[OTR-dev] Multiple Accounts online

[Greg Troxel]

Ian Goldberg <ian at cypherpunks.ca> writes:

> On Sun, Jun 05, 2005 at 09:58:30PM -0400, alex323 wrote:
> > Heh. I recently discovered that OTR doesn't like it when I am logged in 
> > once from two different machines. I've read the protocol enough to know 
> > why :)
> > 
> > Any ideas to support this?
> 
> That's a known problem with protocols (like AIM, since they changed its
> behaviour) that allow you to log in more than once, and send copies of
> your incoming messages to all of your logins.  [Jabber, for example,
> doesn't have this problem, since it distinguishes your logins.]

Jabber doesn't have this problem, but I find otr/jabber to be
problematic.  I think the problem arises from sending messages without
an explicit resource until there is a conversation in progress, but I
haven't tracked it down.

> What *should* happen here?  If Alice is logged in multiple times, and
> Bob tries to start an OTR conversation with her, all of her clients
> will receive the OTR Query message, and will respond with a Key
> Exchange.  Bob will then receive multiple Key Exchanges.  What should he
> do then?  [It's even worse if Bob is also logged in multiple times!]

This is a tough call, but it seems that e2e crypto state requires
naming (weakly) the actual endpoints, so someone we have to construct
point-to-point channels from the multicast channel that is provided.
So one would have to add resource names on top of things like AIM.

-- 
        Greg Troxel <gdt at ir.bbn.com>