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     <a href="<page index>">Home &raquo; </a>
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     <a href="<page docs/documentation>">Documentation &raquo; </a>
     <a href="<page docs/faq>">FAQ</a>
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     <h1>Tor FAQ</h1>
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     <hr>
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     <p>General questions:</p>
     <ul>
     <li><a href="#WhatIsTor">What is Tor?</a></li>
     <li><a href="#Torisdifferent">How is Tor different from other proxies?</a></li>
     <li><a href="#CompatibleApplications">What programs can I use with
     Tor?</a></li>
     <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
     <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
     <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
     CD?</a></li>
     <li><a href="#SupportMail">How can I get an answer to my
     Tor support mail?</a></li>
     <li><a href="#WhySlow">Why is Tor so slow?</a></li>
     <li><a href="#Funding">What would The Tor Project do with more
     funding?</a></li>
     </ul>
     
     <p>Compilation and Installation:</p>
     <ul>
     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
     <li><a href="#PGPSigs">What are these "sig" files on the download
     page?</a></li>
     <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>
     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
     have a virus or spyware?</a></li>
     <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</a></li>
     </ul>
     
     <p>Running Tor:</p>
     
     <p>Running a Tor client:</p>
     <ul>
     <li><a href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></li>
     </ul>
     
     <p>Running a Tor relay:</p>
     <ul>
     <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>
     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal
     with abuse issues.</a></li>
     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
     relay?</a></li>
     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?</a></li>
     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>
     </ul>
     
     <p>Running a Tor hidden service:</p>
     
     <p>Anonymity and Security:</p>
     <ul>
     <li><a href="#KeyManagement">Tell me about all the keys Tor uses.</a></li>
     </ul>
     
     <p>Alternate designs that we don't do (yet):</p>
     <ul>
     <li><a href="#EverybodyARelay">You should make every Tor user be a
     relay.</a></li>
     </ul>
     
     <p>Abuse</p>
     <ul>
     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
     <li><a href="#RespondISP">How do I respond to my ISP about my exit
     relay?</a></li>
     </ul>
     
     <p>For other questions not yet on this version of the FAQ, see the <a
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     href="<wikifaq>">wiki FAQ</a> for now.</p>
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     <a id="General"></a>
     
     <a id="WhatIsTor"></a>
     <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
     
     <p>
     The name "Tor" can refer to several different components.
     </p>
     
     <p>
     The Tor software is a program you can run on your computer that helps keep
     you safe on the Internet. Tor protects you by bouncing your communications
     around a distributed network of relays run by volunteers all around
     the world: it prevents somebody watching your Internet connection from
     learning what sites you visit, and it prevents the sites you visit
     from learning your physical location. This set of volunteer relays is
     called the Tor network. You can read more about how Tor works on the <a
     href="<page about/overview>">overview page</a>.
     </p>
     
     <p>
     The Tor Project is a non-profit (charity) organization that maintains
     and develops the Tor software.
     </p>
     
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     <a id="Torisdifferent"></a>
     <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
     <p>
     A typical proxy provider sets up a server somewhere on the Internet and allows you to use it to relay your traffic.  This creates a simple, easy to maintain architecture.  The users all enter and leave through the same server.  The provider may charge for use of the proxy, or fund their costs through advertisements on the server.  In the simplest configuration, you don't have to install anything.  You just have to point your browser at their proxy server.  Simple proxy providers are fine solutions if you do not want protections for your privacy and anonymity online and you trust the provider from doing bad things.  Some simple proxy providers use SSL to secure your connection to them.  This may protect you against local eavesdroppers, such as those at a cafe with free wifi Internet.
     </p>
     <p>
     Simple proxy providers also create a single point of failure.  The provider knows who you are and where you browse on the Internet.  They can see your traffic as it passes through their server.  In some cases, they can see your encrypted traffic as they relay it to your banking site or to ecommerce stores.  You have to trust the provider isn't doing any number of things, such as watching your traffic, injecting their own advertisements into your traffic stream, and isn't recording your personal details.
     </p>
     <p>
     Tor passes your traffic through at least 3 different servers before sending it on to the destination.  Tor does not modify, or even know, what you are sending into it.  It merely relays your traffic, completely encrypted through the Tor network and has it pop out somewhere else in the world, completely intact.  The Tor client is required because we assume you trust your local computer.  The Tor client manages the encryption and the path chosen through the network.  The relays located all over the world merely pass encrypted packets between themselves.</p>
     <p>
     <dl>
     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad first of three servers can see encrypted Tor traffic coming from your computer.  It still doesn't know who you are and what you are doing over Tor.  It merely sees "This IP address is using Tor".  Tor is not illegal anywhere in the world, so using Tor by itself is fine.  You are still protected from this node figuring out who you are and where you are going on the Internet.</dd>
     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad third of three servers can see the traffic you sent into Tor.  It won't know who sent this traffic.  If you're using encryption, such as visiting a bank or e-commerce website, or encrypted mail connections, etc, it will only know the destination.  It won't be able to see the data inside the traffic stream.  You are still protected from this node figuring out who you are and if using encryption, what data you're sending to the destination.</dd>
     </dl>
     </p>
     
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     <a id="CompatibleApplications"></a>
     <h3><a class="anchor" href="#CompatibleApplications">What programs can
     I use with Tor?</a></h3>
     
     <p>
     There are two pieces to "Torifying" a program: connection-level anonymity
     and application-level anonymity. Connection-level anonymity focuses on
     making sure the application's Internet connections get sent through Tor.
     This step is normally done by configuring
     the program to use your Tor client as a "socks" proxy, but there are
     other ways to do it too. For application-level anonymity, you need to
     make sure that the information the application sends out doesn't hurt
     your privacy. (Even if the connections are being routed through Tor, you
     still don't want to include sensitive information like your name.) This
     second step needs to be done on a program-by-program basis, which is
     why we don't yet recommend very many programs for safe use with Tor.
     </p>
     
     <p>
     Most of our work so far has focused on the Firefox web browser. The
     bundles on the <a href="<page download/download>">download page</a> automatically
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     install the <a href="<page torbutton/index>">Torbutton Firefox
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     extension</a> if you have Firefox installed. As of version 1.2.0,
     Torbutton now takes care of a lot of the connection-level and
     application-level worries.
     </p>
     
     <p>
     There are plenty of other programs you can use with Tor,
     but we haven't researched the application-level anonymity
     issues on them well enough to be able to recommend a safe
     configuration. Our wiki has a list of instructions for <a
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     href="<wiki>TheOnionRouter/TorifyHOWTO">Torifying
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     specific applications</a>. There's also a <a
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     href="<wiki>TheOnionRouter/SupportPrograms">list
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     of applications that help you direct your traffic through Tor</a>.
     Please add to these lists and help us keep them accurate!
     </p>
     
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     <a id="WhyCalledTor"></a>
     <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
     
     <p>
     Because Tor is the onion routing network. When we were starting the
     new next-generation design and implementation of onion routing in
     2001-2002, we would tell people we were working on onion routing,
     and they would say "Neat. Which one?" Even if onion routing has
     become a standard household term, Tor was born out of the actual <a
     href="http://www.onion-router.net/">onion routing project</a> run by
     the Naval Research Lab.
     </p>
     
     <p>
     (It's also got a fine translation from German and Turkish.)
     </p>
     
     <p>
     Note: even though it originally came from an acronym, Tor is not spelled
     "TOR". Only the first letter is capitalized. In fact, we can usually
     spot people who haven't read any of our website (and have instead learned
     everything they know about Tor from news articles) by the fact that they
     spell it wrong.
     </p>
     
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     <a id="Backdoor"></a>
     <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
     
     <p>
     There is absolutely no backdoor in Tor. Nobody has asked us to put one
     in, and we know some smart lawyers who say that it's unlikely that anybody
     will try to make us add one in our jurisdiction (U.S.). If they do
     ask us, we will fight them, and (the lawyers say) probably win.
     </p>
     
     <p>
     We think that putting a backdoor in Tor would be tremendously
     irresponsible to our users, and a bad precedent for security software
     in general. If we ever put a deliberate backdoor in our security
     software, it would ruin our professional reputations. Nobody would
     trust our software ever again &mdash; for excellent reason!
     </p>
     
     <p>
     But that said, there are still plenty of subtle attacks
     people might try. Somebody might impersonate us, or break into our
     computers, or something like that. Tor is open source, and you should
     always check the source (or at least the diffs since the last release)
     for suspicious things. If we (or the distributors) don't give you
     source, that's a sure sign something funny might be going on. You
     should also check the <a href="<page docs/verifying-signatures>">PGP
     signatures</a> on the releases, to make sure nobody messed with the
     distribution sites.
     </p>
     
     <p>
     Also, there might be accidental bugs in Tor that could affect your
     anonymity. We periodically find and fix anonymity-related bugs, so make
     sure you keep your Tor versions up-to-date.
     </p>
     
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     <a id="DistributingTor"></a>
     <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on
     my magazine's CD?</a></h3>
     
     <p>
     Yes.
     </p>
     
     <p>
     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
     means we give you the rights to redistribute the Tor software, either
     modified or unmodified, either for a fee or gratis. You don't have to
     ask us for specific permission.
     </p>
     
     <p>
     However, if you want to redistribute the Tor software you must follow our
     <a href="<gitblob>LICENSE">LICENSE</a>.
     Essentially this means that you need to include our LICENSE file along
     with whatever part of the Tor software you're distributing.
     </p>
     
     <p>
     Most people who ask us this question don't want to distribute just the
     Tor software, though. They want to distribute the Tor bundles, which
     typically include <a href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>
     and <a href="<page projects/vidalia>">Vidalia</a>.
     You will need to follow the licenses for those programs
     as well. Both of them are distributed under the <a
     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General
     Public License</a>. The simplest way to obey their licenses is to
     include the source code for these programs everywhere you include
     the bundles themselves. Look for "source" packages on the <a
     href="<page projects/vidalia>">Vidalia page</a> and the <a
     href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo
     download page</a>.
     </p>
     
     <p>
     Also, you should make sure not to confuse your readers about what Tor is,
     who makes it, and what properties it provides (and doesn't provide). See
     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for details.
     </p>
     
     <p>
     Lastly, you should realize that we release new versions of the
     Tor software frequently, and sometimes we make backward incompatible
     changes. So if you distribute a particular version of the Tor software, it
     may not be supported &mdash; or even work &mdash; six months later. This
     is a fact of life for all security software under heavy development.
     </p>
     
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     <a id="SupportMail"></a>
     <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
     Tor support mail?</a></h3>
     
     <p>
     Many people send the Tor developers mail privately, or send mail to
     our internal <a href="<page about/contact>">lists</a>, with questions about their
     specific setup &mdash; they can't get their firewall working right,
     they can't configure Polipo correctly, or so on. Sometimes our
     volunteers can answer these mails, but typically they need to spend
     most of their time on development tasks that will benefit more people.
     This is especially true if your question is already covered in the <a
     href="<page docs/documentation>">documentation</a> or on this FAQ.
     </p>
     
     <p>
     So if we don't answer your mail, first check the <a href="<page
     docs/documentation>">documentation</a> page, along with this FAQ,
     to make sure your question isn't already answered.  Then read <a
     href="http://www.catb.org/~esr/faqs/smart-questions.html">"How to ask
     questions the smart way"</a>. If this doesn't help you, note that we
     have <a href="<page docs/documentation>#Support">an IRC channel</a> where you
     can ask your questions (but if they are still open-ended, ill-formed,
     or not about Tor, you likely won't get much help there either). Lastly,
     people on the <a href="<page docs/documentation>#MailingLists">or-talk
     mailing list</a> may be able to provide some hints for you, if
     others have experienced your problems too. Be sure to look over <a
     href="http://archives.seul.org/or/talk/">the archives</a> first.
     </p>
     
     <p>
     Another strategy is to <a href="<page docs/tor-doc-relay>">run a Tor
     relay for a while</a>, and/or <a href="<page donate/donate>">donate money</a>
     <a href="<page getinvolved/volunteer>">or time</a> to the effort. We're more likely
     to pay attention to people who have demonstrated interest and commitment
     to giving back to the Tor community.
     </p>
     
     <p>
     If you find your answer, please stick around on the IRC channel or the
     mailing list and answer questions from others.
     </p>
     
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     <a id="WhySlow"></a>
     <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
     
     <p>
     There are many reasons why the Tor network is currently slow.
     </p>
     
     <p>
     Before we answer, though, you should realize that Tor is never going to
     be blazing fast. Your traffic is bouncing through volunteers' computers
     in various parts of the world, and some bottlenecks and network latency
     will always be present. You shouldn't expect to see university-style
     bandwidth through Tor.
     </p>
     
     <p>
     But that doesn't mean that it can't be improved. The current Tor network
     is quite small compared to the number of people trying to use it, and
     many of these users don't understand or care that Tor can't currently
     handle file-sharing traffic load.
     </p>
     
     <p>
     For the much more in-depth answer, see <a
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     href="<blog>why-tor-is-slow">Roger's blog
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     post on the topic</a>, which includes both a detailed PDF and a video
     to go with it.
     </p>
     
     <p>
     What can you do to help?
     </p>
     
     <ul>
     
     <li>
     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
     for others</a>. Help make the Tor network large enough that we can handle
     all the users who want privacy and security on the Internet.
     </li>
     
     <li>
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     <a href="<page projects/vidalia>">Help us make Tor more usable</a>. We
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     especially need people to help make it easier to configure your Tor
     as a relay. Also, we need help with clear simple documentation to
     walk people through setting it up.
     </li>
     
     <li>
     There are some bottlenecks in the current Tor network. Help us design
     experiments to track down and demonstrate where the problems are, and
     then we can focus better on fixing them.
     </li>
     
     <li>
     There are some steps that individuals
     can take to improve their Tor performance. <a
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     href="<wiki>TheOnionRouter/FireFoxTorPerf">You
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     can configure your Firefox to handle Tor better</a>, <a
     href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
     Polipo with Tor</a>, or you can try <a href="<page download/download>">upgrading
     to the latest version of Tor</a>.  If this works well, please help by
     documenting what you did, and letting us know about it.
     </li>
     
     <li>
     Tor needs some architectural changes too. One important change is to
     start providing <a href="#EverybodyARelay">better service to people who
     relay traffic</a>. We're working on this, and we'll finish faster if we
     get to spend more time on it.
     </li>
     
     <li>
     Help do other things so we can do the hard stuff. Please take a moment
     to figure out what your skills and interests are, and then <a href="<page
     getinvolved/volunteer>">look at our volunteer page</a>.
     </li>
     
     <li>
     Help find sponsors for Tor. Do you work at a company or government agency
     that uses Tor or has a use for Internet privacy, e.g. to browse the
     competition's websites discreetly, or to connect back to the home servers
     when on the road without revealing affiliations? If your organization has
     an interest in keeping the Tor network working, please contact them about
     supporting Tor. Without sponsors, Tor is going to become even slower.
     </li>
     
     <li>
     If you can't help out with any of the above, you can still help out
     individually by <a href="<page donate/donate>">donating a bit of money to the
     cause</a>. It adds up!
     </li>
     
     </ul>
     
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     <a id="Funding"></a>
     <h3><a class="anchor" href="#Funding">What would The Tor Project do with
     more funding?</a></h3>
     
     <p>
     We have about 1800 relays right now, pushing over 150 MB/s average
     traffic. We have several hundred thousand active users. But the Tor
     network is not yet self-sustaining.
     </p>
     
     <p>
     There are six main development/maintenance pushes that need attention:
     </p>
     
     <ul>
     
     <li>
     Scalability: We need to keep scaling and decentralizing the Tor
     architecture so it can handle thousands of relays and millions of
     users. The upcoming stable release is a major improvement, but there's
     lots more to be done next in terms of keeping Tor fast and stable.
     </li>
     
     <li>
     User support: With this many users, a lot of people are asking questions
     all the time, offering to help out with things, and so on. We need good
     clean docs, and we need to spend some effort coordinating volunteers.
     </li>
     
     <li>
     Relay support: the Tor network is run by volunteers, but they still need
     attention with prompt bug fixes, explanations when things go wrong,
     reminders to upgrade, and so on. The network itself is a commons, and
     somebody needs to spend some energy making sure the relay operators stay
     happy. We also need to work on <a href="#RelayOS">stability</a> on some
     platforms &mdash; e.g., Tor relays have problems on Win XP currently.
     </li>
     
     <li>
     Usability: Beyond documentation, we also need to work on usability of the
     software itself. This includes installers, clean GUIs, easy configuration
     to interface with other applications, and generally automating all of
     the difficult and confusing steps inside Tor. We've got a start on this
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     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much more work
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     remains &mdash; usability for privacy software has never been easy.
     </li>
     
     <li>
     Incentives: We need to work on ways to encourage people to configure
     their Tors as relays and exit nodes rather than just clients.
     <a href="#EverybodyARelay">We need to make it easy to become a relay,
     and we need to give people incentives to do it.</a>
     </li>
     
     <li>
     Research: The anonymous communications field is full
     of surprises and gotchas. In our copious free time, we
     also help run top anonymity and privacy conferences like <a
     href="http://petsymposium.org/">PETS</a>. We've identified a set of
     critical <a href="<page getinvolved/volunteer>#Research">Tor research questions</a>
     that will help us figure out how to make Tor secure against the variety of
     attacks out there. Of course, there are more research questions waiting
     behind these.
     </li>
     
     </ul>
     
     <p>
     We're continuing to move forward on all of these, but at this rate
     <a href="#WhySlow">the Tor network is growing faster than the developers
     can keep up</a>.
     Now would be an excellent time to add a few more developers to the effort
     so we can continue to grow the network.
     </p>
     
     <p>
     We are also excited about tackling related problems, such as
     censorship-resistance.
     </p>
     
     <p>
     We are proud to have <a href="<page about/sponsors>">sponsorship and support</a>
     from the Omidyar Network, the International Broadcasting Bureau, Bell
     Security Solutions, the Electronic Frontier Foundation, several government
     agencies and research groups, and hundreds of private contributors.
     </p>
     
     <p>
     However, this support is not enough to keep Tor abreast of changes in the
     Internet privacy landscape. Please <a href="<page donate/donate>">donate</a>
     to the project, or <a href="<page about/contact>">contact</a> our executive
     director for information on making grants or major donations.
     </p>
     
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     <a id="HowUninstallTor"></a>
     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
     
     <p>
     This depends entirely on how you installed it and which operating system you
     have. If you installed a package, then hopefully your package has a way to
     uninstall itself. The Windows packages include uninstallers. The proper way to
     completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any
     version of Windows is as follows:
     </p>
     
     <ol>
     <li>In your taskbar, right click on Vidalia (the green onion or the black head)
     and choose exit.</li>
     <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
     Process List. If it's running, right click and choose End Process.</li>
     <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
     This will remove the Vidalia bundle, which includes Tor and Polipo.</li>
     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
     Click the Uninstall button.</li>
     </ol>
     
     <p>
     If you do not follow these steps (for example by trying to uninstall
     Vidalia, Tor, and Polipo while they are still running), you will need to
     reboot and manually remove the directory "Program Files\Vidalia Bundle".
     </p>
     
     <p>
     For Mac OS X, follow the <a
     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
     </p>
     
     <p>
     If you installed by source, I'm afraid there is no easy uninstall method. But
     on the bright side, by default it only installs into /usr/local/ and it should
     be pretty easy to notice things there.
     </p>
     
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     <a id="PGPSigs"></a>
     <h3><a class="anchor" href="#PGPSigs">What are these "sig" files on the
     download page?</a></h3>
     
     <p>
     These are PGP signatures, so you can verify that the file you've downloaded is
     exactly the one that we intended you to get.
     </p>
     
     <p>
     Please read the <a
     href="<page docs/verifying-signatures>">verifying signatures</a> page for details.
     </p>
     
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     <a id="CompileTorWindows"></a>
     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
     Windows?</a></h3>
     
     <p>
     Try following the steps at <a href="<gitblob>doc/tor-win32-mingw-creation.txt">
     tor-win32-mingw-creation.txt</a>.
     </p>
     
     <p>
     (Note that you don't need to compile Tor yourself in order to use
     it. Most people just use the packages available on the <a href="<page
     download/download>">download page</a>.)
     </p>
     
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     <hr>
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     <a id="VirusFalsePositives"></a>
     <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
     executable appear to have a virus or spyware?</a></h3>
     
     <p>
     Sometimes, overzealous Windows virus and spyware detectors trigger on some
     parts of the Tor Windows binary. Our best guess is that these are false
     positives &mdash; after all, the anti-virus and anti-spyware business is just a
     guessing game anyway. You should contact your vendor and explain that you have
     a program that seems to be triggering false positives. Or pick a better vendor.
     </p>
     
     <p>
     In the meantime, we encourage you to not just take our word for
     it. Our job is to provide the source; if you're concerned, please do <a
     href="#CompileTorWindows">recompile it yourself</a>.
     </p>
     
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     <hr>
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     <a id="LiveCD"></a>
     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
     includes Tor?</a></h3>
     
     <p>
     There isn't any official LiveCD at this point. We're still trying to find good
     solutions and trying to understand the security and anonymity implications of
     the various options. In the mean time, feel free to check out the list below
     and use your best judgement:
     </p>
     
     <p>
     LiveCDs:
     </p>
     
     <ol>
     <li><a href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
     System</a> is a Live System aimed at preserving your privacy and
     anonymity:
     <ul>
     <li> All outgoing connections to the Internet are forced to go through
     the Tor network.</li>
     <li> No trace is left on local storage devices unless explicitely asked.</li>
     <li> It includes Firefox, Tor, Torbutton, Vidalia graphical Tor
     controller, Pidgin Instant Messaging client, and lots of other
     software.</li>
     <li> It's based upon Debian gnu/linux and comes with the GNOME desktop
     environment.</li>
     </ul>
     <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
     is Knoppix-based with an emphasis on user-friendliness. You can work
     anonymously or non-anonymously while TorK tries to keep you informed of the
     consequences of your activity. The TorK LiveCD is experimental, so the aim is
     to provide regular releases through 2007 and beyond.</li>
     <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
     debian based live-system including tor, firefox and torbutton which can save
     bookmarks and other settings or data on an encrypted usb-key</li>
     </li>
     </ol>
     
     <p>
     Windows bundles:
     </p>
     
     <ol>
     <li><a href="<page projects/torbrowser>">Tor Browser Bundle</a>
     for Windows comes with a pre-configured web browser and is self contained
     so you can run it from a USB stick.</li>
     <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
     to JanusVM. It needs testing from you!</li>
     <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
     running in VMWare that sits between your Windows computer and the Internet,
     making sure that your Internet traffic is scrubbed and anonymized.</li>
     <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
     previously known as Torpark, is a Firefox+Tor package for Win32 that can
     installed on a USB key. It needs a host Win32 operating system.</li>
     </ol>
     
     <p>
     Not currently maintained as far as we know:
     </p>
     
     <ol>
     <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
     and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
     download</a>.</li>
     <li>ELE is a Linux LiveCD which is focused on privacy related
     software. It includes Tor and you can download it at
     <a
     href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
     <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
     Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
     non-Tor traffic from accidentally leaving your computer. More information at
     <a
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     href="<wiki>VirtualPrivacyMachine"><wiki>VirtualPrivacyMachine</a>.</li>
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     <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
     than Linux for maximum security. It was designed to be anonymous and secure
     from the ground up, and thus has some features and limitations not found in
     other LiveCDs (Tor related or otherwise). You can obtain more information and
     download Anonym.OS from <a href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
     <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
     recent KNOPPIX release. It comes preconfigured with Privoxy, Tor and Polipo. You can
     get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
     Website</a>.</li>
     </ol>
     
     <p>
     Please contact us if you know any others.
     </p>
     
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     <hr>
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     <a id="ChooseEntryExit"></a>
     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>
     
     <p>
     Yes. You can set preferred entry and exit nodes as well as 
     inform Tor which nodes you do not want to use. 
     The following options can be added to your config file "torrc" 
     or specified on the command line:
     </p>
     <dl>
       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
         <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
         </dd>
       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>
         <dd>A list of preferred nodes to use for the last hop in the circuit, if possible. 
         </dd>
       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>
         <dd>A list of nodes to never use when building a circuit. 
         </dd>
       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>
         <dd>A list of nodes to never use when picking an exit. 
             Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list. 
         </dd>
     </dl>
     <p>
     <em>We recommend you do not use these</em> 
     &mdash; they are intended for testing and may disappear in future versions. 
     You get the best security that Tor can provide when you leave the route selection to Tor; 
     overriding the entry / exit nodes can mess up your anonymity in ways we don't understand.
     </p>
     <p>
     The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are treated as a request, 
     meaning if the nodes are down or seem slow, Tor will still avoid them. 
     You can make the option mandatory by setting 
     <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt> 
     &mdash; but if you do, your Tor connections will stop working 
     if all of the nodes you have specified become unreachable. 
     See the <a href="https://www.torproject.org/documentation.html.en#NeatLinks">Tor status pages</a> 
     for some nodes you might pick.
     </p>
     <p>
     Instead of <tt>$fingerprint</tt> you can also specify 
     a 2 letter ISO3166 country code in curly braces 
     (for example {de}), 
     or an ip address pattern (for example 255.254.0.0/8), 
     or a node nickname. 
     Make sure there are no spaces between the commas and the list items. 
     </p>
     <p>
     If you want to access a service directly through Tor's SOCKS interface 
     (eg. using ssh via connect.c), another option is to 
     set up an internal mapping in your configuration file using <tt>MapAddress</tt>. 
     See the manual page for details.
     </p>
     
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     <hr>
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     <a id="RelayFlexible"></a>
     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
     need to be?</a></h3>
     
     <p>
     We aim to make setting up a Tor relay easy and convenient:
     </p>
     
     <ul>
     <li>Tor has built-in support for <a
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     href="<wikifaq>#LimitBandwidth">
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     rate limiting</a>. Further, if you have a fast
     link but want to limit the number of bytes per
     day (or week or month) that you donate, check out the <a
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     href="<wikifaq>#Hibernation">hibernation
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     feature</a>.
     </li>
     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
     specifies what sort of outbound connections are allowed or refused from
     that relay. If you are uncomfortable allowing people to exit from your
     relay, you can set it up to only allow connections to other Tor relays.
     </li>
     <li>It's fine if the relay goes offline sometimes. The directories
     notice this quickly and stop advertising the relay. Just try to make
     sure it's not too often, since connections using the relay when it
     disconnects will break.
     </li>
     <li>We can handle relays with dynamic IPs just fine &mdash; simply
     leave the Address config option blank, and Tor will try to guess.
     </li>
     <li>If your relay is behind a NAT and it doesn't know its public
     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port
     forwarding. Forwarding TCP connections is system dependent but 
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     <a href="<wikifaq>#ServerForFirewalledClients">this FAQ entry</a> 
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     offers some examples on how to do this.
     </li>
     <li>Your relay will passively estimate and advertise its recent
     bandwidth capacity, so high-bandwidth relays will attract more users than
     low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
     </li>
     </ul>
     
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     <hr>
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     <a id="RunARelayBut"></a>
     <a id="ExitPolicies"></a>
     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't
     want to deal with abuse issues.</a></h3>
     
     <p>
     Great. That's exactly why we implemented exit policies.
     </p>
     
     <p>
     Each Tor relay has an exit policy that specifies what sort of
     outbound connections are allowed or refused from that relay. The exit
     policies are propagated to Tor clients via the directory, so clients
     will automatically avoid picking exit relays that would refuse to
     exit to their intended destination. This way each relay can decide
     the services, hosts, and networks he wants to allow connections to,
     based on abuse potential and his own situation. Read the FAQ entry on 
     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might encounter</a> 
     if you use the default exit policy, and then read Mike Perry's 
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     <a href="<blog>tips-running-exit-node-minimal-harassment">tips
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     for running an exit node with minimal harassment</a>.
     </p>
     
     <p>
     The default exit policy allows access to many popular services (e.g. web browsing), but 
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     <a href="<wikifaq>#DefaultPorts">restricts</a>
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     some due to abuse potential (e.g. mail) and some since
     the Tor network can't handle the load (e.g. default
     file-sharing ports). You can change your exit policy
     using Vidalia's "Sharing" tab, or by manually editing your 
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     <a href="<wikifaq>#torrc">torrc</a>
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     file. If you want to avoid most if not all abuse potential, set it to
     "reject *:*" (or un-check all the boxes in Vidalia). This setting means
     that your relay will be used for relaying traffic inside the Tor network,
     but not for connections to external websites or other services.
     </p>
     
     <p>
     If you do allow any exit connections, make sure name resolution works
     (that is, your computer can resolve Internet addresses correctly).
     If there are any resources that your computer can't reach (for example,
     you are behind a restrictive firewall or content filter), please
     explicitly reject them in your exit policy &mdash; otherwise Tor users
     will be impacted too.
     </p>
     
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     <hr>
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     <a id="RelayOrBridge"></a>
     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay
     or bridge relay?</a></h3>
     
     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for short)
     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
     in the main Tor directory. That means
     that even an ISP or government trying to filter connections to the Tor
     network probably won't be able to block all the bridges.
     </p>
     
     <p>Being a normal relay vs being a bridge relay is almost the same
     configuration: it's just a matter of whether your relay is listed
     publically or not.
     </p>
     
     <p>Right now, there are roughly zero places in the world that filter
     connections to the Tor network. So getting a lot of bridges running
     right now is mostly a backup measure, a) in case the Tor network does
     get blocked somewhere, and b) for people who want an extra layer of
     security because they're worried somebody will recognize that it's a
     public Tor relay IP address they're contacting.
     </p>
     
     <p>So should you run a normal relay or bridge relay? If you have
     lots of bandwidth, you should definitely run a normal relay &mdash;
     bridge relays see very little use these days. If you're willing to 
     <a href="#ExitPolicies">be an exit</a>, you should definitely run a normal
     relay, since we need more exits. If you can't be an exit and only have
     a little bit of bandwidth, then flip a coin. Thanks for volunteering!
     </p>
     
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     <hr>
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     <a id="RelayMemory"></a>
     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so
     much memory?</a></h3>
     
     <p>If your Tor relay is using more memory than you'd like, here are some
     tips for reducing its footprint:
     </p>
     
     <ol>
     <li>If you're on Linux, you may be encountering memory fragmentation
     bugs in glibc's malloc implementation. That is, when Tor releases memory
     back to the system, the pieces of memory are fragmented so they're hard
     to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
     which doesn't have as many fragmentation bugs (but the tradeoff is higher
     CPU load). You can tell Tor to use this malloc implementation instead:
     <tt>./configure --enable-openbsd-malloc</tt></li>
     
     <li>If you're running a fast relay, meaning you have many TLS connections
     open, you are probably losing a lot of memory to OpenSSL's internal
     buffers (38KB+ per socket). We've patched OpenSSL to <a
     href="http://archives.seul.org/or/dev/Jun-2008/msg00001.html">release
     unused buffer memory more aggressively</a>. If you update to OpenSSL
     1.0.0-beta5, Tor's build process will automatically recognize and use
     this feature.</li>
     
     <li>If you're running on Solaris, OpenBSD, NetBSD, or
     old FreeBSD, Tor is probably forking separate processes
     rather than using threads. Consider switching to a <a
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     href="<wikifaq>#RelayOS">better
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     operating system</a>.</li>
     
     <li>If you still can't handle the memory load, consider reducing the
     amount of bandwidth your relay advertises. Advertising less bandwidth
     means you will attract fewer users, so your relay shouldn't grow
     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
     page.</li>
     
     </ol>
     
     <p>
     All of this said, fast Tor relays do use a lot of ram. It is not unusual
     for a fast exit relay to use 500-1000 MB of memory.
     </p>
     
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     <hr>
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     <a id="WhyNotNamed"></a>
     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not named?</a></h3>
     
     <p>
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     We currently use these metrics to determine if your relay should be named:<br>
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     </p>
     <ul>
     <li>The name is not currently mapped to a different key. Existing mappings
     are removed after 6 months of inactivity from a relay.</li>
     <li>The relay must have been around for at least two weeks.</li>
     <li>No other router may have wanted the same name in the past month.</li>
     </ul>
     
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     <hr>
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     <a id="KeyManagement"></a>
     <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
     Tor uses.</a></h3>
     
     <p>
     Tor uses a variety of different keys, with three goals in mind: 1)
     encryption to ensure privacy of data within the Tor network, 2)
     authentication so clients know they're
     talking to the relays they meant to talk to, and 3) signatures to make
     sure all clients know the same set of relays.
     </p>
     
     <p>
     <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
     so observers can't look inside to see which circuit a given cell is
     intended for. Further, the Tor client establishes an ephemeral encryption
     key with each relay in the circuit, so only the exit relay can read
     the cells. Both sides discard the circuit key when the circuit ends,
     so logging traffic and then breaking into the relay to discover the key
     won't work.
     </p>
     
     <p>
     <b>Authentication</b>:
     Every Tor relay has a public decryption key called the "onion key".
     When the Tor client establishes circuits, at each step it <a
     href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands
     that the Tor relay prove knowledge of its onion key</a>. That way
     the first node in the path can't just spoof the rest of the path.
     Each relay rotates its onion key once a week.
     </p>
     
     <p>
     <b>Coordination</b>:
     How do clients know what the relays are, and how do they know that they
     have the right keys for them? Each relay has a long-term public signing
     key called the "identity key". Each directory authority additionally has a
     "directory signing key". The directory authorities <a
     href="<gitblob>doc/spec/dir-spec.txt">provide a signed list</a>
     of all the known relays, and in that list are a set of certificates from
     each relay (self-signed by their identity key) specifying their keys,
     locations, exit policies, and so on. So unless the adversary can control
     a threshold of the directory authorities, he can't trick the Tor client
     into using other Tor relays.
     </p>
     
     <p>
     How do clients know what the directory authorities are? The Tor software
     comes with a built-in list of location and public key for each directory
     authority. So the only way to trick users into using a fake Tor network
     is to give them a specially modified version of the software.
     </p>
     
     <p>
     How do users know they've got the right software? When we distribute
     the source code or a package, we digitally sign it with <a
     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
     href="<page docs/verifying-signatures>">instructions
     on how to check Tor's signatures</a>.
     </p>
     
     <p>
     In order to be certain that it's really signed by us, you need to have
     met us in person and gotten a copy of our GPG key fingerprint, or you
     need to know somebody who has. If you're concerned about an attack on
     this level, we recommend you get involved with the security community
     and start meeting people.
     </p>
     
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     <hr>
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     <a id="EverybodyARelay"></a>
     <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
     user be a relay.</a></h3>
     
     <p>
     Requiring every Tor user to be a relay would help with scaling the
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     network to handle all our users, and <a href="<wikifaq>#RelayAnonymity">running a Tor
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     relay may help your anonymity</a>. However, many Tor users cannot be good
     relays &mdash; for example, some Tor clients operate from behind restrictive
     firewalls, connect via modem, or otherwise aren't in a position where they
     can relay traffic. Providing service to these clients is a critical
     part of providing effective anonymity for everyone, since many Tor users
     are subject to these or similar constraints and including these clients
     increases the size of the anonymity set.
     </p>
     
     <p>
     That said, we do want to encourage Tor users to run relays, so what we
     really want to do is simplify the process of setting up and maintaining
     a relay. We've made a lot of progress with easy configuration in the past
     few years: Vidalia has an easy relay configuration interface, and supports
     uPnP too. Tor is good at automatically detecting whether it's reachable and
     how much bandwidth it can offer.
     </p>
     
     <p>
     There are five steps we need to address before we can do this though:
     </p>
     
     <p>
     First, we need to make Tor stable as a relay on all common
     operating systems. The main remaining platform is Windows,
     and we plan to finally address that in 2009. See Section 4.1 of <a
     href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
     development roadmap</a>.
     </p>
     
     <p>
     Second, we still need to get better at automatically estimating
     the right amount of bandwidth to allow. See item #7 on the
     <a href="<page getinvolved/volunteer>#Research">research section of the
     volunteer page</a>: "Tor doesn't work very well when relays
     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a
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     href="<wikifaq>#TransportIPnotTCP">switching
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     to UDP transport</a> is the simplest answer here &mdash; which alas is
     not a very simple answer at all.
     </p>
     
     <p>
     Third, we need to work on scalability, both of the network (how to
     stop requiring that all Tor relays be able to connect to all Tor
     relays) and of the directory (how to stop requiring that all Tor
     users know about all Tor relays). Changes like this can have large
     impact on potential and actual anonymity. See Section 5 of the <a
     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
     for details. Again, UDP transport would help here.
     </p>
     
     <p>
     Fourth, we need to better understand the risks from
     letting the attacker send traffic through your relay while
     you're also initiating your own anonymized traffic. <a
     href="http://freehaven.net/anonbib/#back01">Three</a> <a
     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
     describe ways to identify the relays in a circuit by running traffic
     through candidate relays and looking for dips in the traffic while the
     circuit is active. These clogging attacks are not that scary in the Tor
     context so long as relays are never clients too. But if we're trying to
     encourage more clients to turn on relay functionality too (whether as
     <a href="<page docs/bridges>">bridge relays</a> or as normal relays), then
     we need to understand this threat better and learn how to mitigate it.
     </p>
     
     <p>
     Fifth, we might need some sort of incentive scheme to encourage people
     to relay traffic for others, and/or to become exit nodes. Here are our
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     <a href="<blog>two-incentive-designs-tor">current
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     thoughts on Tor incentives</a>.
     </p>
     
     <p>
     Please help on all of these!
     </p>
     
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     <hr>
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     <a id="Criminals"></a>
     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
     things?</a></h3>
     
     <p>
     For the answer to this question and others, please see our <a
     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
     </p>
     
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     <hr>
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     <a id="RespondISP"></a>
     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
     exit relay?</a></h3>
     
     <p>
     A collection of templates for successfully responding to ISPs is <a
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     href="<wiki>TheOnionRouter/TorAbuseTemplates">collected
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     here</a>.
     </p>
     
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     <hr>
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