Works great. Definitely check it out. (I found Matrix after trying to write an XMPP client and becoming a giggly/teary-eyed wreck trying to parse out how many incomplete extensions I would have to implement to get multi-device working. Previously: [1]) I now use matrix daily from all of my devices, mobile and desktop alike.
They're also working on an Axolotl rachet implementation: https://matrix.org/git/olm/ It's not integrated yet, sadly, but I'm eagerly awaiting seeing it jump in as a first-class supported feature.
I'm conflicted on Axolotl. For every layer of security you add, you increase the odds of someone doing something careless (this[1] is way more common than you'd think).
Key-leak healing is an interesting function out-of-the-box, but if your priv key gets uploaded accidentally, odds are so did your DH Identity/Ratchet/Chain keys as well, effectively rendering you "fully compromised". It only offers protection in an instance where you keep your keys compartmentalized.
Is there a general consensus within the crypto community as to whether a) this is conceptually sound, and b) if there's an audited implementation? It's so so easy to mess up and have that error be overlooked (i.e. the OpenSSL debacle), which makes me want to just stick with the tried and true GPG DH/ELG setup with PKI and revocation. Definitely a real interesting project to watch and a real interesting take on perfect-forward secrecy though! Thanks for your feedback. If you see this, read my other post in this thread and e-mail me, I'd love your feedback.
They're also working on an Axolotl rachet implementation: https://matrix.org/git/olm/ It's not integrated yet, sadly, but I'm eagerly awaiting seeing it jump in as a first-class supported feature.
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[1]: https://news.ycombinator.com/item?id=9772968