Block directory authorities, is it possible?

[Pei Hanru <peihanru@xxxxxxxxx>]

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Hi all,

I live in China and was/am having difficulties in using Tor, the problem
is: it takes quite a long time to build a circuit for the first time I
start Tor on my Windows machine.

I think it is because of the earthquake that destroys the fibers at the
seabed near Taiwan at the end of 2006, communications to the US were
almost blocked, to the EU were jammed. So it is very difficult to
download a new network-status from a directory authority.

Excerpt from dir-spec.txt:

	Clients discard all network-status documents over 24 hours old.
	[...]
	When a client has no live network-status documents, it downloads
network-status documents from a randomly chosen authority.

Well, Tor will finally recover here when the fibers are repaired. But
this reminds me of a possible attack against the Tor network, say, if
the notorious Great Firewall of China blocks *all* the connections to
*all* the directory authorities (currently 5 I believe), then Tor will
will become completely useless in China. Considering the number of
directory authorities, this doesn't seem to be infeasible. (In fact, I
think this is easy to some extent.)

Am I understanding correctly? Are there any actions Tor can take? After
all, we cannot simply assume this will not happen in the future.

Regards,
Hanru
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