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4) #include "head.wmi" TITLE="Tor FAQ"
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9) 

10) # Translators: you probably don't want to translate this file yet,
11) # since I'm hoping it will keep changing for a while. Thanks! -RD
12) 

13) <h2>Tor FAQ</h2>
14) <hr />

15) 

16) <p>General questions:</p>

17) <ul>

18) <li><a href="#WhatIsTor">What is Tor?</a></li>
19) <li><a href="#CompatibleApplications">What programs can I use with
20) Tor?</a></li>
21) <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
22) <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
23) <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
24) CD?</a></li>
25) <li><a href="#SupportMail">How can I get an answer to my
26) Tor support mail?</a></li>
27) <li><a href="#WhySlow">Why is Tor so slow?</a></li>
28) <li><a href="#Funding">What would The Tor Project do with more
29) funding?</a></li>

30) </ul>
31) 

32) <p>Compilation and Installation:</p>

33) <ul>
34) <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>

35) <li><a href="#PGPSigs">What are these "sig" files on the download
36) page?</a></li>

37) <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>

38) <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
39) have a virus or spyware?</a></li>

40) <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</li>
41) </ul>

42) 
43) <p>Running Tor:</p>
44) 
45) <p>Running a Tor client:</p>
46) 
47) <p>Running a Tor relay:</p>
48) 
49) <p>Running a Tor hidden service:</p>
50) 

51) <p>Anonymity and Security:</p>
52) <ul>

53) <li><a href="#KeyManagement">Tell me about all the keys Tor uses.</a></li>

54) </ul>
55) 

56) <p>Alternate designs that we don't do (yet):</p>
57) <ul>
58) <li><a href="#EverybodyARelay">You should make every Tor user be a
59) relay.</a></li>
60) </ul>
61) 

62) <p>Abuse</p>
63) <ul>
64) <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
65) <li><a href="#RespondISP">How do I respond to my ISP about my exit
66) relay?</a></li>
67) </ul>
68) 

69) <p>For other questions not yet on this version of the FAQ, see the <a
70) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ">wiki
71) FAQ</a> for now.</p>
72) 

73) <hr />
74) 
75) <a id="General"></a>
76) 

77) <a id="WhatIsTor"></a>
78) <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
79) 
80) <p>
81) The name "Tor" can refer to several different components.
82) </p>
83) 
84) <p>
85) The Tor software is a program you can run on your computer that helps keep
86) you safe on the Internet. Tor protects you by bouncing your communications
87) around a distributed network of relays run by volunteers all around
88) the world: it prevents somebody watching your Internet connection from
89) learning what sites you visit, and it prevents the sites you visit
90) from learning your physical location. This set of volunteer relays is
91) called the Tor network. You can read more about how Tor works on the <a
92) href="<page overview>">overview page</a>.
93) </p>
94) 
95) <p>
96) The Tor Project is a non-profit (charity) organization that maintains

97) and develops the Tor software.

98) </p>
99) 

100) <a id="CompatibleApplications"></a>

101) <h3><a class="anchor" href="#CompatibleApplications">What programs can
102) I use with Tor?</a></h3>

103) 
104) <p>
105) There are two pieces to "Torifying" a program: connection-level anonymity
106) and application-level anonymity. Connection-level anonymity focuses on

107) making sure the application's Internet connections get sent through Tor.
108) This step is normally done by configuring

109) the program to use your Tor client as a "socks" proxy, but there are
110) other ways to do it too. For application-level anonymity, you need to
111) make sure that the information the application sends out doesn't hurt
112) your privacy. (Even if the connections are being routed through Tor, you
113) still don't want to include sensitive information like your name.) This
114) second step needs to be done on a program-by-program basis, which is
115) why we don't yet recommend very many programs for safe use with Tor.

116) </p>
117) 
118) <p>

119) Most of our work so far has focused on the Firefox web browser. The
120) bundles on the <a href="<page download>">download page</a> automatically
121) install the <a href="<page torbutton/index>">Torbutton Firefox
122) extension</a> if you have Firefox installed. As of version 1.2.0,
123) Torbutton now takes care of a lot of the connection-level and
124) application-level worries.

125) </p>
126) 
127) <p>

128) There are plenty of other programs you can use with Tor,
129) but we haven't researched the application-level anonymity
130) issues on them well enough to be able to recommend a safe
131) configuration. Our wiki has a list of instructions for <a

132) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorifyHOWTO">Torifying

133) specific applications</a>. There's also a <a
134) href="https://wiki.torproject.org/noreply/TheOnionRouter/SupportPrograms">list
135) of applications that help you direct your traffic through Tor</a>.
136) Please add to these lists and help us keep them accurate!

137) </p>
138) 
139) <a id="WhyCalledTor"></a>
140) <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
141) 
142) <p>

143) Because Tor is the onion routing network. When we were starting the
144) new next-generation design and implementation of onion routing in
145) 2001-2002, we would tell people we were working on onion routing,
146) and they would say "Neat. Which one?" Even if onion routing has
147) become a standard household term, Tor was born out of the actual <a
148) href="http://www.onion-router.net/">onion routing project</a> run by
149) the Naval Research Lab.

150) </p>
151) 
152) <p>

153) (It's also got a fine translation from German and Turkish.)

154) </p>
155) 
156) <p>

157) Note: even though it originally came from an acronym, Tor is not spelled

158) "TOR". Only the first letter is capitalized. In fact, we can usually
159) spot people who haven't read any of our website (and have instead learned
160) everything they know about Tor from news articles) by the fact that they
161) spell it wrong.

162) </p>
163) 
164) <a id="Backdoor"></a>
165) <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
166) 
167) <p>

168) There is absolutely no backdoor in Tor. Nobody has asked us to put one

169) in, and we know some smart lawyers who say that it's unlikely that anybody

170) will try to make us add one in our jurisdiction (U.S.). If they do

171) ask us, we will fight them, and (the lawyers say) probably win.
172) </p>
173) 
174) <p>
175) We think that putting a backdoor in Tor would be tremendously
176) irresponsible to our users, and a bad precedent for security software

177) in general. If we ever put a deliberate backdoor in our security
178) software, it would ruin our professional reputations. Nobody would

179) trust our software ever again — for excellent reason!
180) </p>
181) 
182) <p>
183) But that said, there are still plenty of subtle attacks

184) people might try. Somebody might impersonate us, or break into our
185) computers, or something like that. Tor is open source, and you should

186) always check the source (or at least the diffs since the last release)

187) for suspicious things. If we (or the distributors) don't give you

188) source, that's a sure sign something funny might be going on. You

189) should also check the <a
190) href="https://wiki.torproject.org/noreply/TheOnionRouter/VerifyingSignatures">PGP
191) signatures</a> on the releases, to make sure nobody messed with the
192) distribution sites.

193) </p>
194) 
195) <p>
196) Also, there might be accidental bugs in Tor that could affect your

197) anonymity. We periodically find and fix anonymity-related bugs, so make
198) sure you keep your Tor versions up-to-date.

199) </p>
200) 
201) <a id="DistributingTor"></a>
202) <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on

203) my magazine's CD?</a></h3>

204) 
205) <p>
206) Yes.
207) </p>
208) 
209) <p>

210) The Tor software is <a href="https://www.fsf.org/">free software</a>. This

211) means we give you the rights to redistribute the Tor software, either
212) modified or unmodified, either for a fee or gratis. You don't have to
213) ask us for specific permission.
214) </p>
215) 
216) <p>
217) However, if you want to redistribute the Tor software you must follow our

218) <a href="<svnsandbox>license">LICENSE</a>.

219) Essentially this means that you need to include our LICENSE file along
220) with whatever part of the Tor software you're distributing.
221) </p>
222) 
223) <p>
224) Most people who ask us this question don't want to distribute just the
225) Tor software, though. They want to distribute the Tor bundles, which
226) typically include <a href="http://www.privoxy.org/">Privoxy</a>
227) and <a href="http://www.vidalia-project.net/">Vidalia</a>.
228) You will need to follow the licenses for those programs
229) as well. Both of them are distributed under the <a

230) href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General

231) Public License</a>. The simplest way to obey their licenses is to
232) include the source code for these programs everywhere you include
233) the bundles themselves. Look for "source" packages on the <a
234) href="http://www.vidalia-project.net/download.php">Vidalia
235) download page</a> and the <a
236) href="http://sourceforge.net/project/showfiles.php?group_id=11118">Privoxy
237) download page</a>.
238) </p>
239) 
240) <p>

241) Also, you should make sure not to confuse your readers about what Tor is,

242) who makes it, and what properties it provides (and doesn't provide). See
243) our <a href="<page trademark-faq>">trademark FAQ</a> for details.
244) </p>
245) 
246) <p>
247) Lastly, you should realize that we release new versions of the
248) Tor software frequently, and sometimes we make backward incompatible
249) changes. So if you distribute a particular version of the Tor software, it
250) may not be supported &mdash; or even work &mdash; six months later. This
251) is a fact of life for all security software under heavy development.
252) </p>
253) 
254) <a id="SupportMail"></a>
255) <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
256) Tor support mail?</a></h3>
257) 
258) <p>
259) Many people send the Tor developers mail privately, or send mail to

260) our internal <a href="<page contact>">lists</a>, with questions about their

261) specific setup — they can't get their firewall working right,

262) they can't configure Privoxy correctly, or so on. Sometimes our
263) volunteers can answer these mails, but typically they need to spend
264) most of their time on development tasks that will benefit more people.
265) This is especially true if your question is already covered in the <a
266) href="<page documentation>">documentation</a> or on this FAQ. We don't
267) hate you; we're just busy.
268) </p>
269) 
270) <p>
271) So if we don't answer your mail, first check the <a href="<page
272) documentation>">documentation</a> page, along with this FAQ,
273) to make sure your question isn't already answered.  Then read <a
274) href="http://www.catb.org/~esr/faqs/smart-questions.html">"How to ask
275) questions the smart way"</a>. If this doesn't help you, note that we
276) have <a href="<page documentation>#Support">an IRC channel</a> where you
277) can ask your questions (but if they are still open-ended, ill-formed,
278) or not about Tor, you likely won't get much help there either). Lastly,
279) people on the <a href="<page documentation>#MailingLists">or-talk
280) mailing list</a> may be able to provide some hints for you, if
281) others have experienced your problems too. Be sure to look over <a
282) href="http://archives.seul.org/or/talk/">the archives</a> first.
283) </p>
284) 
285) <p>
286) Another strategy is to <a href="<page docs/tor-doc-relay>">run a Tor
287) relay for a while</a>, and/or <a href="<page donate>">donate money</a>
288) <a href="<page volunteer>">or time</a> to the effort. We're more likely
289) to pay attention to people who have demonstrated interest and commitment
290) to giving back to the Tor community.
291) </p>
292) 
293) <p>

294) If you find your answer, please stick around on the IRC channel or the

295) mailing list and answer questions from others.
296) </p>
297) 
298) <a id="WhySlow"></a>
299) <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
300) 
301) <p>
302) There are many reasons why the Tor network is currently slow.
303) </p>
304) 
305) <p>
306) Before we answer, though, you should realize that Tor is never going to
307) be blazing fast. Your traffic is bouncing through volunteers' computers
308) in various parts of the world, and some bottlenecks and network latency
309) will always be present. You shouldn't expect to see university-style
310) bandwidth through Tor.
311) </p>
312) 
313) <p>
314) But that doesn't mean that it can't be improved. The current Tor network
315) is quite small compared to the number of people trying to use it, and
316) many of these users don't understand or care that Tor can't currently
317) handle file-sharing traffic load.
318) </p>
319) 
320) <p>
321) What can you do to help?
322) </p>
323) 
324) <ul>
325) 
326) <li>
327) <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
328) for others</a>. Help make the Tor network large enough that we can handle
329) all the users who want privacy and security on the Internet.
330) </li>
331) 
332) <li>
333) <a href="<page gui/index>">Help us make Tor more usable</a>. We
334) especially need people to help make it easier to configure your Tor
335) as a relay. Also, we need help with clear simple documentation to
336) walk people through setting it up.
337) </li>
338) 
339) <li>
340) There are some bottlenecks in the current Tor network. Help us design
341) experiments to track down and demonstrate where the problems are, and
342) then we can focus better on fixing them.
343) </li>
344) 
345) <li>
346) There are some steps that individuals
347) can take to improve their Tor performance. <a
348) href="https://wiki.torproject.org/noreply/TheOnionRouter/FireFoxTorPerf">You
349) can configure your Firefox to handle Tor better</a>, <a
350) href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
351) Polipo with Tor</a>, or you can try <a href="<page download>">upgrading
352) to the latest version of Tor</a>.  If this works well, please help by
353) documenting what you did, and letting us know about it.
354) </li>
355) 
356) <li>
357) Tor needs some architectural changes too. One important change is to

358) start providing <a

359) href="#EverybodyARelay">better

360) service to people who relay traffic</a>. We're working on this, and
361) we'll finish faster if we get to spend more time on it.

362) </li>
363) 
364) <li>
365) Help do other things so we can do the hard stuff. Please take a moment
366) to figure out what your skills and interests are, and then <a href="<page
367) volunteer>">look at our volunteer page</a>.
368) </li>
369) 
370) <li>
371) Help find sponsors for Tor. Do you work at a company or government agency
372) that uses Tor or has a use for Internet privacy, e.g. to browse the
373) competition's websites discreetly, or to connect back to the home servers
374) when on the road without revealing affiliations? If your organization has
375) an interest in keeping the Tor network working, please contact them about
376) supporting Tor. Without sponsors, Tor is going to become even slower.
377) </li>
378) 
379) <li>
380) If you can't help out with any of the above, you can still help out
381) individually by <a href="<page donate>">donating a bit of money to the
382) cause</a>. It adds up!
383) </li>
384) 
385) </ul>
386) 
387) <a id="Funding"></a>

388) <h3><a class="anchor" href="#Funding">What would The Tor Project do with

389) more funding?</a></h3>
390) 
391) <p>
392) We have about 1500 relays right now, pushing over 150 MB/s average
393) traffic. We have several hundred thousand active users. But the Tor
394) network is not yet self-sustaining.
395) </p>
396) 
397) <p>
398) There are six main development/maintenance pushes that need attention:
399) </p>
400) 
401) <ul>
402) 
403) <li>
404) Scalability: We need to keep scaling and decentralizing the Tor
405) architecture so it can handle thousands of relays and millions of
406) users. The upcoming stable release is a major improvement, but there's
407) lots more to be done next in terms of keeping Tor fast and stable.
408) </li>
409) 
410) <li>
411) User support: With this many users, a lot of people are asking questions
412) all the time, offering to help out with things, and so on. We need good
413) clean docs, and we need to spend some effort coordinating volunteers.
414) </li>
415) 
416) <li>
417) Relay support: the Tor network is run by volunteers, but they still need
418) attention with prompt bug fixes, explanations when things go wrong,
419) reminders to upgrade, and so on. The network itself is a commons, and
420) somebody needs to spend some energy making sure the relay operators stay
421) happy. We also need to work on <a href="#RelayOS">stability</a> on some
422) platforms &mdash; e.g., Tor relays have problems on Win XP currently.
423) </li>
424) 
425) <li>
426) Usability: Beyond documentation, we also need to work on usability of the
427) software itself. This includes installers, clean GUIs, easy configuration
428) to interface with other applications, and generally automating all of
429) the difficult and confusing steps inside Tor. We've got a start on this
430) with the <a href="<page gui/index>">GUI Contest</a>, but much more work
431) remains &mdash; usability for privacy software has never been easy.
432) </li>
433) 
434) <li>
435) Incentives: We need to work on ways to encourage people to configure
436) their Tors as relays and exit nodes rather than just clients.
437) <a href="#EverybodyARelay">We need to make it easy to become a relay,
438) and we need to give people incentives to do it.</a>
439) </li>
440) 
441) <li>
442) Research: The anonymous communications field is full
443) of surprises and gotchas. In our copious free time, we
444) also help run top anonymity and privacy conferences like <a
445) href="http://petsymposium.org/">PETS</a>. We've identified a set of
446) critical <a href="<page volunteer>#Research">Tor research questions</a>
447) that will help us figure out how to make Tor secure against the variety of
448) attacks out there. Of course, there are more research questions waiting
449) behind these.
450) </li>
451) 
452) </ul>
453) 
454) <p>
455) We're continuing to move forward on all of these, but at this rate
456) <a href="#WhySlow">the Tor network is growing faster than the developers
457) can keep up</a>.
458) Now would be an excellent time to add a few more developers to the effort
459) so we can continue to grow the network.
460) </p>
461) 
462) <p>
463) We are also excited about tackling related problems, such as
464) censorship-resistance.
465) </p>
466) 
467) <p>
468) We are proud to have <a href="<page sponsors>">sponsorship and support</a>
469) from the Omidyar Network, the International Broadcasting Bureau, Bell
470) Security Solutions, the Electronic Frontier Foundation, several government
471) agencies and research groups, and hundreds of private contributors.
472) </p>
473) 
474) <p>
475) However, this support is not enough to keep Tor abreast of changes in the
476) Internet privacy landscape. Please <a href="<page donate>">donate</a>
477) to the project, or <a href="<page contact>">contact</a> our executive
478) director for information on making grants or major donations.
479) </p>
480) 
481) <hr />
482) 

483) <a id="HowUninstallTor"></a>
484) <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
485) 
486) <p>
487) This depends entirely on how you installed it and which operating system you
488) have. If you installed a package, then hopefully your package has a way to

489) uninstall itself. The Windows packages include uninstallers. The proper way to

490) completely remove Tor, Vidalia, Torbutton for Firefox, and Privoxy on any
491) version of Windows is as follows:
492) </p>
493) 
494) <ol>
495) <li>In your taskbar, right click on Privoxy (the blue icon with a white "P")
496) and choose exit.</li>
497) <li>In your taskbar, right click on Vidalia (the green onion or the black head)
498) and choose exit.</li>
499) <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
500) Process List. If it's running, right click and choose End Process.</li>
501) <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
502) This will remove the Vidalia bundle, which includes Tor and Privoxy.</li>
503) <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
504) Click the Uninstall button.</li>

505) </ol>

506) 
507) <p>

508) If you do not follow these steps (for example by trying to uninstall
509) Vidalia, Tor, and Privoxy while they are still running), you will need to
510) reboot and manually remove the directory "Program Files\Vidalia Bundle".

511) </p>
512) 
513) <p>
514) For Mac OS X, follow the <a

515) href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.

516) </p>
517) 
518) <p>
519) If you installed by source, I'm afraid there is no easy uninstall method. But
520) on the bright side, by default it only installs into /usr/local/ and it should
521) be pretty easy to notice things there.
522) </p>
523) 
524) <hr />
525) 

526) <a id="PGPSigs"></a>
527) <h3><a class="anchor" href="#PGPSigs">What are these "sig" files on the
528) download page?</a></h3>

529) 
530) <p>
531) These are PGP signatures, so you can verify that the file you've downloaded is
532) exactly the one that we intended you to get.
533) </p>
534) 
535) <p>
536) Please read the <a
537) href="https://wiki.torproject.org/noreply/TheOnionRouter/VerifyingSignatures">verifying
538) signatures</a> page for details.
539) </p>
540) 
541) <hr />
542) 
543) <a id="CompileTorWindows"></a>
544) <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
545) Windows?</a></h3>
546) 
547) <p>
548) Try following the steps at <a

549) href="<svnsandbox>doc/tor-win32-mingw-creation.txt"><svnsandbox>doc/tor-win32-mingw-creation.txt</a>.

550) </p>
551) 

552) <p>
553) (Note that you don't need to compile Tor yourself in order to use
554) it. Most people just use the packages available on the <a href="<page
555) download>">download page</a>.)
556) </p>
557) 

558) <hr />
559) 

560) <a id="VirusFalsePositives"></a>
561) <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
562) executable appear to have a virus or spyware?</a></h3>

563) 
564) <p>
565) Sometimes, overzealous Windows virus and spyware detectors trigger on some
566) parts of the Tor Windows binary. Our best guess is that these are false

567) positives — after all, the anti-virus and anti-spyware business is just a

568) guessing game anyway. You should contact your vendor and explain that you have
569) a program that seems to be triggering false positives. Or pick a better vendor.
570) </p>
571) 
572) <p>

573) In the meantime, we encourage you to not just take our word for
574) it. Our job is to provide the source; if you're concerned, please do <a
575) href="#CompileTorWindows">recompile it yourself</a>.

576) </p>
577) 
578) <hr />
579) 
580) <a id="LiveCD"></a>
581) <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
582) includes Tor?</a></h3>
583) 
584) <p>
585) There isn't any official LiveCD at this point. We're still trying to find good
586) solutions and trying to understand the security and anonymity implications of
587) the various options. In the mean time, feel free to check out the list below
588) and use your best judgement:
589) </p>
590) 
591) <p>

592) LiveCDs:

593) </p>
594) 
595) <ol>
596) <li><a href="http://incognito.anonymityanywhere.com/">Incognito LiveCD/USB</a>
597) is a CD you can boot that has several Internet applications (Firefox, IRC,
598) Mail, etc) pre-configured to use Tor. For most computers everything is
599) automatically configured and you're ready to go. You can even copy the CD to a
600) USB drive. Includes TorK.</li>

601) <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
602) is Knoppix-based with an emphasis on user-friendliness. You can work
603) anonymously or non-anonymously while TorK tries to keep you informed of the
604) consequences of your activity. The TorK LiveCD is experimental, so the aim is
605) to provide regular releases through 2007 and beyond.</li>

606) <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
607) debian based live-system including tor, firefox and torbutton which can save
608) bookmarks and other settings or data on an encrypted usb-key</li>

609) </ol>
610) 
611) <p>
612) Windows bundles:
613) </p>
614) 
615) <ol>

616) <li><a href="<page torbrowser/index>">Tor Browser Bundle</a>

617) for Windows comes with a pre-configured web browser and is self contained
618) so you can run it from a USB stick.</li>
619) <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
620) to JanusVM. It needs testing from you!</li>
621) <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
622) running in VMWare that sits between your Windows computer and the Internet,
623) making sure that your Internet traffic is scrubbed and anonymized.</li>
624) <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
625) previously known as Torpark, is a Firefox+Tor package for Win32 that can
626) installed on a USB key. It needs a host Win32 operating system.</li>

627) </ol>
628) 
629) <p>
630) Not currently maintained as far as we know:
631) </p>
632) 
633) <ol>

634) <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
635) and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
636) download</a>.</li>

637) <li>ELE is a Linux LiveCD which is focused on privacy related
638) software. It includes Tor and you can download it at
639) <a
640) href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
641) <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
642) Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
643) non-Tor traffic from accidentally leaving your computer. More information at
644) <a

645) href="https://wiki.torproject.org/noreply/VirtualPrivacyMachine">https://wiki.torproject.org/noreply/VirtualPrivacyMachine</a>.</li>

646) <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
647) than Linux for maximum security. It was designed to be anonymous and secure
648) from the ground up, and thus has some features and limitations not found in
649) other LiveCDs (Tor related or otherwise). You can obtain more information and
650) download Anonym.OS from <a
651) href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
652) <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
653) recent KNOPPIX release. It comes preconfigured with tor and privoxy. You can
654) get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
655) Website</a>.</li>
656) </ol>
657) 

658) <p>
659) Please contact us if you know any others.
660) </p>
661) 

662) <hr />
663) 

664) <a id="KeyManagement"></a>

665) <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
666) Tor uses.</a></h3>

667) 
668) <p>

669) Tor uses a variety of different keys, with three goals in mind: 1)

670) encryption to ensure privacy of data within the Tor network, 2)
671) authentication so clients know they're
672) talking to the relays they meant to talk to, and 3) signatures to make
673) sure all clients know the same set of relays.

674) </p>
675) 
676) <p>
677) <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
678) so observers can't look inside to see which circuit a given cell is
679) intended for. Further, the Tor client establishes an ephemeral encryption
680) key with each relay in the circuit, so only the exit relay can read
681) the cells. Both sides discard the circuit key when the circuit ends,
682) so logging traffic and then breaking into the relay to discover the key
683) won't work.
684) </p>
685) 
686) <p>
687) <b>Authentication</b>:
688) Every Tor relay has a public decryption key called the "onion key".
689) When the Tor client establishes circuits, at each step it <a
690) href="<svnsandbox>doc/design-paper/tor-design.html#subsec:circuits">demands
691) that the Tor relay prove knowledge of its onion key</a>. That way

692) the first node in the path can't just spoof the rest of the path.

693) Each relay rotates its onion key once a week.

694) </p>
695) 
696) <p>

697) <b>Coordination</b>:

698) How do clients know what the relays are, and how do they know that they

699) have the right keys for them? Each relay has a long-term public signing
700) key called the "identity key". Each directory authority additionally has a

701) "directory signing key". The directory authorities <a
702) href="<svnsandbox>doc/spec/dir-spec.txt">provide a signed list</a>

703) of all the known relays, and in that list are a set of certificates from
704) each relay (self-signed by their identity key) specifying their keys,
705) locations, exit policies, and so on. So unless the adversary can control
706) a threshold of the directory authorities, he can't trick the Tor client
707) into using other Tor relays.

708) </p>
709) 
710) <p>

711) How do clients know what the directory authorities are? The Tor software
712) comes with a built-in list of location and public key for each directory
713) authority. So the only way to trick users into using a fake Tor network

714) is to give them a specially modified version of the software.
715) </p>

716) 

717) <p>
718) How do users know they've got the right software? When we distribute
719) the source code or a package, we digitally sign it with <a

720) href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a

721) href="https://wiki.torproject.org/noreply/TheOnionRouter/VerifyingSignatures">instructions
722) on how to check Tor's signatures</a>.
723) </p>

724) 

725) <p>

726) In order to be certain that it's really signed by us, you need to have
727) met us in person and gotten a copy of our GPG key fingerprint, or you
728) need to know somebody who has. If you're concerned about an attack on
729) this level, we recommend you get involved with the security community
730) and start meeting people.

731) </p>

732) 

733) <hr />
734) 

735) <a id="EverybodyARelay"></a>
736) <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
737) user be a relay.</a></h3>
738) 
739) <p>
740) Requiring every Tor user to be a relay would help with scaling the

741) network to handle all our users, and <a href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#RelayAnonymity">running a Tor

742) relay may help your anonymity</a>. However, many Tor users cannot be good
743) relays &mdash; for example, some Tor clients operate from behind restrictive
744) firewalls, connect via modem, or otherwise aren't in a position where they
745) can relay traffic. Providing service to these clients is a critical

746) part of providing effective anonymity for everyone, since many Tor users
747) are subject to these or similar constraints and including these clients
748) increases the size of the anonymity set.
749) </p>
750) 
751) <p>
752) That said, we do want to encourage Tor users to run relays, so what we
753) really want to do is simplify the process of setting up and maintaining

754) a relay. We've made a lot of progress with easy configuration in the past
755) few years: Vidalia has an easy relay configuration interface, and supports
756) uPnP too. Tor is good at automatically detecting whether it's reachable and
757) how much bandwidth it can offer.

758) </p>
759) 
760) <p>
761) There are five steps we need to address before we can do this though:
762) </p>
763) 
764) <p>

765) First, we need to make Tor stable as a relay on all common
766) operating systems. The main remaining platform is Windows,
767) and we plan to finally address that in 2009. See Section 4.1 of <a
768) href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
769) development roadmap</a>.

770) </p>
771) 
772) <p>

773) Second, we still need to get better at automatically estimating
774) the right amount of bandwidth to allow. See item #7 on the
775) <a href="<page volunteer>#Research">research section of the
776) volunteer page</a>: "Tor doesn't work very well when relays
777) have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a
778) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#TransportIPnotTCP">switching
779) to UDP transport</a> is the simplest answer here &mdash; which alas is
780) not a very simple answer at all.

781) </p>
782) 
783) <p>

784) Third, we need to work on scalability, both of the network (how to
785) stop requiring that all Tor relays be able to connect to all Tor
786) relays) and of the directory (how to stop requiring that all Tor
787) users know about all Tor relays). Changes like this can have large
788) impact on potential and actual anonymity. See Section 5 of the <a
789) href="<svnsandbox>doc/design-paper/challenges.pdf">Challenges</a> paper
790) for details. Again, UDP transport would help here.

791) </p>
792) 
793) <p>

794) Fourth, we need to better understand the risks from
795) letting the attacker send traffic through your relay while
796) you're also initiating your own anonymized traffic. <a
797) href="http://freehaven.net/anonbib/#back01">Three</a> <a
798) href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
799) <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
800) describe ways to identify the relays in a circuit by running traffic
801) through candidate relays and looking for dips in the traffic while the
802) circuit is active. These clogging attacks are not that scary in the Tor
803) context so long as relays are never clients too. But if we're trying to
804) encourage more clients to turn on relay functionality too (whether as
805) <a href="<page bridges>">bridge relays</a> or as normal relays), then
806) we need to understand this threat better and learn how to mitigate it.

807) </p>
808) 
809) <p>
810) Fifth, we might need some sort of incentive scheme to encourage people
811) to relay traffic for others, and/or to become exit nodes. Here are our

812) <a href="https://blog.torproject.org/blog/two-incentive-designs-tor">current
813) thoughts on Tor incentives</a>.

814) </p>
815) 
816) <p>
817) Please help on all of these!
818) </p>
819) 
820) <hr />
821) 

822) <a id="Criminals"></a>
823) <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
824) things?</a></h3>
825) 
826) <p>
827) For the answer to this question and others, please see our new <a

828) href="<page faq-abuse>">Tor Abuse FAQ</a>.

829) </p>
830) 
831) <hr />
832) 
833) <a id="RespondISP"></a>
834) <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
835) exit relay?</a></h3>
836) 
837) <p>
838) A collection of templates for successfully responding to ISPs is <a
839) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorAbuseTemplates">collected
840) here</a>.
841) </p>
842) 

843) <hr />

844) 

845)   </div><!-- #main -->

846) 
847) #include <foot.wmi>