# X3DH https://signal.org/docs/specifications/x3dh/ https://signal.org/docs/specifications/x3dh/x3dh.pdf Links: [[Signal]], [[Signal Protocol]] By [[Moxie Marlinspike]], [[Trevor Perrin]] *This document describes the "X3DH" (or "Extended Triple Diffie-Hellman") key agreement protocol. X3DH establishes a shared secret key between two parties who mutually authenticate each other based on public keys. X3DH provides forward secrecy and cryptographic deniability.* *X3DH is designed for asynchronous settings where one user ("Bob") is offline but has published some information to a server. Another user ("Alice") wants to use that information to send encrypted data to Bob, and also establish a shared secret key for future communication.*