XMPP: Allowing clients to communicate through a proxy?

Question

So I'm working on this site web app that should let users easily chat with untrusted other members if they want to with their own software like Goog Chat, Facebook, etc (not the central feature though).

So to combine "easily" and "their own client" with "untrusted," I envision a feature like so:
1. Bob wants to chat with Alice. Both have XMPP clients.
2. Bob clicks on Alice.
3. My site sets up an XMPP "relay"/"proxy" through which Bob and Alice can gets each others' messages, but their XMPP identities are never revealed to the other -- only my sites "proxy" XMPP indentity.

Bob <-> ProxyThatHidesIdentities <-> Alice

Is there a good mechanism for doing this?

Answer 1

This sounds like regular XMPP Multi User Chat (MUC), but in this particular case you're just restricting rooms to a maximum two participants.

With MUC, chat rooms can be fully anonymous; people just choose (or you enforce) aliases and so the XMPP addresses appear to each user as [email protected]/bob, where example.com is your server. Neither party's origin XMPP ID appears to others.

However, this would require each party to have a client that supports MUC. Most do, but whether the native Google Talk client does, I have no idea.

I'd also note that Facebook users currently cannot talk to anyone outside the Facebook network via XMPP (or any other means).