This is a mostly complete implementation of the Encrypted Header variant of the The Double Ratchet Algorithm designed by Open Whisper Systems.

WARNING: This implementation was created for learning purposes and should not be used outside of a development environment. Any concerns or suggestions are very welcome.

This implementation was built using the NodeJS crypto library as its only dependency. I decided to do this as Electron is the intended usage. However, it would be trivial to abstract the crypto provider in order to make this library browser friendly.

const Ratchet = require('doubleratchet').Ratchet

const pskRoot        = ... // a shared secret between alice and bob
const pskHeader      = ... // a shared secret between alice and bob
const pskNextHeader  = ... // a shared secret between alice and bob

const alice = new Ratchet(pskRoot, pskHeader, pskNextHeader)
const bob = new Ratchet(pskRoot, pskNextHeader, pskHeader)

alice.acceptHandshake( bob.makeHandshake() )

bob.decrypt( alice.encrypt('hello bob') )   // "hello bob"
alice.decrypt( bob.encrypt('hello alice') ) // "hello alice"

See examples directory for more.

git clone https://github.com/jowy/doubleratchet.git
cd doubleratchet
yarn install
yarn build

• flow typing
• comments
• tests
• clean up KDF flow
• clean up Key and CipherKey initialization and handling
• clean up buffer handling
• state (de)serialization
• fix header & nextHeader initialization and flow
• proper handling of input & output encoding
• revise CipherKey kdf
• error handling for various things
• throw properly typed errors
• rollback chain state on failure
• more examples demonstrating various features of the protocol
• API outline