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Re: [tor-bugs] #6232 [Analysis]: Make entropy-over-time graph
#6232: Make entropy-over-time graph
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Reporter: arma | Owner:
Type: enhancement | Status: needs_review
Priority: normal | Milestone:
Component: Analysis | Version:
Keywords: | Parent:
Points: | Actualpoints:
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Comment(by asn):
Replying to [comment:30 robgjansen]:
> Replying to [comment:29 asn]:
> > Replying to [comment:28 robgjansen]:
> > > We are still missing the graph where each of the plots are
represented as a percentage, computed as: (entropy / max_entropy). See my
first post above.
> >
> > Say, if the entropy of the current consensus is 8 bits, and the
maximum possible entropy is 11 bits, do you think that 70% would be the
correct figure in this case? It seems like that the logarithmic scale
gives us an overrated percentage.
> >
> > Maybe we should transform the values to the linear scale (`2^8/2^11`)
to get a more intuitive percentage. Or is there a better way to represent
this comparison?
>
> I don't understand your opposition, but it shows that the meaning of
entropy to describe anonymity is not well understood. (I've been asking
'WTF does entropy mean?' all along.)
>
> Read [http://www.freehaven.net/anonbib/cache/Diaz02.ps.gz this paper],
particularly Section 3.
Oh, I did not oppose your idea; I also agree that entropy and bits are not
intuitive ways of measuring diversity or whatever we are trying to measure
here.
What I tried to say is that '''maybe''' ''degree of anonymity'' is not the
most intuitive way of graphing ''How far away are we from the ideal
network (wrt bandwidth weights) of 'n' nodes''. I'm saying this because
entropy is measured in logarithmic units and the logarithmic scale is
harder to understand than the linear scale (IMO).
For example, what does a `0.76` ''degree of anonymity'' means? It does
'''not''' mean that the ''current Tor network'' is 76% of a ''perfect Tor
network'' because of the logarithmic nature of entropy. That's the reason
I asked if it would be more helpful to conver the <entropy>/<max entropy>
figure to the linear scale.
In any case, ''degree of anonymity'' should be more intuitive than plain
entropy: I coded the change in branch `bug6232` of `git://gitorious.org
/metrics-tasks/metrics-tasks.git` (https://gitorious.org/metrics-tasks
/metrics-tasks/commit/e54b4278361184bf6ff90f189898668160474f2f).
Also, thanks for the link to the paper.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6232#comment:31>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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