[tor-dev] automatically detect many new identical/similar bridges

teor teor2345 at gmail.com
Wed Dec 14 21:53:31 UTC 2016

> On 15 Dec. 2016, at 06:01, nusenu <nusenu at openmailbox.org> wrote:
>> How could we avoid an adversary brute-forcing all the possible ASs and
>> days/hours?
> I'm not sure I understand what you mean by brute-forcing in this case
> since I would not suggest any deterministic algorithm (like a hash) that
> takes an ASname and a timestamp and produces a string but just a
> AS number -> random id
> mapping, stored for a day or an hour and deleted after that.
> Another way an attacker could take advantage of this:
> unique AS sign-up rate patterns
> "everyday there are about x new bridges in AS y" so it doesn't help much
> if we change the random AS id daily.

If an adversary submits a bridge descriptor from every (popular) AS
(in every hour of) every day, they know which AS each bridge is from.

Or, alternately, if they submit a bridge descriptor from an AS they
are watching, then they know all the bridges in that AS.

And they don't actually need to be in the AS to submit a descriptor
with an IP address from that AS.


Tim Wilson-Brown (teor)

teor2345 at gmail dot com
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