[tor-dev] Time interval for changing Introduction Points in Tor Hidden Services

[David Goulet]

On 16 Mar (00:16:19), Piyush Kumar Sharma wrote:
> Hi all,
> 
> I have been investigating the Tor hidden services for some research work.
> 
> I am finding it hard to obtain information about how often do Introduction
> Points of hidden service change.
> 
> More specifically, I am looking for answers to the following questions:
> 
> 1.) If the tor relays selected as Introduction Points for a hidden service
> go down (e.g., due to DoS), then in what time duration does the hidden
> service select new Introduction Points automatically?

Almost immediately. Basically, if the introduction circuit collapses, the
service will select a new one, update its descriptor and upload them.

> 
> 2.) Even when the Introduction Points are not down, is there a duration
> after which they are automatically changed by the hidden service? If so,
> what is this duration?

Yes, it is a random value between 18h and 24h.

https://gitlab.torproject.org/tpo/core/tor/-/blob/main/src/feature/hs/hs_service.c#L481

> 
> I have already tried to find this information in the Tor-spec about onion
> v3 services. But could not find answers to these specific questions.

Yeah, these are mostly implementation details rather than specific to the
protocol.

And so unfortunately, these details can only be found in the source code.

David

-- 
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