Re: [tor-talk] Another Hidden Service question

[Roger Dingledine <arma@xxxxxxx>]

On Tue, Feb 12, 2013 at 09:11:33AM +0000, Nathan Freitas wrote:
> Does the fact that my actual IP address has changed (say my Tor client
> moves from a 3G to a wifi connection), or by extension, by Tor client
> has stopped and started, have any impact on the availability of a Hidden
> Service I am hosting?

Yes -- your hidden service holds open circuits to its intro points,
and if it loses those circuits, it won't be able to hear about clients
who want to reach it.

I believe the current behavior is that when it loses those circuits,
it chooses new intro points and makes new circuits to them -- which
means anybody who has the old hidden service descriptor is going to be
introducing herself to the wrong intro points.

> What I am seeing is that I can initially connect to a HS hosted on my
> Android phone from a remote computer when the phone is on wifi. However,
> when I switch to 3G, I am unable to connect from the same remote
> computer anymore, and the same issue when I return to wifi.

Sounds like the new feature you want is "if our intro circuits close, but
it was because our network failed and not because the intro points failed,
reestablish new intro circuits to the *old* intro points." The main tricky
point there is distinguishing "network failed" from "intro points failed".

If you want them to survive restarts of the Tor client, that's more
complex -- either Tor needs to cache its recent intro point choices to its
state file, or it needs to look up its own hidden service descriptor and
if it's recent enough, re-use those intro points. Both are kind of ugly.

> I understand that HS were designed for "servers", but this research I am
> doing is using them more in a client mode, similar to TorChat, though in
> a manner I hope doesn't trash the Tor network or otherwise cause
> scalability issues.

--Roger

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