Check out www.megaepic.com/~johnston/newencryption.txt - its a proposal
that we're working on to get some better encryption support into jabber.
This looks good. I'm glad to see it piggybacking on a standard XML encryption scheme, especially one that can contain an entire <message> element.
For public key exchange, why not store the key (a complete certificate, actually) on the server using the public data space* described in [JPO 1.6.10] (confusingly under the "jabber:iq:private" namespace description!) Just declare a new namespace like "jabber:public:publickey" and store your certificate in an XML element. No new protocol needed.
The only issue I can see is that it allows anyone to get the public key, but that shouldn't cause problems; it is after all a public key. If only buddies could get it, you wouldn't be able to send a signed message to a non-buddy and have them be able to verify it.
You note that key exchange is vulnerable to attack. I think this isn't an issue if what's exchanged is a full certificate signed by a reputable CA, since no one could spoof such a certificate. Right?
�Jens
(*In general I'm pretty excited about this public data space, which I just discovered last night since its description is pretty well concealed :-) In particular I think can be the solution to my earlier issue about how to transfer buddy icons -- just store a small image under a particular namespace, and anyone who wants to display your picture in their buddy list can download it. There are a couple of issues which I'll address in a proposal I plan to post ASAP.)
