en/hidden-services.wml (529ea82f7) - tor-webwml.git

hidden-services.wml

## translation metadata
# Revision: $Revision: 14229 $
# Translation-Priority: 3-low

#include "head.wmi" TITLE="Tor: Hidden Service Protocol"

<h2>Tor: Hidden Service Protocol</h2>
<hr />

# TO TRANSLATORS: this page might still need some review and corrections!
# better wait at least one week from today (2008-03-29) before starting
# translation

<p>
A hidden service needs to advertise its existence in the Tor network before
clients will be able to contact it. Therefore, the service randomly picks
some relays, builds circuits to them, and asks them to act as introduction
points telling them its public key. Note that in the following figures the
green links are circuits rather than direct connections. This makes it
impossible for anyone to associate the introduction points with the hidden
service's IP address. This is important, because although the introduction
points and others are told the hidden service's identity (public key), they
must not learn about the hidden server's identity (IP address).
</p>

<img alt="Tor hidden service step one" src="$(IMGROOT)/THS-1.png" />
# maybe add a speech bubble containing "PK" to Bob, because that's what
# Bob tells to his introduction points

<p>
In a second step, the hidden service assembles a hidden service descriptor
containing the introduction points' addresses and its public key and signs
it with its private key. It stores that descriptor on a set of directory
servers, again using a circuit that hides the link between storing the
descriptor with the hidden service's IP address. The descriptor will be
found by clients requesting XYZ.onion where XYZ is uniquely derived from
the service's public key. After this step, the hidden service is set up.
</p>

<img alt="Tor hidden service step two" src="$(IMGROOT)/THS-2.png" />
# maybe replace "database" with "directory servers"; further: how incorrect
# is it to *not* add DB to the Tor cloud, now that begin dir cells are in
# use?

<p>
A client that wants to contact a hidden service needs to learn about its
onion address first. After that, the client can initiate connection
establishment by downloading the descriptor from the directory servers. If
there is a descriptor for XYZ.onion (the hidden service could also be
offline or have left long ago, or there could be a typo in the onion
address), the client creates a circuit to another randomly picked relay and
asks it to act as rendezvous point, telling it a one-time secret.
</p>

<img alt="Tor hidden service step three" src="$(IMGROOT)/THS-3.png" />
# maybe add "cookie" to speech bubble, separated from the surrounded
# "IP1-3" and "PK"

<p>
Upon setting up the rendezvous point, the client assembles an introduce
message (encrypted to the hidden service's public key) including the
address of the rendezvous point and the one-time secret. The client sends
this message to one of the introduction points, requesting it to deliver it
to the hidden service. Again, communication takes place via a circuit, so
that nobody can relate sending the introduce message to the client's IP
address, ensuring the client's anonymity.
</p>

<p>
The hidden service decrypts the client's introduce message and finds the
address of the rendezvous point and the one-time secret in it. The service
creates a circuit to the rendezvous point and sends the one-time secret to
it in a rendezvous message.
</p>

<img alt="Tor hidden service step five" src="$(IMGROOT)/THS-5.png" />
# it should say "Bob connects to Alice's ..."

<p>
In the last step, the rendezvous point notifies the client about successful
connection establishment. After that, both, client and hidden service can
use their circuits to the rendezvous point for communicating with each
other. The rendezvous point simply relays (end-to-end encrypted) messages
from client to service and vice versa.
</p>

</div>

#include <foot.wmi>

tor-webwml.git

Move hidden service protocol explanations to own page.