[tor-dev] Finding the HSDIR responsible for a certain onion address

[Donncha O' Cearbhaill]

A Tor client generates the desc_id for the v2 hidden service it would like
to query. It did selects the 3 HSDIR from the router list which are found
directly after the position of the desc_id when the routers are sorted by
their identity digest (hash of their onion public key). I took me quite a
while to figure out exactly how this works from the relatively sparse info
in the rend-spec.txt.

I just put up a Gist with the python implementation of desc_id calculation.
It should be pretty straightforward using STEM to sort list of OR's with
the HsDir flag by identity_digest and determine which 6 are responsible at
the current time.

https://gist.github.com/DonnchaC/5451637



On Wed, Apr 24, 2013 at 11:23 AM, Frank Young <pfcodes at gmail.com> wrote:

> Dealing with v2 hidden service descriptors, how does a tor client get
> the list of HSDIR are responsible for a certain onion address so it
> can contact them for descriptor of the hidden service?.
>
> According to rend-spec.txt the list of the responsible HSDIR for a
> particular hidden service changes almost in every 24.
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