A Ruby implementation of The Double Ratchet Algorithm.

This repository also includes the header encryption variant of the Double Ratchet.

This application is written in very small Ruby code. If you want to implement The Double Ratchet Algorithm in your preferred programming language, it is better to look directly at the Ruby code.

Usage

bundle install
bundle exec ruby double_ratchet.rb

Or

require_relative 'double_ratchet'

AD = ['00' * 64].pack('H*')
SK = ['00' * 32].pack('H*')
SIGNED_PREKEY = RbNaCl::PrivateKey.generate

HEADER_ENCRYPTION_FLAG = true

alice = Person.new
alice.init_x3dh_initiator(SK, SIGNED_PREKEY.public_key, AD)
alice.init_ratchet_sender(HEADER_ENCRYPTION_FLAG)

bob = Person.new
bob.init_x3dh_responder(SK, SIGNED_PREKEY, SIGNED_PREKEY.public_key, AD)
bob.init_ratchet_recipient(HEADER_ENCRYPTION_FLAG)

# Step 1
a1 = alice.send_message('A1')
puts bob.receive_message(*a1)

# Step 2
b1 = bob.send_message('B1')
puts alice.receive_message(*b1)

# Step 3
a2 = alice.send_message('A2')
b2 = bob.send_message('B2')
puts alice.receive_message(*b2)
puts bob.receive_message(*a2)
a3 = alice.send_message('A3')
a4 = alice.send_message('A4')
puts bob.receive_message(*a3)
puts bob.receive_message(*a4)

# Step 4
b3 = bob.send_message('B3')
b4 = bob.send_message('B4')
puts alice.receive_message(*b3)
puts alice.receive_message(*b4)
a5 = alice.send_message('A5')
puts bob.receive_message(*a5)

Documentation

https://signal.org/docs/specifications/doubleratchet/