Re: consult on Tor(from a student)

[Paul Syverson <syverson@xxxxxxxxxxxxxxxx>]

On Mon, Mar 10, 2008 at 08:44:20AM +0800, chenxin chenxin wrote:
> 
> dear Paul :
>  I am a student instrested in anonymous communication systems. Nowadays, Tor is 
> the most popular anonymous network and the performance is good. Thanks you for 
> your providing so good technology. I have a question about Tor: I see the 
> framework of Tor to know Tor have some directory servers, Tor user should get 
> information from the DSs. I wonder that how the DSs prevent Dos attacks? Or 
> there are so large number of DSs that attackers cannot succeed Dos attack?
> I am sorry for my poor English.
> Looking forward for your letter.
> Thank you very much.
>                                             Yours Gates Chen

Hi Gates Chen,

Thanks for your interest. There are several Tor directory servers.  I
wouldn't claim they are immune to DoS but they are fairly resistant.
Besides there being an increasing number of them in diverse domains
and jurisdictions they tend to be on fairly high bandwidth
connections, etc.

The design of directory servers is now on its third main version, and
it continues to improve. Besides the servers there are many more
directory mirrors (perhaps enough to genuinely resist any DoS) so even
if all the directory servers were successfully attacked the network
would continue to function for a while---hopefully long enough to
recover from the DoS or to set up alternative servers.

HTH. I've cc'd or-talk which is the best place for such questions.
You caught me at a really rare moment when I had both attention
to see your query come in and time to respond. Usually from sheer
business I respond horribly late or never.

aloha,
Paul