Tom Ritter <t...@ritter.vg> writes:
> On Thu, 16 May 2019 at 11:20, George Kadianakis <desnac...@riseup.net> wrote:
>> 3) Duration of Activity ("DoA")
>>
>> The USENIX paper uses the period of time during which circuits send and
>> receive cells to distinguish circuit types. For example, client-side
>> introduction circuits are really short lived, wheras service-side
>> introduction circuits are very long lived. OTOH, rendezvous circuits
>> have
>> the same median lifetime as general Tor circuits which is 10 minutes.
>>
>> We use WTF-PAD to destroy this feature of client-side introduction
>> circuits by setting a special WTF-PAD option, which keeps the circuits
>> open for 10 minutes completely mimicking the DoA of general Tor
>> circuits.
>
> 10 minutes exactly; or a median of 10 minutes? Wouldn't 10 minutes
> exactly be a near-perfect distinguisher? And if it's a median of 10
> minutes, do we know if it follows a normal distribution/what is the
> shape of the distribution to mimic?
>
Oops, you are right, Tom.
It's not 10 minutes exactly. The right thing to say is that it's a median
of 10 minutes, altho I'm not entirely sure of the exact distribution.
These circuits basically now follow the MaxCircuitDirtiness
configuration like general circuits, and it gets orchestrated by
circuit_expire_old_circuits_clientside(). Not sure if it's in a spec
somewhere.
I will update the spec soon with the fix. Thanks!
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