[tor-talk] Reasoning behind 10 minute circuit switch?

Paul Syverson paul.syverson at nrl.navy.mil
Tue Oct 14 18:37:25 UTC 2014

On Tue, Oct 14, 2014 at 01:05:57PM -0400, Nick Mathewson wrote:
> On Tue, Oct 14, 2014 at 12:17 PM, Greg Norcie <gnorcie at umail.iu.edu> wrote:
> > Hi all,
> >
> > I'm working on doing a study on user tolerance of delays (for example,
> > latency on Tor).
> >
> > During our discussion, a bit of a debate occured about the TBB's circuit
> > switching. I was wondering if there's any research that's been done to
> > arrive at the 10 minute window for circuit switching, or if that was number
> > picked arbitrarily?
> If I'm reading the source right:  Back before commit
> d2400a5afd70b009b632b307205273fc25c8cd92 from 2005, the number was 30
> seconds.  But that was too short and led to unacceptable performance.
> So Roger picked 10 minutes more or less intuitively.

If I recall, we (Roger, Nick, and I) had a bunch of discussions
concerning the trade-offs between the overhead of the public-key
operations of circuit building and the pseudonymous profiling
occurring at an exit. (The intersection threats from repeated circuit
builds was not uppermost in our thoughts at that point. We were aware
of the potential. But this was before we did the research that so
strongly motivated the need for guard nodes.) The ten minute choice
was an informed one, and we had some numbers on public-key overhead.
But we had no hard usage data or similar on which to base our


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