no circuit loops?

Andrei Serjantov aas23 at
Fri Oct 24 09:46:34 UTC 2003

> On the one hand, a loop has an obvious threat from any "repeat node" since
> it can trivially recognize circuits with that loop and thus bypass it
> (long range padding and leaky pipes could reduce this slightly, but
> still...).
> On the other hand, the absence of loops gives information about a
> circuit. E.g., there is an observer on OR_1's network connections.
> Alice connects through OR_1, OR_2, OR_3, OR_4, OR_5.  OR_4 is bad.
> The adversary can now rule out OR_2 and OR_3 as exit points
> even though their net connections are not visible to it.

This is an interesting argument for having substantial numbers of Onion
Routers (but not *too many* as I argue elsewhere).  I suspect if you have
many more routers than your route length, the problem becomes


Andrei Serjantov
Queens' College
Cambridge CB3 9ET

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