OpenMLS 0.5 released

Today, we are releasing OpenMLS v0.5. This release has been a while in the making and covers substantial changes since the last release. We are grateful for the support of the Sovereign Tech Fund towards this goal. These are some of the changes:

  • The implementation caught up with the latest changes in the protocol specification. The last version was roughly based on draft 12. Since then, the protocol has iteratively evolved all the way through draft 20. The library now implements the wire format of messages and mechanisms specified in RFC 9420.
  • Extensive interoperability testing has been done between OpenMLS, Cisco‚Äôs MLS++, and another closed-source MLS protocol implementation. The goal of this exercise was to validate the last set of changes in the specification and ascertain that all implementations implemented the specification correctly.

The next phase

Until recently, the specification was a moving target and so was the implementation. Now that the specification is no longer subject to changes, the implementation can finally mature in terms of correctness, ease-of-use, and efficiency. We would like OpenMLS to be as useful as possible to those who consider end-to-end encryption with MLS. We are ready to evolve the library in the following areas:

  • Stabilize the persistence format
  • Improve and harmonize the API
  • Improve efficiency
  • Support new platforms
  • Add optional features and extensions

Looking for help?

If you are looking to use OpenMLS in your project the OpenMLS team can offer professional help with consulting or with implementing. We can accelerate the development of the items listed above or offer a more bespoke solution. Drop us an email at