[tor-relays] Publishing bridge contact information

Karsten Loesing karsten at torproject.org
Thu Feb 8 08:42:49 UTC 2018

On 2018-02-07 19:37, Sebastian Hahn wrote:
>> On 7. Feb 2018, at 18:55, Geoff Down <geoffdown at fastmail.net> wrote:
>> On Wed, Feb 7, 2018, at 4:45 PM, Karsten Loesing wrote:
>>> Possible disadvantages are:
>>> - If somebody runs a relay and a bridge, both with the same contact
>>> information, a censoring adversary might guess that the bridge might run
>>> on a nearby IP address as the relay. However, they could as well assume
>>> that for all relays and block or scan the IP space around all known relays.
>>> - Bridge operators might be surprised to see their contact information
>>> in a public archive. We do have a warning in the tor manual
>>> https://www.torproject.org/docs/tor-manual.html.en#ContactInfo, but
>>> maybe nobody reads the fine manual.
>> An email address may be linked to an IP address in public sources, e.g. mailing list archives, forum postings.
> ... or whois information.


These sound like variants of the first disadvantage listed above. There
are two additional assumptions in here, though:

 1) bridge operators use the same or a similar email address as their
bridge contact information and for mailing list/forum postings or in
their whois information;

 2) bridge operators are running their bridges close to the host they're
using to post to mailing lists/forums or close to the host where they're
hosting a registered domain.

I can see situations where both assumptions are met. But I think,
overall, that the likelihood of locating a bridge by connecting contact
information to mailing list archives, forum postings, or whois
information makes this attack rather unattractive.

I'd say let's list this as another possible disadvantage, and let's
compare them all to the possible advantages at the end.

Unless you thought of this as a show-stopper, in which case I'd kindly
ask you to elaborate.

Thanks for the feedback, Geoff and Sebastian!

All the best,

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