stoneburner / DoubleRatchet

Implementation of the Double Ratchet protocol in Swift based on libsodium.

DoubleRatchet

Implementation of the Double Ratchet protocol in Swift. The cryptographic operations are provided by libsodium entirely.

Usage

Alice and Bob calculate a shared secret using a secure channel. After that one party can start the conversation as soon as she gets to know the public key of the other one.

import DoubleRatchet

let sharedSecret: Bytes = ...
let info = "DoubleRatchetExample"

let bob = try DoubleRatchet(remotePublicKey: nil, sharedSecret: sharedSecret, maxSkip: 20, maxCache: 20, info: info)

// Bob sends his public key to Alice using another channel
// sendToAlice(bob.publicKey)

let alice = try DoubleRatchet(remotePublicKey: bob.publicKey, sharedSecret: sharedSecret, maxSkip: 20, maxCache: 20, info: info)

// Now the conversation begins
let message = "Hello, Bob!".bytes
let encryptedMessage = try alice.encrypt(plaintext: message)
let decryptedMessage = try bob.decrypt(message: encryptedMessage)

print(decryptedMessage.utf8String!) // Hello, Bob!