Re: no circuit loops?

[Roger Dingledine <arma@mit.edu>]

On Fri, Oct 24, 2003 at 10:55:25AM +0100, Andrei Serjantov wrote:
> > It's tricky because we have constraints, such as who can be our exit
> > node, that mean we need to think ahead a little bit, so we don't e.g.
> 
> Surely, you choose from the "other end", right? Assuming the topology is
> not restricted, choose the exit node, then choose all the others uniformly
> without replacement.

I also want to let users configure a choice for their first hop. If you
live inside a company that runs a Tor node on its firewall, it's dumb
to choose moria as your first hop rather than your local Tor node.

> Yes, but you need to be able to choose paths sensibly if the user alters
> the default and the "shortcutting loops" problem is a real one. i.e. you
> do not want under any circumstances your first and last router to be the
> same.

Yes, this is an additional constraint. So that gives us:
* the first hop is either fixed or totally free
* the last hop must be something with an ok exit policy
* the first hop and the last hop must be different
* no two adjacent routers should share the same onionskin key

Did I miss any?

--Roger