in brute-forcing the encryption.

This app is written in vanilla JS, has 0 external dependencies, and is designed to work offline or in an air-gapped environment.

Caution

I am not responsible for lost, stolen, or otherwise compromised seed phrases or encrypted keys. I make no guarantees to the effectiveness of the encryption/decryption or the results.

Always test, backup, and consider using additional key splitting methods for extra security.

Usage instructions

1. Clone repo
2. Turn off your internet
3. Open index.html

Encrypting

1. Simply input a seed phrase into the top input to generate key pairs
2. You will see 4 keys: A1, A2, B1, and B2. This constitutes two pairs:
   1. A1 and B1
   2. A2 and B2

A complete pair is sufficient to decrypt the original seed phrase.

Storing keys

The keys should be stored in 3 fragments in separate locations, as follows:

• Fragment 1: A1, A2
• Fragment 2: A1, B2
• Fragment 3: B1, A2

This way, any 2 fragments will be able to construct a complete key pair.

Using a 2-out-of-3 authentication framework can accommodate:

• loss of a single fragment
• compromise of a single fragment

Decrypting instructions

1. Paste the two keys of a complete pair into the inputs on the bottom half of the app