Adapting the Signal Protocol for P2P Messaging
⚠️ WARNING: This document is not finished. The details in this document are subject to change.
The Signal Protocol has become the gold standard for end-to-end encrypted messaging, powering applications like WhatsApp, Signal, and Facebook Messenger. But what happens when you want to implement the same level of security in a truly peer-to-peer environment—one without centralized servers managing pre-keys and message routing?
In this article, we'll explore how to adapt the Signal Protocol's X3DH (Extended Triple Diffie-Hellman) key agreement and Double Ratchet algorithm for direct peer-to-peer communication over WebRTC. We'll discuss the challenges unique to P2P environments, propose practical solutions, and walk through a browser-based JavaScript implementation that maintains the security guarantees of the original protocol.