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

[teor <teor2345@xxxxxxxxx>]

> On 14 Dec. 2016, at 21:09, nusenu <nusenu@xxxxxxxxxxxxxxx> wrote:
> 
> another raw idea:
> 
> - would the bridge auth be willing to publish a randomly generated AS
> identifier (regenerated daily) that allows new bridges added on the same
> day to be grouped by that identifier without directly disclosing the AS
> itself.

Bridges don't necessarily contact the bridge auth before producing their
descriptors. So we'd need a protocol change to do this.

> Note: This introduces a confirmation opportunity, where attackers can
> learn the AS in which a new bridge is added if they added a bridge in
> the same AS on the same day. To reduce this problem it could be a hourly
> generated identifier.

How could we avoid an adversary brute-forcing all the possible ASs and
days/hours?

We can use the shared random value in the consensus to prevent relays
knowing their position on the hidden service hash ring in advance, but
there's nothing stopping someone brute-forcing it in arrears.

So we'd need a concrete protocol that would allow correlation, but not
be able to be brute-forced. And we'd need something that doesn't have
a single point of failure (if only we had two bridge authorities, they
could do the shared random protocol).

Hmm, still worth thinking about...

T

-- 
Tim Wilson-Brown (teor)

teor2345 at gmail dot com
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