For the last 2 years the Matrix.org team has been working on libolm - a clean-room FOSS liberal-licensed (Apache) independent specification andimplementation of the end-to-end encryption Double Ratchet Algorithm aspopularised by Signal, WhatsApp, Facebook Messenger, Google Allo etc. As ofNovember 2016 the spec and library is finally finished and being unleashed onthe world, successfully audited by NCC Group, and is available as part ofMatrix's client SDKs for Web, iOS & Android and apps that use them (e.g.Riot.im). In this talk we will discuss Matrix's mission to be an open, global end-to-end-encrypted communications network - showing that it's possible to buildopen communication infrastructure which is both secure _and_ decentralised(unlike the silos of Signal, Wire, etc); where users can own their data andpick who they trust to run their service. We'll show how you can use Matrix tosecurely defragment communities scattered over proprietary silos such asSlack, Telegram and Gitter, open silos like Rocket.Chat and MatterMost -whilst also bridging to IRC, XMPP and even SIP. We'll also introduce the Megolm cryptographic ratchet - a new ratchet writtenby Matrix to tackle the specific problem of encrypting Matrix rooms, which mayhave thousands of users and require synchronised history over multiple devices(including new devices). Megolm is layered on top of the Olm ratchet, and isunusual in that it encrypts per-device rather than per-user, and lets roomsspecify how much scrollback may be decrypted by new devices: providing acustomisable trade-off between privacy and usability. This is a major stepforwards from other systems which unilaterally prioritise privacy overusability. Finally, we'll give a quick tour of all the FOSS clients, bots and bridgesthat the community has built on Matrix over the last year - ranging fromnative Qt clients (Quaternion, NaChat, Tensor), CLI apps (WeeChat), Reactwebapps (Riot, Freebird) to Native mobile apps (Riot). Matrix.org is a non-profit open source initiative dedicated to creating andmaintaining the Matrix open standard for decentralised communication, whosegoal is to create an open and secure ecosystem for interoperable messaging,VoIP and IoT communication on the internet.