[metrics-team] PrivCount in Tor session in Rome

teor teor2345 at gmail.com
Tue Mar 13 11:06:45 UTC 2018

> On 13 Mar 2018, at 11:41, Karsten Loesing <karsten at torproject.org> wrote:
> Hi teor,
>> On 2018-03-13 09:00, teor wrote:
>>>> 2. What analysis can the metrics team do to help with PrivCount
>>>> design/development? There's something in the notes about flags changing
>>>> in 24 hour periods or possible partition of relays. Can you elaborate
>>>> and make these questions a lot more concrete? Maybe this is something I
>>>> can do in the next few days, with enough time for you to discuss more
>>>> with irl while you're in Rome?
>>> We want to partition the reporting relays into 3 groups at random.
>>> (Or maybe some other number: there is a tradeoff between the number of
>>> groups, which resists manipulation by a single relay, and the quality of the
>>> resulting statistic.)
>>> If we select relays from the consensus at random, do we get a roughly
>>> even distribution of consensus weight, guard weight, middle weight, and
>>> exit weight?
>>> What if we only have 5% of relays reporting statistics?
>>> Can we still get roughly even total partition weights at random?
>>> (Please choose relays on the latest tor versions, because they will be the
>>> first to deploy PrivCount.)
> Here's a graph (with and without annotations):
> https://people.torproject.org/~karsten/volatile/partitions-2018-03-13.pdf
> https://people.torproject.org/~karsten/volatile/partitions-2018-03-13-annotated.pdf

0.3.2 has the expected consensus weight distribution.
And it's 2 months since 0.3.2 became stable:

I would be happy to wait 2 months after a stable release for good statistics.

> Let me know if this makes sense, or which parameters I should tweak.

Can we focus on 0.3.2, and all relays?

> For
> example:
> - Different number of groups (currently 3).

Can we try 3 and 5?

> - Different number of simulations (currently 1000).

That's fine.

> - Different number of consensuses as input (currently 1).

We'll be collecting over a day, so please use 24 consensuses.

>>> If we can't get even partitions by choosing relays at random, we will need
>>> to choose partitions weighted by consensus weight. Let's decide if we
>>> want to do that analysis after we see the initial results.
> Let me know if you want me to try out a different algorithm. The current
> algorithm simply assigns relays to groups at random.

That seems to get us what we want, let's keep selecting at random.

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