Re: [tor-talk] Finding relay Sybils / Groups [re: relay_early/blackhat]

[Aymeric Vitte <vitteaymeric@xxxxxxxxx>]

Le 30/07/2014 20:10, grarpamp a écrit :
> There may be more questionable relays to be found.

Probably not.

We see in the description of this attack some subtle details, along with 
a list of papers/studies.

The problem is that the Tor network is really too small in terms of 
efficient nodes, so if you add the proper amount of efficient nodes a 
correlation attack seems easy without any subtility.

Taking Guards and Exit nodes, asking Onionoo you get something like 1000 
for each (version > 2.3.0).

Testing them you were used to get 500 for each (ie really working at 
instant t).

Filtering on bandwitdth > 2 MBps for Guards, you were used to get 250  
(only).

Among the remaining number of exit nodes it's not rare that some have 
some specific exit policies, ie exiting nothing, so a not negligible 
number to be banned.

Trying this right now gives (unexpectedly) only 121 Guards (> 2MBps) and 
130 Exit nodes, really working.

Behind these numbers, the issue is still how to add efficient nodes not 
controlled by the same people, maybe it could be envisioned to evolve to 
a more decentralized system where small nodes can be efficient.

Regards,

--
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