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#include "head.wmi" TITLE="NLnet Project: Speed Up Tor Hidden Services"

<h2>NLnet Project: Speed Up Tor Hidden Services</h2>
<hr />

<p>
Tor Hidden Services allow users to set up anonymous information services,
like websites, that can only be accessed through the Tor network and are
protected against identification of the host that runs the services.
The most critical limitations of Tor Hidden Services are the time it takes
until a Hidden Service is registered in the network and the latency of
contact establishment when accessed by a user.
Due to design issues in the original Tor protocol,
the connection to a new Hidden Service can take several minutes, which
leads most users to give up before the connection has been established.
Using Tor Hidden Services for direct interactive user-to-user
communication (e.g. messaging) is nearly impossible due to the high latency
of Hidden Service circuit setup.
</p>

<p>
This project aims at speeding up Tor Hidden Services by improving the way
Tor circuits are set up between the user and the Hidden Service as well as
the way a Hidden Service is registered in the Tor network.
In a first step precise diagnostics of the behavior of the Hidden Services
in lab setups and real world situations will be conducted to find the
root causes of the bad timing effects.
Based on these diagnostics, optimization strategies will be designed and
verified for unwanted implications for the security and anonymity of the
Tor network.
The most promising optimizations will then be implemented to achieve a
notable improvement for the users. Precise success metrics will be
developed in the diagnostics phase, after it becomes clear where the time
is lost and what improvements are realistic.
The ultimate goal is to have the Hidden Services protocol change production
ready and propagated to the Tor users within a timeframe of less than
12 months.
</p>

<p>
This project is generously funded by:
</p>

<table width="100%" border="0" cellspacing="0" cellpadding="3">
<thead>
<tr>
<th><big>Project</big></th>
<th><big>Due Date</big></th>
</tr>
</thead>

<tr bgcolor="#e5e5e5">
  <td>
    <b>Deliverable A:</b> Analysis, measurements and problem
    clarification<br />
    <small><em>As Tor Hidden Services have not been actively developed
    further in the last year or so of Tor development, certain aspects of
    the problems are under-diagnosed. To identify the precise sources of
    latency and time loss, an extensive analysis of the deeper reasons for
    them needs to be conducted. Deliverable A will require about one month
    of work. The results of the analysis will influence the design
    decisions to be taken in Deliverable B.</em></small>
  </td>
  <td>
    June 15, 2008
  </td>
</tr>

<tr>
  <td>
    <b>Deliverable B:</b> Design and evaluation of the necessary
    changes<br />
    <small><em>The changes to Tor Hidden Services will affect core
    functionality of the protocol and therefore require a careful
    evaluation of possible repercussions for the security and anonymity. A
    two-month period is planned for the design and evaluation phase, which
    concludes with an extensive peer review.</em></small>
  </td>
  <td>
    August 15, 2008
  </td>
</tr>

<tr bgcolor="#e5e5e5">
  <td>
    <b>Deliverable C:</b> Implementation<br />
    <small><em>After design, evaluation and peer review the modifications
    need to be implemented and integrated with the current Tor code base.
    The actual implementation of the necessary changes will take
    approximately two months.</em></small>
  </td>
  <td>
    October 15, 2008
  </td>
</tr>

<tr>
  <td>
    <b>Deliverable D:</b> Implementation and test of the change up to
    release state<br />
    <small><em>The modification is highly critical to the security and
    anonymity of the Tor network, it requires extensive testing and
    debugging in laboratory and real life conditions. A period of three
    months is projected for testing and debugging, where the responsible
    developer is committed to the testing effort with 1/3 of its time. Part
    of the testing phase will be a public beta period.</em></small>
  </td>
  <td>
    January 15, 2009
  </td>
</tr>

<tr bgcolor="#e5e5e5">
  <td>
    <b>Deliverable E:</b> Rollout<br />
    <small><em>The actual rollout to the Tor server network will be
    conducted in sync with the regular Tor release schedule. As this
    schedule is dependent on a number of external factors, like the
    completion of other software projects that should go into the same
    release, the actual release time and the time until this release has
    been accepted and installed by most Tor server operators can vary. From
    experience a period of three to four months can be
    expected.</em></small>
  </td>
  <td>
    May 15, 2009
  </td>
</tr>
</table>

<br />

<a id="Reports"></a>
<h2><a class="anchor" href="#Reports">Monthly Status Reports</a></h2>
<p>
There will be in total eight monthly status reports beginning with the
first deliverable on June 15, 2008 and ending with completion of
implementation and testing work on January 15, 2009.
</p>

<table width="100%" border="0" cellspacing="0" cellpadding="3">
<thead>
<tr>
<th><big>Month,</big></th>
<th><big>Status Report</big></th>
</tr>
</thead>

<tr bgcolor="#e5e5e5">
  <td>
    <a id="Jun08"></a>
    <a class="anchor" href="#Jun08">Jun 08</a>
  </td>
  <td>
    <small><em>The original goal of analyzing the problems that lead to
    slowdown of Tor Hidden Services has been accomplished. Part of this
    analysis was measuring the delay that a user experiences when
    setting up or accessing a hidden service. Furthermore, measurement data
    from April 2008 could be leveraged to explore timings of internal
    substeps of establishing a connection to a hidden service. The results
    of this analysis are contained in a 22-page
    <a href="http://freehaven.net/~karsten/hidserv/perfanalysis-2008-06-15.pdf">report</a>
    that has been made public on the Tor
    <a href="http://archives.seul.org/or/dev/Jun-2008/msg00019.html">developer
    mailing list</a>.</em></small>
    <br/>
    <small><em>The analysis also unveiled a few bugs which were responsible
    for part of the delay in making a hidden service available for
    clients. Some bugs have been fixed subsequent to the analysis, others
    will be fixed soon. The evaluation has further brought up several
    possible approaches to improve Tor Hidden Service performance. Some of
    these ideas can be applied immediately, while others require deeper
    analysis and new measurements. Finally, in the course of the analysis,
    we discovered that some improvements require more in-depth
    changes to Tor which are not directly related to hidden services. These
    changes cannot be achieved in the time frame of this
    project.</em></small>
  </td>
</tr>

<tr>
  <td>
    <a id="Jul08"></a>
    <a class="anchor" href="#Jul08">Jul 08</a>
  </td>
  <td>
    <small><em>All bugs that have been found in the analysis have been
    fixed. This includes the 2 bugs that have already been fixed during the
    analysis and 4 more bugs that were fixed within the past 30 days. While
    the bugfixes remove unintended performance bottlenecks due to
    programming errors, some of the design changes that have been spotted
    in the previous analysis have side-effects on anonymity or overall
    network load which need to be evaluated against individual performance
    gains. A <a href="http://freehaven.net/~karsten/hidserv/discussion-2008-07-15.pdf">report</a>
    has been published to the
    <a href="http://archives.seul.org/or/dev/Jul-2008/msg00034.html">developer
    mailing list</a> including 7 possible design changes that need to be
    discussed. Some evaluations (namely Low-Bandwidth Measurements and the
    Grand Scaling Plan) have turned out to require more time than expected
    and had to be scheduled for a later time in the project than
    deliverable B. The current plan is to perform these evaluations within
    the timeframe until January 15 and work with assumptions until final
    results are available.</em></small>
  </td>
</tr>

<tr bgcolor="#e5e5e5">
  <td>
    <a id="Aug08"></a>
    <a class="anchor" href="#Aug08">Aug 08</a>
  </td>
  <td>
    <small><em>During the past 30 days the 7 proposed designs have been
    further evaluated and discussed. Four of them have proven to be
    applicable in terms of the required changes to the code and possible
    anonymity implications. One has been classified as bug rather than
    design change. Two had to be excluded for either unforeseeable security
    problems, or uncertainty of actual performance
    improvements.</em></small>
    <br/>
    <small><em>Together with the results from July 15, the design phase has
    been concluded. The tasks for the upcoming implementation phase are now
    quite clear: One bug needs to be fixed and four design changes need to
    be implemented. Further, evaluations of the changed design need to be
    performed in order to verify their usefulness. A
    <a href="http://freehaven.net/~karsten/hidserv/design-2008-08-15.pdf">report</a>
    with the results of the design phase has been published to the
    <a href="http://archives.seul.org/or/dev/Aug-2008/msg00025.html">developer
    mailing list</a>.</em></small>
  </td>
</tr>

<tr>
  <td>
    <a id="Sep08"></a>
    <a class="anchor" href="#Sep08">Sep 08</a>
  </td>
  <td>
    <small><em>During the first half of the implementation phase two bugs
    could be fixed that were related to hidden services: the
    <a href="http://bugs.noreply.org/flyspray/index.php?do=details&id=767">first
    bug</a> has already been identified in the design phase and was
    responsible for an unusual high failure rate when making a hidden
    service available in the system; the
    <a href="http://bugs.noreply.org/flyspray/index.php?id=814&do=details">second
    bug</a> was found during the implementation phase and was responsible
    for failure to connect to a working hidden service. Both bugfixes will
    be included in the next unstable version and likely be backported to
    one of the next stable releases.</em></small>
    <br/>
    <small><em>The four design changes that were proposed as result of the
    design phase have been implemented in an
    <a href="https://tor-svn.freehaven.net/svn/tor/branches/hidserv-design-changes/">experimental
    branch</a> of the unstable development tree. Early function tests have
    shown that these changes work and provide better (perceived)
    performance. This needs to be confirmed throughout the next four weeks
    in internal tests. The next goal is to prepare a release of this
    experimental branch that can be given out to beta testers at the
    beginning of the upcoming testing phase.</em></small>
  </td>
</tr>

<tr bgcolor="#e5e5e5">
  <td>
    <a id="Oct08"></a>
    <a class="anchor" href="#Oct08">Oct 08</a>
  </td>
  <td>
    <small><em>The implementation phase has been concluded. The bugfixes
    that were found in the past 30 days have been released in developer
    version <a href="http://archives.seul.org/or/talk/Oct-2008/msg00093.html">0.2.1.6-alpha</a>.
    The four design changes that were identified in the design phase have
    been specified in
    <a href="https://svn.torproject.org/svn/tor/trunk/doc/spec/proposals/155-four-hidden-service-improvements.txt">proposal 155</a>.
    Three design changes have been included in the development codebase and
    will automatically be included in the next development version. The
    first two design changes improve connection establishment to a hidden
    service by reducing a timeout from 60 to 30 seconds and by making a
    second attempt in parallel after a delay of 15 seconds. The third
    design change affects publication of a hidden service in the network by
    advertising the service at 5 rather than 3 points in the network in
    parallel and succeeding as soon as 3 points are established. The fourth
    design change has turned out to be rather ineffective, but would add
    considerable code complexity and was therefore dismissed. By now there
    are no more open bugfixes or new designs. All changes are in the
    development codebase and can be tested in the next phase.</em></small>
  </td>
</tr>

<br />

<a id="Links"></a>
<h2><a class="anchor" href="#Links">Links</a></h2>
<ul>
<li>Research paper on <b>Performance Measurements and Statistics of Tor
Hidden Services</b>
(<a href="http://www.uni-bamberg.de/fileadmin/uni/fakultaeten/wiai_lehrstuehle/praktische_informatik/Dateien/Publikationen/loesing2008performance.pdf">PDF</a>)
by Karsten Loesing, Werner Sandmann, Christian Wilms, and Guido Wirtz. In
the Proceedings of the 2008 International Symposium on Applications and the
Internet (SAINT), Turku, Finland, July 2008.

</ul>

</div>

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