Re: Bridge status website

[Sebastian Hahn <hahn.seb@xxxxxx>]

On May 26, 2010, at 1:33 PM, Christian Fromme wrote:
> I wonder whether (b) is a good idea. Say I am Sir John McEvil and I
> want to learn something about which IP address belongs to which
> bridge: All I gotta do is iterate connections from some obscure
> countries to certain bridges and check the stats later on.

This isn't really an issue: If they adversary has the ability to push
traffic through a bridge, it can learn its descriptor, and thus its
fingerprint. The hashed fingerprint is used to look up the bridge on
the website.

This attack would be more interesting if knowing the bridge
descriptor didn't give you the ability to make the query.

> I'd like to add something else instead: Giving out information about
> which bridge is known to be blocked in which country maybe? I know
> that feature isn't in BridgeDB yet, but it is on my TODO-list for it.
> I don't see much risk in disclosing this information, but it'd bring
> some sort of awareness and also offers data for researchers.

I think this is probably hard to do reliably, as blockings are very
inhomogenous if you look at an entire country. Another point
is that seeing no Burmese users on my bridge doesn't mean the
bridge is blocked there - maybe nobody has gotten its descriptor,
or the people who have it turned off their Tor. This will be more
common as we gain more bridges.

Deciding when a country has blocked a bridge is something
that will need more research, imo. Once we've come up with
a good metric or possibly even some active testing, we could
integrate that later. I generally wonder what bridge operators
want to do with that information, though. There isn't really much
they can do other than change their ip - but if the bridge is still
working for some people, changing its IP also means sadness.

> Thanks,
> /C

Sebastian