I would like to know if there is any group chat solution that can be used today with reasonable confidence that the content of the conversations will remain private. So far, these are the solutions I'm aware of:
IRC with SSL, plus FiSH: I'd rather avoid this, not only because it involves setting up an IRC server, but also because it employs Blowfish, which isn't recommended anymore even by it's creator.
Private XMPP server, with SSL: It's relatively easy to set up an XMPP server, which allows one to keep control over his data. The downside is that the messages themselves are not encrypted: I've seen some discussions and some papers about an mpOTR protocol, but no implementation. (this is what I'm currently using)
Tox: As far as I understand, being a peer-to-peer protocol the risk of leaking information should be minimal, plus it employs modern cryptographic primitives (curve25519, xsalsa20, and poly1305, from the NaCl crypto library). On the other hand, it is still in its infancy, and I wonder if there have been any audits or studies on the actual security it provides. Can Tox be considered reasonably safe or is it too early to tell?
Finally, did I miss some other interesting solution?
Update: Several other solutions have been proposed in the answers below, and some of them look promising. On the other hand, two of those are actually outside the scope of this question, and I would like to point out why because they are the most referenced I found on the internet, including this site.
Any protocol (usually XMPP), plus OTR: For one-on-one conversations OTR is great, and the de-facto standard. On the other hand, it doesn't support group chats, which are the focus of this question. The only multi-party OTR implementation I am aware of is Cryptocat's but... see below. (this covers Jitsi, ChatSecure, and many other clients)
Cryptocat: It was a great solution, but the project has been inactive (and unavailable) since February 2014. Its creator mentioned a big rewrite and upgrade in the works, but it is unclear when or if this will be available. See the notice on the project's homepage.