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After a few months of silence, we are picking up work on OpenMLS again! 🎉 Phoenix R&D and Cryspen join forces to bring OpenMLS closer to v1.0. The MLS protocol draft is in the IETF working group’s last call and is thus on track to become an RFC soon. We want to make sure that OpenMLS is ready for wider adoption by the time the RFC is ready. To achieve this we start by catching up with all the changes to the protocol (up to the current draft-16), improving test coverage of the code, and working towards a more comprehensive test framework for interoperability. ...

Today, we are excited to announce the release of v0.4 of OpenMLS! 🎉 Some time has passed since we wrote about our roadmap to v0.4. In this post, we want to provide some insight into what has happened in the development of OpenMLS generally, but also relative to the goals we included in the roadmap. Our high-level goal with v0.4 was to reach a state where we have an API stable enough and an implementation robust enough such that people interested in OpenMLS can start exploring it in the context of their own projects. However, this is not v1.0 and we can neither promise that the API won’t change in the future, nor do we advise using OpenMLS in production or indeed in any security-sensitive context. With this disclaimer out of the way, let’s see what has happened in these past months. ...

It’s time for another update on OpenMLS because many things are happening behind the scenes. Today we are excited to announce a public roadmap for OpenMLS v0.4. This will not even be close to a v1.0 release because the spec is still not finished and it’s unclear how the library will be used. Nonetheless will v0.4 be a significant release with a mostly stable API and most functionality being implemented. Over the next five months we will fix the most pressing issues and make OpenMLS a usable MLS library for consumers to use. We are well aware that there is almost no experience with using MLS in a messaging product. (Cisco’s Webex is rolling out MLS for end-to-end encrypted video calls as part of their zero-trust initiative right now.) The goal is therefore to offer a mostly stable API and complete feature set for consumers to start using it. However, we expect a significant feedback cycle to improve the APIs to make OpenMLS better suited for applications. ...

In this blog post, I explore how MLS’ aspiration to be scalable manifests itself in OpenMLS. The charter in particular claims the following: Resource requirements have good scaling in the size of the group (preferably sub-linear) While performance can be theoretically analysed for MLS it is also interesting to see whether the performance goals hold up in a real implementation. This of course only looks at a single implementation. Nonetheless, I think that it gives a good impression on the actual performance of MLS implementations. Particularly because OpenMLS at this point is not optimised but rather implements the MLS spec as is. ...

We’re pleased to announce that we are engaging with INRIA Paris to cooperate on OpenMLS. ...