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## translation metadata # Revision: $Revision$ # Translation-Priority: 4-optional #include "head.wmi" TITLE="Tor: Volunteer" CHARSET="UTF-8" <div id="content" class="clearfix"> <div id="breadcrumbs"> <a href="<page index>">Home » </a> <a href="<page getinvolved/volunteer>">Volunteer</a> </div> <div id="maincol"> <!-- PUT CONTENT AFTER THIS TAG --> <h1>A few things everyone can do now:</h1> <ol> <li>Please consider <a href="<page docs/tor-doc-relay>">running a relay</a> to help the Tor network grow.</li> <li>Tell your friends! Get them to run relays. Get them to run hidden services. Get them to tell their friends.</li> <li>If you like Tor's goals, please <a href="<page donate/donate>">take a moment to donate to support further Tor development</a>. We're also looking for more sponsors — if you know any companies, NGOs, agencies, or other organizations that want anonymity / privacy / communications security, let them know about us.</li> <li>We're looking for more <a href="<page about/torusers>">good examples of Tor users and Tor use cases</a>. If you use Tor for a scenario or purpose not yet described on that page, and you're comfortable sharing it with us, we'd love to hear from you.</li> </ol> <a id="Documentation"></a> <h2><a class="anchor" href="#Documentation">Documentation</a></h2> <ol> <li>Help translate the web page and documentation into other languages. See the <a href="<page getinvolved/translation>">translation guidelines</a> if you want to help out. We especially need Arabic or Farsi translations, for the many Tor users in censored areas.</li> <li>Evaluate and document <a href="<wiki>doc/TorifyHOWTO">our list of programs</a> that can be configured to use Tor.</li> <li>We have a huge list of <a href="<wiki>doc/SupportPrograms">potentially useful programs that interface to Tor</a>. Which ones are useful in which situations? Please help us test them out and document your results.</li> </ol> <a id="Advocacy"></a> <h2><a class="anchor" href="#Advocacy">Advocacy</a></h2> <ol> <li>Create a presentation that can be used for various user group meetings around the world.</li> <li>Create a video about the positive uses of Tor, what Tor is, or how to use it. Some have already started on <a href="https://media.torproject.org/video/">Tor's Media server</a>, <a href="http://www.howcast.com/videos/90601-How-To-Circumvent-an-Internet-Proxy">Howcast</a>, and <a href="http://www.youtube.com/thetorproject">YouTube</a>.</li> <li>Create a poster, or a set of posters, around a theme, such as "Tor for Freedom!".</li> <li>Create a t-shirt design that incorporates "Congratulations! You are using Tor!" in any language.</li> </ol> <a id="Projects"></a> <h2><a class="anchor" href="#Projects">Projects</a></h2> <p> Below are a list of Tor related projects we're developing and/or maintaining. Most discussions happen on IRC so if you're interested in any of these (or you have a project idea of your own), then please <a href="<page about/contact>#irc">join us in #tor-dev</a>. Don't be shy to ask questions, and don't hesitate to ask even if the main contributors aren't active at that moment. </p> <table id="projects"> <tr> <th>Name</th> <th>Category</th> <th>Language</th> <th>Activity</th> <th>Contributors</th> </tr> <tr> <td><a href="#project-tor">Tor</a></td> <td>Core</td> <td>C</td> <td>Heavy</td> <td>nickm, arma, Sebastian</td> </tr> <tr class="alt"> <td>*<a href="#project-jtor">JTor</a></td> <td>Core</td> <td>Java</td> <td>None</td> <td></td> </tr> <tr> <td><a href="#project-tbb">TBB</a></td> <td>Usability</td> <td>Sys Admin</td> <td>Moderate</td> <td>Erinn</td> </tr> <tr class="alt"> <td><a href="#project-tails">Tails</a></td> <td>Usability</td> <td>Sys Admin</td> <td>Heavy</td> <td><a href="https://tails.boum.org/chat/">#tails</a></td> </tr> <tr> <td><a href="#project-torsocks">Torsocks</a></td> <td>Usability</td> <td>C</td> <td>Light</td> <td>mwenge</td> </tr> <tr class="alt"> <td>*<a href="#project-torouter">Torouter</a></td> <td>Usability</td> <td>Sys Admin</td> <td>Light</td> <td>ioerror, Runa</td> </tr> <tr> <td><a href="#project-vidalia">Vidalia</a></td> <td>User Interface</td> <td>C++, Qt</td> <td>Light</td> <td>chiiph</td> </tr> <tr class="alt"> <td><a href="#project-arm">Arm</a></td> <td>User Interface</td> <td>Python, Curses</td> <td>Heavy</td> <td>atagar</td> </tr> <tr> <td><a href="#project-orbot">Orbot</a></td> <td>User Interface</td> <td>Java</td> <td>Moderate</td> <td>n8fr8</td> </tr> <tr class="alt"> <td><a href="#project-torbutton">Torbutton</a></td> <td>Browser Add-on</td> <td>Javascript</td> <td>Moderate</td> <td>mikeperry</td> </tr> <tr> <td>*<a href="#project-thandy">Thandy</a></td> <td>Updater</td> <td>Python</td> <td>Light</td> <td>Sebastian, Erinn, nickm</td> </tr> <tr class="alt"> <td><a href="#project-torctl">TorCtl</a></td> <td>Library</td> <td>Python</td> <td>Light</td> <td>mikeperry</td> </tr> <tr> <td><a href="#project-metrics">Metrics</a></td> <td>Client Service</td> <td>Java</td> <td>Heavy</td> <td>karsten</td> </tr> <tr class="alt"> <td><a href="#project-torstatus">TorStatus</a></td> <td>Client Service</td> <td>PHP</td> <td>None</td> <td></td> </tr> <tr> <td><a href="#project-weather">Weather</a></td> <td>Client Service</td> <td>Python</td> <td>Light</td> <td>kaner</td> </tr> <tr class="alt"> <td><a href="#project-gettor">GetTor</a></td> <td>Client Service</td> <td>Python</td> <td>Light</td> <td>kaner</td> </tr> <tr> <td><a href="#project-torcheck">TorCheck</a></td> <td>Client Service</td> <td>Python, Perl</td> <td>None</td> <td></td> </tr> <tr class="alt"> <td><a href="#project-bridgedb">BridgeDB</a></td> <td>Backend Service</td> <td>Python</td> <td>Moderate</td> <td>kaner, nickm</td> </tr> <tr> <td><a href="#project-torflow">TorFlow</a></td> <td>Backend Service</td> <td>Python</td> <td>Light</td> <td>mikeperry</td> </tr> <tr class="alt"> <td>*<a href="#project-torbel">TorBEL</a></td> <td>Backend Service</td> <td>Python</td> <td>None</td> <td>Sebastian</td> </tr> </table> <sub> * Project is still in an alpha state. </sub> <br /><br /> <a id="project-tor"></a> <h3>Tor (<a href="https://gitweb.torproject.org/tor.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Tor+Client&component=Tor+Relay&component=vidalia&order=priority">bug tracker</a>)</h3> <p> Central project, providing the core software for using and participating in the Tor network. Numerous people contribute to the project to varying extents, but the chief architects are Nick Mathewson and Roger Dingledine. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#resistCensorship">Improving Tor's ability to resist censorship</a></i><br /> <i><a href="#unitTesting">Improve our unit testing process</a></i><br /> <i><a href="#simulateSlowConnections">Simulator for slow Internet connections</a></i> </p> <a id="project-jtor"></a> <h3><a href="https://github.com/brl/JTor/wiki">JTor</a> (<a href="https://github.com/brl/JTor">code</a>, <a href="https://github.com/brl/JTor/issues">bug tracker</a>)</h3> <p> Java implementation of Tor and successor to <a href="http://onioncoffee.sourceforge.net/">OnionCoffee</a>. This project isn't yet complete, and has been inactive since Fall 2010. </p> <a id="project-tbb"></a> <h3><a href="<page projects/torbrowser>">Tor Browser Bundle</a> (<a href="https://gitweb.torproject.org/torbrowser.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Tor+bundles/installation&order=priority">bug tracker</a>)</h3> <p> The Tor Browser Bundle is an easy-to-use portable package of Tor, Vidalia, and Firefox preconfigured to work together out of the box. This is actively being worked on by Erinn Clark. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#auditTBB">Audit Tor Browser Bundles for data leaks</a></i><br /> <i><a href="#usabilityTesting">Usability testing of Tor</a></i> </p> <a id="project-tails"></a> <h3><a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> (<a href="http://git.immerda.ch/?p=amnesia.git;a=summary">code</a>, <a href="https://tails.boum.org/bugs/">bug tracker</a>)</h3> <p> The Amnesic Incognito Live System is a live CD/USB distribution preconfigured so that everything is safely routed through Tor and leaves no trace on the local system. This is a merger of the Amnesia and <a href="http://www.anonymityanywhere.com/incognito/">Incognito</a> projects, and still under very active development. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#tailsStartMenu">Custom GDM3 startup menu, aka. tails-greeter</a></i><br /> <i><a href="#tailsMetadataAnonymizing">Meta-data anonymizing toolkit for file publication</a></i><br /> <i><a href="#tailsDebianLive">Improve Debian Live support for persistence</a></i> </p> <a id="project-torsocks"></a> <h3><a href="http://code.google.com/p/torsocks/">Torsocks</a> (<a href="https://gitweb.torproject.org/torsocks.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Torify&order=priority">bug tracker</a>)</h3> <p> Utility for adapting other applications to work with Tor. Development has slowed and compatibility issues remain with some platforms, but it's otherwise feature complete. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#torsocksForOSX">Make torsocks/dsocks work on OS X</a></i> </p> <a id="project-torouter"></a> <h3><a href="<wiki>doc/Torouter">Torouter</a> (<a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Torouter&order=priority">bug tracker</a>)</h3> <p> Project to provide an easy-to-use, embedded Tor instance for routers. This had high activity in late 2010, but has since been rather quiet. </p> <a id="project-vidalia"></a> <h3><a href="<page projects/vidalia>">Vidalia</a> (<a href="https://svn.torproject.org/vidalia/vidalia/trunk/">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Vidalia&order=priority">bug tracker</a>)</h3> <p> The most commonly used user interface for Tor. Matt Edman started the project in 2006 and brought it to its current stable state. Development slowed for several years, though Tomás Touceda has since taken a lead with pushing the project forward. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#vidaliaStatusEventInterface">Tor Controller Status Event Interface for Vidalia</a></i><br /> <i><a href="#vidaliaNetworkMap">An Improved and More Usable Network Map in Vidalia</a></i> </p> <a id="project-arm"></a> <h3><a href="http://www.atagar.com/arm/">Arm</a> (<a href="https://svn.torproject.org/svn/arm/trunk/">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=arm&order=priority">bug tracker</a>)</h3> <p> Command-line monitor for Tor. This has been under very active development by its author, Damian Johnson, since early 2009 to make it a better general-purpose controller for *nix environments. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#armClientMode">Client Mode Use Cases for Arm</a></i><br /> <i><a href="#armGui">GUI for Arm</a></i> </p> <a id="project-orbot"></a> <h3><a href="https://guardianproject.info/apps/orbot/">Orbot</a> (<a href="https://svn.torproject.org/svn/projects/android/trunk/Orbot/">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Orbot&order=priority">bug tracker</a>)</h3> <p> Provides Tor on the Android platform. This was under very active development up through Fall 2010, after which things have been quiet. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#orbot-torbutton">TorButton for Mobile Firefox 4 or Custom Browser on Android</a></i><br /> <i><a href="#orbot-userInterface">Build a better user interface for Orbot</a></i><br /> <i><a href="#orbot-optimisation">Core Tor mobile optimisation</a></i><br /> <i><a href="#orbot-orlibAndOutreach">Orbot integration library and community outreach</a></i> </p> <a id="project-torbutton"></a> <h3><a href="<page torbutton/index>">Torbutton</a> (<a href="https://gitweb.torproject.org/torbutton.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Torbutton&order=priority">bug tracker</a>)</h3> <p> Firefox addon that addresses many of the client-side threats to browsing the Internet anonymously. Mike has since continued to adapt it to new threats, updated versions of Firefox, and possibly <a href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-and-fingerprinting">Chrome as well</a>. </p> <p> <b>Project Ideas:</b><br /> <i><a href="#torbuttonForThunderbird">Torbutton equivalent for Thunderbird</a></i> </p> <a id="project-thandy"></a> <h3>Thandy (<a href="https://gitweb.torproject.org/thandy.git">code</a>)</h3> <p> Updater for Tor. The project began in the Summer of 2008 but wasn't completed. Recently interest in it has been rekindled and many aspects of its design (including the language it'll be in) are currently in flux. </p> <a id="project-torctl"></a> <h3>TorCtl (<a href="https://gitweb.torproject.org/pytorctl.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Torctl&order=priority">bug tracker</a>)</h3> <p> Python bindings and utilities for using the Tor control port. It has been stable for several years, with only minor revisions. </p> <a id="project-metrics"></a> <h3><a href="https://metrics.torproject.org/">Metrics</a> (code: <a href="https://gitweb.torproject.org/metrics-db.git">db</a>, <a href="https://gitweb.torproject.org/metrics-utils.git">utils</a>, <a href="https://gitweb.torproject.org/metrics-web.git">web</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Metrics&order=priority">bug tracker</a>)</h3> <p> Processing and analytics of consensus data, provided to users via the metrics portal. This has been under active development for several years by Karsten Loesing. </p> <a id="project-torstatus"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/TorStatus">TorStatus</a> (<a href="https://svn.torproject.org/svn/torstatus/trunk/">code</a>)</h3> <p> Portal providing an overview of the Tor network, and details on any of its current relays. Though very actively used, this project has been unmaintained for a long while. </p> <a id="project-weather"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/Weather">Weather</a> (<a href="https://gitweb.torproject.org/weather.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Tor+Weather&order=priority">bug tracker</a>)</h3> <p> Provides automatic notification to subscribed relay operators when their relay's unreachable. This underwent a rewrite by the <a href="http://hfoss.wesleyan.edu/">Wesleyan HFOSS team</a>, which went live in early 2011. </p> <a id="project-gettor"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/EmailAutoResponder">GetTor</a> (<a href="https://svn.torproject.org/svn/projects/gettor/">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=GetTor&order=priority">bug tracker</a>)</h3> <p> E-mail autoresponder providing Tor's packages over SMTP. This has been relatively unchanged for quite a while. </p> <a id="project-torcheck"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/TorCheck">TorCheck</a> (<a href="https://svn.torproject.org/svn/check/trunk/">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Tor+Check&order=priority">bug tracker</a>)</h3> <p> Provides a simple site for determining if the visitor is using Tor or not. This has been relatively unchanged for quite a while. </p> <a id="project-bridgedb"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/BridgeDB">BridgeDB</a> (<a href="https://gitweb.torproject.org/bridgedb.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=BridgeDB&order=priority">bug tracker</a>)</h3> <p> Backend bridge distributor, handling the various pools they're distributed in. This was actively developed until Fall of 2010. </p> <a id="project-torflow"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/TorFlow">TorFlow</a> (<a href="https://gitweb.torproject.org/torflow.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=Torflow&order=priority">bug tracker</a>)</h3> <p> Library and collection of services for actively monitoring the Tor network. These include the Bandwidth Scanners (measuring throughput of relays) and SoaT (scans for malicious or misconfigured exit nodes). SoaT was last actively developed in the Summer of 2010, and the Bandwidth Scanners a few months later. Both have been under active use since then, but development has stopped. </p> <a id="project-torbel"></a> <h3><a href="https://trac.torproject.org/projects/tor/wiki/projects/TorBulkExitlist">TorBEL</a> (<a href="https://gitweb.torproject.org/tordnsel.git">code</a>, <a href="https://trac.torproject.org/projects/tor/query?status=accepted&status=assigned&status=needs_review&status=new&status=reopened&component=TorDNSEL/TorBEL&order=priority">bug tracker</a>)</h3> <p> The Tor Bulk Exitlist provides a method of identifying if IPs belong to exit nodes or not. This is a replacement for TorDNSEL which is a stable (though unmaintained) Haskell application for this purpose. The initial version of TorBEL was started in GSOC 2010 but since then the project has been inactive. </p> <a id="Coding"></a> <a id="Summer"></a> <h2><a class="anchor" href="#Coding">Project Ideas</a></h2> <p> You may find some of these projects to be good <a href="<page about/gsoc>">Google Summer of Code 2011</a> ideas. We have labelled each idea with how useful it would be to the overall Tor project (priority), how much work we expect it would be (effort level), how much clue you should start with (skill level), and which of our <a href="<page about/corepeople>">core developers</a> would be good mentors. If one or more of these ideas looks promising to you, please <a href="<page about/contact>">contact us</a> to discuss your plans rather than sending blind applications. You may also want to propose your own project idea — which often results in the best applications. </p> <ol> <a id="auditTBB"></a> <li> <b>Audit Tor Browser Bundles for data leaks</b> <br> Priority: <i>High</i> <br> Effort Level: <i>High</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Erinn, Jacob, Andrew</i> <p>The Tor Browser Bundle incorporates Tor, Firefox, Polipo, and the Vidalia user interface (and optionally the <a href="http://pidgin.im/">Pidgin</a> Instant Messaging client). Components are pre-configured to operate in a secure way, and it has very few dependencies on the installed operating system. It has therefore become one of the most easy to use, and popular, ways to use Tor on Windows.</p> <p>This project is to identify all of the traces left behind by using a Tor Browser Bundle on Windows, Mac OS X, or Linux. Developing ways to stop, counter, or remove these traces is a final step.</p> <p>Students should be familiar with operating system analysis, application development on one or preferably all of Windows, Linux, and Mac OS X, and be comfortable with C/C++ and shell scripting.</p> <p>If you would like to help extend or do security auditing for TBB, please contact Erinn.</p> </li> <a id="firewallProbeTool"></a> <li> <b>Develop a fully automatic firewall-probing system</b> <br> Priority: <i>High</i> <br> Effort Level: <i>Medium to High</i> <br> Skill Level: <i>High</i> <br> Likely Mentors: <i>Robert Ransom, Nick, Jacob</i> <p>We would like to have a fully automatic firewall-probing system for blocking systems with no long-term state (i.e. firewalls that can examine each connection, but do not change their behaviour for future connections based on the traffic they have seen).</p> <p>Ideally, volunteers would only need to set up one or more test servers, and run the probe client program on a publicly accessible computer behind the firewall.</p> <p>The test tool should:</p> <ul> <li>generate packet captures on both ends (and send them out to the extent possible),</li> <li>cycle through all the SSL configurations we might want to test through a censorship device, and</li> <li>also test some other protocols to see whether they are allowed through the firewall (IMAP and other mail protocols, BitTorrent, DTLS, etc.).</li> </ul> </li> <a id="tailsStartMenu"></a> <li> <b>Custom GDM3 startup menu, aka. tails-greeter</b> <br> Priority: <i>High</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium to High</i> <br> Likely Mentors: <i>intrigeri, anonym</i> <p>Several major upcoming Tails features need to gather user input at startup time: bridges support, persistence, MAC address anonymization, etc.</p> <p>Existing boot menus lack the graphical widgets and generally user-friendliness needed. Hence it was decided to implement Tails startup menu in GDM3: GDM3's default login/password prompt needs to be replaced with a custom GTK+ application hereby named tails-greeter that allows the user to provide any input necessary.</p> <p>Anyone undertaking this project should be familiar with GNU/Linux and application development; no other skill is required, apart of the ability to quickly find practical answers in APIs and documentation for many technologies she knows nothing about: this challenging coding project will indeed involve getting familiar with some modern GNU/Linux Desktop technologies such as D-Bus, GNOME and GConf. Python/GTK+ is probably the best suited language for the task.</p> <p>For more information see <a href="https://tails.boum.org/todo/boot_menu/">https://tails.boum.org/todo/boot_menu/</a></p> </li> <a id="orbot-torbutton"></a> <li> <b>TorButton for Mobile Firefox 4 or Custom Browser on Android</b> <br> Priority: <i>High</i> <br> Effort Level: <i>High</i> <br> Skill Level: <i>High</i> <br> Likely Mentors: <i>Nathan (n8fr8), Jake, Mike Perry</i> <p>Initial work has been done on implementing a proxy-setting add-on for Firefox on Android (see <a href="https://github.com/guardianproject/ProxyMob">ProxyMob</a>), but a full port of TorButton needs to be done (dependent upon Firefox 4 port of TorButton). The other approach is to implement a custom "Tor Browser" based on Firefox or Webkit browser. See <a href="http://code.google.com/p/torora/wiki/Android">Torora</a> for progress on this so far.</p> </li> <a id="orbot-userInterface"></a> <li> <b>Build a better user interface for Orbot</b> <br> Priority: <i>High</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Nathan (n8fr8), Jake</i> <p>Improved home screen to show confirmation of connection (via a TorCheck API call), better statistics about data transferred (up/down), number of circuits connected, quality of connection and so on. The "Tether Wifi" Android application is a good model to follow in how it shows a realtime count of bytes transferred as well as notifications when wifi clients connect. In addition, better handling of Tor system and error messages would also be very helpful, include use of standard Android operating systems notifications. The addition of a wizard or tutorial walkthrough for novice users to explain to them exactly what is and what is not anonymized or protected would greatly improve the likelihood they will use Orbot correctly. All of this should work on the range of screens and device types now offered for Android, from 2" phone to 10" Tablet.</p> </li> <a id="resistCensorship"></a> <li> <b>Improving Tor's ability to resist censorship</b> <br> Priority: <i>Medium to High</i> <br> Effort Level: <i>Medium to High</i> <br> Skill Level: <i>High</i> <br> Likely Mentors: <i>Roger, Nick, Jake, Thomas</i> <p>The Tor 0.2.1.x series makes <a href="<svnprojects>design-paper/blocking.html">significant improvements</a> in resisting national and organizational censorship. But Tor still needs better mechanisms for some parts of its anti-censorship design.</p> <p>One huge category of work is adding features to our <a href="https://gitweb.torproject.org/bridgedb.git?a=tree">BridgeDB</a> service (Python). Tor aims to give out <a href="<page docs/bridges>">bridge relay addresses</a> to users that can't reach the Tor network directly, but there's an arms race between algorithms for distributing addresses and algorithms for gathering and blocking them. See <a href="<blog>bridge-distribution-strategies">our blog post on the topic</a> as an overview, and then look at <a href="https://lists.torproject.org/pipermail/tor-dev/2009-December/000666.html">Roger's or-dev post</a> from December 2009 for more recent thoughts — lots of design work remains.</p> <p>If you want to get more into the guts of Tor itself (C), a more minor problem we should address is that current Tors can only listen on a single address/port combination at a time. There's <a href="<specblob>proposals/118-multiple-orports.txt">a proposal to address this limitation</a> and allow clients to connect to any given Tor on multiple addresses and ports, but it needs more work.</p> <p>This project could involve a lot of research and design. One of the big challenges will be identifying and crafting approaches that can still resist an adversary even after the adversary knows the design, and then trading off censorship resistance with usability and robustness.</p> </li> <a id="geoIPUpgrade"></a> <li> <b>Improve our GeoIP file format</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium to High</i> <br> Likely Mentors: <i>Robert Ransom</i> <p>Currently, Tor bridges and relays read an entire IP->country database into memory from a text file during startup. We would like to distribute this database and store it on disk in a much more compact form, and perform IP->country lookups on it in its on-disk format if possible.</p> <p>We have <a href='https://trac.torproject.org/projects/tor/ticket/2506'>a sketch of a design</a> for a moderately optimized format for IPv4 GeoIP data; this project will involve both implementing the IPv4 format and designing and implementing a format for IPv6 GeoIP data.</p> <!--<p>Since the core of this project is researching IPv6 GeoIP data and designing the IPv6 format, this is not likely to be a good GSoC project.</p>--> </li> <a id="armClientMode"></a> <li> <b>Client Mode Use Cases for Arm</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>High</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Damian (atagar)</i> <p><a href="<page projects/arm>">Arm</a> is a Tor command line status monitor on *nix environments (Linux, Mac, and BSD). It functions much like top does, giving a CLI overlay of Tor's bandwidth usage, connections, configuration, log, etc. Thus far its design has been geared for Tor relay operators. However, this doesn't need to be the case. This project would be to expand and simplify arm to make it useful for Tor's client users too.</p> <p>This would include UI design, experimenting, and a lot of python hacking. Here's some ideas for client functionality arm could provide:</p> <ul> <li>A panel for client connections, showing each hop of the user's circuits with the ISP, country, and jurisdiction where those relays reside. Other interesting information would be the circuit's latency, how long its been around, and its possible exit ports. Some of this will be pretty tricky and require some experimentation to figure out what information can be fetched safely (for instance, scraping rdns and whois lookups could give hints about a relay's ISP, but we'd need to do it on all Tor relays to avoid leaking our connections to the resolver).</li> <li>Options to let the user request new circuits (the "New Identity" feature in Vidalia), select the exit country, etc.</li> <li>A panel showing Internet application and if their connections are being routed through Tor or not (giving a warning if there's leaks).</li> <li>The status of the bridges we're configured to use (ie, are they up?). This would include adding control port functionality to Tor for <a href="https://trac.torproject.org/projects/tor/ticket/2068">ticket 2068</a>.</li> <li>A one click option to set Tor to be a client, relay, or bridge. The goal would be to make it trivial for users to voluntarily contribute to the Tor network.</li> <li>Menus as an alternative to hotkeys to make the interface more intuitive and usable for beginners (<a href="http://gnosis.cx/publish/programming/charming_python_6.html">example</a>).</li> <li>Look at Vidalia and TorK for ideas and solicit input from the Tor community.</li> </ul> <p> More information is available in the following sections of arm's dev notes: <a href="https://trac.torproject.org/projects/tor/wiki/projects/arm#ConnectionListingExpansion">Connection Listing Expansion</a>, <a href="https://trac.torproject.org/projects/tor/wiki/projects/arm#CircuitDetails">Circuit Details</a>, and <a href="https://trac.torproject.org/projects/tor/wiki/projects/arm#ClientModeUseCases">Client Mode Use Cases</a> </p> </li> <a id="unitTesting"></a> <li> <b>Improve our unit testing process</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Nick, Erinn</i> <p>Tor needs to be tested far more thoroughly. This is a multi-part effort. To start with, our unit test coverage should rise substantially, especially in the areas outside the utility functions. This will require significant refactoring of some parts of Tor, in order to dissociate as much logic as possible from globals.</p> <p>Additionally, we need to automate our performance testing. We've got buildbot to automate our regular integration and compile testing already (though we need somebody to set it up on Windows), but we need to get our network simulation tests (as built in <a href="https://svn.torproject.org/svn/torflow/trunk/README">TorFlow</a>) updated for more recent versions of Tor, and designed to launch a test network either on a single machine, or across several, so we can test changes in performance on machines in different roles automatically.</p> </li> <a id="simulateSlowConnections"></a> <li> <b>Simulator for slow Internet connections</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Nick</i> <p> Many users of Tor have poor-quality Internet connections, giving low bandwidth, high latency, and high packet loss/re-ordering. User experience is that Tor reacts badly to these conditions, but it is difficult to improve the situation without being able to repeat the problems in the lab. </p> <p> This project would be to build a simulation environment which replicates the poor connectivity so that the effect on Tor performance can be measured. Other components would be a testing utility to establish what are the properties of connections available, and to measure the effect of performance-improving modifications to Tor. </p> <p> The tools used would be up to the student, but dummynet (for FreeBSD) and nistnet (for Linux) are two potential components on which this project could be built. Students should be experienced with network programming/debugging and TCP/IP, and preferably familiar with C and a scripting language. </p> </li> <a id="torbuttonForThunderbird"></a> <li> <b>Torbutton equivalent for Thunderbird</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>High</i> <br> Skill Level: <i>High</i> <br> Likely Mentors: <i>Mike</i> <p> We're hearing from an increasing number of users that they want to use Thunderbird with Tor. However, there are plenty of application-level concerns, for example, by default Thunderbird will put your hostname in the outgoing mail that it sends. At some point we should start a new push to build a Thunderbird extension similar to Torbutton. </p> </li> <a id="usabilityTesting"></a> <li> <b>Usability testing of Tor</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Low to Medium</i> <br> Likely Mentors: <i>Andrew</i> <p> Especially the browser bundle, ideally amongst our target demographic. That would help a lot in knowing what needs to be done in terms of bug fixes or new features. We get this informally at the moment, but a more structured process would be better. </p> <p> Please note that since this isn't a coding project, it isn't suitable for Google Summer of Code. </p> </li> <a id="tailsMetadataAnonymizing"></a> <li> <b>Meta-data anonymizing toolkit for file publication</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Low to Medium</i> <br> Skill Level: <i>Low to Medium</i> <br> Likely Mentors: <i>intrigeri, anonym</i> <p>Tor helps greatly in publishing files anonymously. However, much personal information can be enclosed *inside* such published files' meta-data: GPS coordinates, author's name and so on. Anyone who wants to anonymously publish a file can thus far too easily de-anonymize herself.</p> <p>A set of tools allowing users to easily inspect and clean up meta-data in files would benefit Tor users, and would e.g. be shipped in Tails.</p> <p>A graphical user interface is a must, but library and command-line interfaces are most welcome so that future work can add support for cleaning published files to various publishing tools, such as desktop social networking clients and Web content management systems.</p> <p>This project mostly consists of writing glue between the many existing tools and libraries that provide read/write access to files' meta-data. An extensible program design would probably be the best bet, so that support for other kinds of files can easily be added later.</p> <p>The meta-data cleaning toolkit would run at least on GNU/Linux; additional Windows and/or Mac OS X support would be welcome. The tools used would be up to the students. The detailed specification is ready and will be published soon.</p> </li> <a id="tailsDebianLive"></a> <li> <b>Improve Debian Live support for persistence</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Low to Medium</i> <br> Likely Mentors: <i>intrigeri, anonym</i> <p>Data persistence is a somewhat tricky topic in a Live system context, especially one such as Tails, which is explicitly designed to avoid leaving any trace of its use.</p> <p>Some real-life use cases, however, require some kind of data persistence. To start with, Tails should (carefully) support persistence of application-specific configurations (e.g. GnuPG keyring) and of a user arbitrary data store. Note that persistence in Tails will always be opt-in and require encrypted storage.</p> <p>The backend work consists of improving Debian Live's existing persistence features to make them suit the specific context of Tails. A trust relationship is already established with upstream who is happy to merge our changes. The codebase is not that small and much refactoring is needed, so this really is a programming project rather than a fire'n'forget shell script hack contest.</p> <p>Anyone undertaking this project must be familiar with GNU/Linux, and preferably with Debian. Being able to (quickly learn to) write clean and safe programs in shell is also needed.</p> <p>For more information, see <a href="https://tails.boum.org/todo/persistence/">https://tails.boum.org/todo/persistence/</a>.</p> </li> <a id="torsocksForOSX"></a> <li> <b>Make torsocks/dsocks work on OS X</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Robert Hogan</i> <p> <a href="https://code.google.com/p/torsocks/">Torsocks</a> and <a href="https://code.google.com/p/dsocks/">dsocks</a> are wrappers that will run applications, intercept their outgoing network connections, and push those connections through Tor. The goal is to handle applications that don't support proxies (or don't supporting them well). To get it right, they need to intercept many system calls. The syscalls you need to intercept on Linux differ dramatically from those on BSD. So Torsocks works fine on Linux, dsocks works ok on BSD (though it may be less maintained and thus might miss more syscalls), and nothing works well on both. First, we should patch dsocks to use Tor's <i>mapaddress</i> commands from the controller interface, so we don't waste a whole round-trip inside Tor doing the resolve before connecting. Second, we should make our <i>torify</i> script detect which of torsocks or dsocks is installed, and call them appropriately. This probably means unifying their interfaces, and might involve sharing code between them or discarding one entirely. </p> </li> <a id="vidaliaStatusEventInterface"></a> <li> <b>Tor Controller Status Event Interface for Vidalia</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Low to Medium</i> <br> Likely Mentors: <i>Tomás</i> <p>There are a number of status changes inside Tor of which the user may need to be informed. For example, if the user is trying to set up his Tor as a relay and Tor decides that its ports are not reachable from outside the user's network, we should alert the user. Currently, all the user gets is a couple of log messages in Vidalia's 'message log' window, which they likely never see since they don't receive a notification that something has gone wrong. Even if the user does actually look at the message log, most of the messages make little sense to the novice user.</p> <p>Tor has the ability to inform Vidalia of many such status changes, and we recently implemented support for a couple of these events. Still, there are many more status events which the user should be informed of, and we need a better UI for actually displaying them to the user.</p> <p>The goal of this project then is to design and implement a UI for displaying Tor status events to the user. For example, we might put a little badge on Vidalia's tray icon that alerts the user to new status events they should look at. Double-clicking the icon could bring up a dialog that summarizes recent status events in simple terms and maybe suggests a remedy for any negative events if they can be corrected by the user. Of course, this is just an example and one is free to suggest another approach.</p> <p>A person undertaking this project should have good UI design and layout skills and some C++ development experience. Previous experience with Qt and Qt's Designer will be very helpful, but are not required. Some English writing ability will also be useful, since this project will likely involve writing small amounts of help documentation that should be understandable by non-technical users. Bonus points for some graphic design/Photoshop fu, since we might want/need some shiny new icons too.</p> </li> <a id="orbot-optimisation"></a> <li> <b>Core Tor mobile optimisation</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>High</i> <br> Likely Mentors: <i>Nathan (n8fr8), Jake</i> <p> The existing port of Tor to Android is basically a straight cross-compile to Linux ARM. There has been no work done in looking at possible optimizations of Tor within a mobile hardware environment or on mobile networks. In addition, a number of additional Android OS APIs are available (such as wireless network status) that could be taken advantage of. </p> <p> It should be noted, that even without optimisation, Tor is handling the mobile network environment very well, automatically detecting change in IP addresses, opening circuits, etc, as the device switches from no coverage to 2G, 3G or Wifi constantly as it changes position. However, this observation of "very well", is just based on user experience, and not any detailed study of what exactly is happening, and what threats might exist because of this constantly changing network state. </p> <p> Finally, the build process needs to be moved to the Android NDK from the custom GCC toolchain we are now using, and compatibility with Android 2.3 and 3.x Honeycomb OS need to be verified. </p> <p> For more information see the <a href="https://svn.torproject.org/svn/projects/android/trunk/Orbot/BUILD">Orbot build documentation</a>. </p> </li> <a id="orbot-orlibAndOutreach"></a> <li> <b>Orbot integration library and community outreach</b> <br> Priority: <i>Medium</i> <br> Effort Level: <i>Low</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Nathan (n8fr8)</i> <p> We need additional work on <a href="https://github.com/guardianproject/orlib">ORLib</a>, our library for use with third-party application to easily enable them to support "Torification" on non-rooted devices (i.e. w/o transparent proxying). This library includes a SOCKS client, a wrapper for the Apache HTTPClient library, a utility class for detecting the state of Orbot connectivity, and other relevant/useful things an Android app might need to anonymize itself. This work would includes direct development of the library, documentation, and sample code. Outreach or effort to implement the library within other open-source apps is also needed. </p> </li> <a id="vidaliaNetworkMap"></a> <li> <b>An Improved and More Usable Network Map in Vidalia</b> <br> Priority: <i>Low to Medium</i> <br> Effort Level: <i>Medium</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Tomás</i> <p> One of Vidalia's existing features is a network map that shows the user the approximate geographic location of relays in the Tor network and plots the paths the user's traffic takes as it is tunneled through the Tor network. The map is currently not very interactive and has rather poor graphics. Instead, we implemented KDE's Marble widget such that it gives us a better quality map and enables improved interactivity, such as allowing the user to click on individual relays or circuits to display additional information. We want to add the ability for users to click on a particular relay or a country containing one or more Tor exit relays and say, "I want my connections to exit from here." </p> <p> This project will first involve getting familiar with Vidalia and the Marble widget's API. One will then integrate the widget into Vidalia and customize Marble to be better suited for our application, such as making circuits clickable, storing cached map data in Vidalia's own data directory, and customizing some of the widget's dialogs. </p> <p> A person undertaking this project should have good C++ development experience. Previous experience with Qt and CMake is helpful, but not required. </p> </li> <a id="armGui"></a> <li> <b>GUI for Arm</b> <br> Priority: <i>Low</i> <br> Effort Level: <i>High</i> <br> Skill Level: <i>Medium</i> <br> Likely Mentors: <i>Damian (atagar)</i> <p> Arm has several unique features, some of the most interesting being its connection listing (correlating netstat results against the Tor consensus) and configuration editor (a quick method for editing Tor's config, with information pulled from the control port and man page). However, since arm is a command line controller it's of limited appeal to certain sets of users. This project would be to build a GTK or Qt frontend for the controller, providing similar features set but with a windowed interface. </p> <p> The vast majority of arm's more interesting functionality lies in its backend <a href="https://svn.torproject.org/svn/arm/trunk/src/util/">utilities</a>, so there should be little to no work decoupling the CLI from its backend. Instead, this project would mostly be UI hacking and experimentation, trying different interfaces to find something that's elegant and simple, but matches the information found in the current terminal application. </p> </li> <li> <b>Bring up new ideas!</b> <br> Don't like any of these? Look at the <a href="/press/presskit/2008-12-19-roadmap-full.pdf">Tor development roadmap</a> for more ideas, or just try out Tor, Vidalia, and Torbutton, and find out what you think needs fixing. Some of the <a href="<spectree>proposals">current proposals</a> might also be short on developers. </li> </ol> <a id="OtherCoding"></a> <h2><a class="anchor" href="#OtherCoding">Other Coding and Design related ideas</a></h2> <ol> <li>Tor relays don't work well on Windows XP. On Windows, Tor uses the standard <tt>select()</tt> system call, which uses space in the non-page pool. This means that a medium sized Tor relay will empty the non-page pool, <a href="<wiki>doc/WindowsBufferProblems">causing havoc and system crashes</a>. We should probably be using overlapped IO instead. One solution would be to teach <a href="http://www.monkey.org/~provos/libevent/">libevent</a> how to use overlapped IO rather than select() on Windows, and then adapt Tor to the new libevent interface. Christian King made a <a href="https://svn.torproject.org/svn/libevent-urz/trunk/">good start</a> on this in the summer of 2007.</li> <li>We need to actually start building our <a href="<page docs/documentation>#DesignDoc">blocking-resistance design</a>. This involves fleshing out the design, modifying many different pieces of Tor, adapting <a href="<page projects/vidalia>">Vidalia</a> so it supports the new features, and planning for deployment.</li> <li>We need a flexible simulator framework for studying end-to-end traffic confirmation attacks. Many researchers have whipped up ad hoc simulators to support their intuition either that the attacks work really well or that some defense works great. Can we build a simulator that's clearly documented and open enough that everybody knows it's giving a reasonable answer? This will spur a lot of new research. See the entry <a href="#Research">below</a> on confirmation attacks for details on the research side of this task — who knows, when it's done maybe you can help write a paper or three also.</li> <li>Tor 0.1.1.x and later include support for hardware crypto accelerators via OpenSSL. It has been lightly tested and is possibly very buggy. We're looking for more rigorous testing, performance analysis, and optimally, code fixes to OpenSSL and Tor if needed.</li> <li>Perform a security analysis of Tor with <a href="https://secure.wikimedia.org/wikipedia/en/wiki/Fuzz_testing">"fuzz"</a>. Determine if there are good fuzzing libraries out there for what we want. Win fame by getting credit when we put out a new release because of you!</li> <li>Tor uses TCP for transport and TLS for link encryption. This is nice and simple, but it means all cells on a link are delayed when a single packet gets dropped, and it means we can only reasonably support TCP streams. We have a <a href="<page docs/faq>#TransportIPnotTCP">list of reasons why we haven't shifted to UDP transport</a>, but it would be great to see that list get shorter. We also have a proposed <a href="<specblob>proposals/100-tor-spec-udp.txt">specification for Tor and UDP</a> — please let us know what's wrong with it.</li> <li>We're not that far from having IPv6 support for destination addresses (at exit nodes). If you care strongly about IPv6, that's probably the first place to start.</li> <li>We need a way to generate the website diagrams (for example, the "How Tor Works" pictures on the <a href="<page about/overview>">overview page</a> from source, so we can translate them as UTF-8 text rather than edit them by hand with Gimp. We might want to integrate this as an wml file so translations are easy and images are generated in multiple languages whenever we build the website.</li> <li>How can we make the various LiveCD/USB systems easier to maintain, improve, and document? One example is <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a>. </li> <li> Another anti-censorship project is to try to make Tor more scanning-resistant. Right now, an adversary can identify <a href="<specblob>proposals/125-bridges.txt">Tor bridges</a> just by trying to connect to them, following the Tor protocol, and seeing if they respond. To solve this, bridges could <a href="<svnprojects>design-paper/blocking.html#tth_sEc9.3">act like webservers</a> (HTTP or HTTPS) when contacted by port-scanning tools, and not act like bridges until the user provides a bridge-specific key. To start, check out Shane Pope's <a href="http://dl.dropbox.com/u/37735/index.html">thesis and prototype</a>. </li> </ol> <a id="Research"></a> <h2><a class="anchor" href="#Research">Research</a></h2> <ol> <li>The "end-to-end traffic confirmation attack": by watching traffic at Alice and at Bob, we can <a href="http://freehaven.net/anonbib/#danezis:pet2004">compare traffic signatures and become convinced that we're watching the same stream</a>. So far Tor accepts this as a fact of life and assumes this attack is trivial in all cases. First of all, is that actually true? How much traffic of what sort of distribution is needed before the adversary is confident he has won? Are there scenarios (e.g. not transmitting much) that slow down the attack? Do some traffic padding or traffic shaping schemes work better than others?</li> <li>A related question is: Does running a relay/bridge provide additional protection against these timing attacks? Can an external adversary that can't see inside TLS links still recognize individual streams reliably? Does the amount of traffic carried degrade this ability any? What if the client-relay deliberately delayed upstream relayed traffic to create a queue that could be used to mimic timings of client downstream traffic to make it look like it was also relayed? This same queue could also be used for masking timings in client upstream traffic with the techniques from <a href="http://www.freehaven.net/anonbib/#ShWa-Timing06">adaptive padding</a>, but without the need for additional traffic. Would such an interleaving of client upstream traffic obscure timings for external adversaries? Would the strategies need to be adjusted for asymmetric links? For example, on asymmetric links, is it actually possible to differentiate client traffic from natural bursts due to their asymmetric capacity? Or is it easier than symmetric links for some other reason?</li> <li>Repeat Murdoch and Danezis's <a href="http://www.cl.cam.ac.uk/~sjm217/projects/anon/#torta">attack from Oakland 05</a> on the current Tor network. See if you can learn why it works well on some nodes and not well on others. (My theory is that the fast nodes with spare capacity resist the attack better.) If that's true, then experiment with the RelayBandwidthRate and RelayBandwidthBurst options to run a relay that is used as a client while relaying the attacker's traffic: as we crank down the RelayBandwidthRate, does the attack get harder? What's the right ratio of RelayBandwidthRate to actually capacity? Or is it a ratio at all? While we're at it, does a much larger set of candidate relays increase the false positive rate or other complexity for the attack? (The Tor network is now almost two orders of magnitude larger than it was when they wrote their paper.) Be sure to read <a href="http://freehaven.net/anonbib/#clog-the-queue">Don't Clog the Queue</a> too.</li> <li>The "routing zones attack": most of the literature thinks of the network path between Alice and her entry node (and between the exit node and Bob) as a single link on some graph. In practice, though, the path traverses many autonomous systems (ASes), and <a href="http://freehaven.net/anonbib/#feamster:wpes2004">it's not uncommon that the same AS appears on both the entry path and the exit path</a>. Unfortunately, to accurately predict whether a given Alice, entry, exit, Bob quad will be dangerous, we need to download an entire Internet routing zone and perform expensive operations on it. Are there practical approximations, such as avoiding IP addresses in the same /8 network?</li> <li>Other research questions regarding geographic diversity consider the tradeoff between choosing an efficient circuit and choosing a random circuit. Look at Stephen Rollyson's <a href="http://swiki.cc.gatech.edu:8080/ugResearch/uploads/7/ImprovingTor.pdf">position paper</a> on how to discard particularly slow choices without hurting anonymity "too much". This line of reasoning needs more work and more thinking, but it looks very promising.</li> <li>Tor doesn't work very well when relays have asymmetric bandwidth (e.g. cable or DSL). Because Tor has separate TCP connections between each hop, if the incoming bytes are arriving just fine and the outgoing bytes are all getting dropped on the floor, the TCP push-back mechanisms don't really transmit this information back to the incoming streams. Perhaps Tor should detect when it's dropping a lot of outgoing packets, and rate-limit incoming streams to regulate this itself? I can imagine a build-up and drop-off scheme where we pick a conservative rate-limit, slowly increase it until we get lost packets, back off, repeat. We need somebody who's good with networks to simulate this and help design solutions; and/or we need to understand the extent of the performance degradation, and use this as motivation to reconsider UDP transport.</li> <li>A related topic is congestion control. Is our current design sufficient once we have heavy use? Maybe we should experiment with variable-sized windows rather than fixed-size windows? That seemed to go well in an <a href="http://www.psc.edu/networking/projects/hpn-ssh/theory.php">ssh throughput experiment</a>. We'll need to measure and tweak, and maybe overhaul if the results are good.</li> <li>Our censorship-resistance goals include preventing an attacker who's looking at Tor traffic on the wire from <a href="<svnprojects>design-paper/blocking.html#sec:network-fingerprint">distinguishing it from normal SSL traffic</a>. Obviously we can't achieve perfect steganography and still remain usable, but for a first step we'd like to block any attacks that can win by observing only a few packets. One of the remaining attacks we haven't examined much is that Tor cells are 512 bytes, so the traffic on the wire may well be a multiple of 512 bytes. How much does the batching and overhead in TLS records blur this on the wire? Do different buffer flushing strategies in Tor affect this? Could a bit of padding help a lot, or is this an attack we must accept?</li> <li>Tor circuits are built one hop at a time, so in theory we have the ability to make some streams exit from the second hop, some from the third, and so on. This seems nice because it breaks up the set of exiting streams that a given relay can see. But if we want each stream to be safe, the "shortest" path should be at least 3 hops long by our current logic, so the rest will be even longer. We need to examine this performance / security tradeoff.</li> <li>It's not that hard to DoS Tor relays or directory authorities. Are client puzzles the right answer? What other practical approaches are there? Bonus if they're backward-compatible with the current Tor protocol.</li> <li>Programs like <a href="<page torbutton/index>">Torbutton</a> aim to hide your browser's UserAgent string by replacing it with a uniform answer for every Tor user. That way the attacker can't splinter Tor's anonymity set by looking at that header. It tries to pick a string that is commonly used by non-Tor users too, so it doesn't stand out. Question one: how badly do we hurt ourselves by periodically updating the version of Firefox that Torbutton claims to be? If we update it too often, we splinter the anonymity sets ourselves. If we don't update it often enough, then all the Tor users stand out because they claim to be running a quite old version of Firefox. The answer here probably depends on the Firefox versions seen in the wild. Question two: periodically people ask us to cycle through N UserAgent strings rather than stick with one. Does this approach help, hurt, or not matter? Consider: cookies and recognizing Torbutton users by their rotating UserAgents; malicious websites who only attack certain browsers; and whether the answers to question one impact this answer. </li> <li>How many bridge relays do you need to know to maintain reachability? We should measure the churn in our bridges. If there is lots of churn, are there ways to keep bridge users more likely to stay connected? </li> </ol> <p> <a href="<page about/contact>">Let us know</a> if you've made progress on any of these! </p> </div> <!-- END MAINCOL --> <div id = "sidecol"> #include "side.wmi" #include "info.wmi" </div> <!-- END SIDECOL --> </div> <!-- END CONTENT --> #include <foot.wmi>