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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="#Virus">Why does my Tor executable appear to have a virus or
39) 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>Abuse</p>
57) <ul>
58) <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
59) <li><a href="#RespondISP">How do I respond to my ISP about my exit
60) relay?</a></li>
61) </ul>
62) 

63) <p>For other questions not yet on this version of the FAQ, see the <a
64) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ">wiki
65) FAQ</a> for now.</p>
66) 

67) <hr />
68) 
69) <a id="General"></a>
70) 

71) <a id="WhatIsTor"></a>
72) <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
73) 
74) <p>
75) The name "Tor" can refer to several different components.
76) </p>
77) 
78) <p>
79) The Tor software is a program you can run on your computer that helps keep
80) you safe on the Internet. Tor protects you by bouncing your communications
81) around a distributed network of relays run by volunteers all around
82) the world: it prevents somebody watching your Internet connection from
83) learning what sites you visit, and it prevents the sites you visit
84) from learning your physical location. This set of volunteer relays is
85) called the Tor network. You can read more about how Tor works on the <a
86) href="<page overview>">overview page</a>.
87) </p>
88) 
89) <p>
90) The Tor Project is a non-profit (charity) organization that maintains

91) and develops the Tor software.

92) </p>
93) 

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

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

97) 
98) <p>
99) There are two pieces to "Torifying" a program: connection-level anonymity
100) and application-level anonymity. Connection-level anonymity focuses on

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

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

110) </p>
111) 
112) <p>

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

119) </p>
120) 
121) <p>

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

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

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

131) </p>
132) 
133) <a id="WhyCalledTor"></a>
134) <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
135) 
136) <p>

137) Because Tor is the onion routing network. When we were starting the
138) new next-generation design and implementation of onion routing in
139) 2001-2002, we would tell people we were working on onion routing,
140) and they would say "Neat. Which one?" Even if onion routing has
141) become a standard household term, Tor was born out of the actual <a
142) href="http://www.onion-router.net/">onion routing project</a> run by
143) the Naval Research Lab.

144) </p>
145) 
146) <p>

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

148) </p>
149) 
150) <p>

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

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

156) </p>
157) 
158) <a id="Backdoor"></a>
159) <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
160) 
161) <p>

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

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

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

165) ask us, we will fight them, and (the lawyers say) probably win.
166) </p>
167) 
168) <p>
169) We think that putting a backdoor in Tor would be tremendously
170) irresponsible to our users, and a bad precedent for security software

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

173) trust our software ever again — for excellent reason!
174) </p>
175) 
176) <p>
177) But that said, there are still plenty of subtle attacks

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

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

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

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

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

187) </p>
188) 
189) <p>
190) Also, there might be accidental bugs in Tor that could affect your

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

193) </p>
194) 
195) <a id="DistributingTor"></a>
196) <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on

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

198) 
199) <p>
200) Yes.
201) </p>
202) 
203) <p>

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

205) means we give you the rights to redistribute the Tor software, either
206) modified or unmodified, either for a fee or gratis. You don't have to
207) ask us for specific permission.
208) </p>
209) 
210) <p>
211) However, if you want to redistribute the Tor software you must follow our

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

213) Essentially this means that you need to include our LICENSE file along
214) with whatever part of the Tor software you're distributing.
215) </p>
216) 
217) <p>
218) Most people who ask us this question don't want to distribute just the
219) Tor software, though. They want to distribute the Tor bundles, which
220) typically include <a href="http://www.privoxy.org/">Privoxy</a>
221) and <a href="http://www.vidalia-project.net/">Vidalia</a>.
222) You will need to follow the licenses for those programs
223) as well. Both of them are distributed under the <a

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

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

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

236) who makes it, and what properties it provides (and doesn't provide). See
237) our <a href="<page trademark-faq>">trademark FAQ</a> for details.
238) </p>
239) 
240) <p>
241) Lastly, you should realize that we release new versions of the
242) Tor software frequently, and sometimes we make backward incompatible
243) changes. So if you distribute a particular version of the Tor software, it
244) may not be supported &mdash; or even work &mdash; six months later. This
245) is a fact of life for all security software under heavy development.
246) </p>
247) 
248) <a id="SupportMail"></a>
249) <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
250) Tor support mail?</a></h3>
251) 
252) <p>
253) Many people send the Tor developers mail privately, or send mail to

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

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

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

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

289) mailing list and answer questions from others.
290) </p>
291) 
292) <a id="WhySlow"></a>
293) <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
294) 
295) <p>
296) There are many reasons why the Tor network is currently slow.
297) </p>
298) 
299) <p>
300) Before we answer, though, you should realize that Tor is never going to
301) be blazing fast. Your traffic is bouncing through volunteers' computers
302) in various parts of the world, and some bottlenecks and network latency
303) will always be present. You shouldn't expect to see university-style
304) bandwidth through Tor.
305) </p>
306) 
307) <p>
308) But that doesn't mean that it can't be improved. The current Tor network
309) is quite small compared to the number of people trying to use it, and
310) many of these users don't understand or care that Tor can't currently
311) handle file-sharing traffic load.
312) </p>
313) 
314) <p>
315) What can you do to help?
316) </p>
317) 
318) <ul>
319) 
320) <li>
321) <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
322) for others</a>. Help make the Tor network large enough that we can handle
323) all the users who want privacy and security on the Internet.
324) </li>
325) 
326) <li>
327) <a href="<page gui/index>">Help us make Tor more usable</a>. We
328) especially need people to help make it easier to configure your Tor
329) as a relay. Also, we need help with clear simple documentation to
330) walk people through setting it up.
331) </li>
332) 
333) <li>
334) There are some bottlenecks in the current Tor network. Help us design
335) experiments to track down and demonstrate where the problems are, and
336) then we can focus better on fixing them.
337) </li>
338) 
339) <li>
340) There are some steps that individuals
341) can take to improve their Tor performance. <a
342) href="https://wiki.torproject.org/noreply/TheOnionRouter/FireFoxTorPerf">You
343) can configure your Firefox to handle Tor better</a>, <a
344) href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
345) Polipo with Tor</a>, or you can try <a href="<page download>">upgrading
346) to the latest version of Tor</a>.  If this works well, please help by
347) documenting what you did, and letting us know about it.
348) </li>
349) 
350) <li>
351) Tor needs some architectural changes too. One important change is to

352) start providing <a
353) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#EverybodyARelay">better
354) service to people who relay traffic</a>. We're working on this, and
355) we'll finish faster if we get to spend more time on it.

356) </li>
357) 
358) <li>
359) Help do other things so we can do the hard stuff. Please take a moment
360) to figure out what your skills and interests are, and then <a href="<page
361) volunteer>">look at our volunteer page</a>.
362) </li>
363) 
364) <li>
365) Help find sponsors for Tor. Do you work at a company or government agency
366) that uses Tor or has a use for Internet privacy, e.g. to browse the
367) competition's websites discreetly, or to connect back to the home servers
368) when on the road without revealing affiliations? If your organization has
369) an interest in keeping the Tor network working, please contact them about
370) supporting Tor. Without sponsors, Tor is going to become even slower.
371) </li>
372) 
373) <li>
374) If you can't help out with any of the above, you can still help out
375) individually by <a href="<page donate>">donating a bit of money to the
376) cause</a>. It adds up!
377) </li>
378) 
379) </ul>
380) 
381) <a id="Funding"></a>

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

383) more funding?</a></h3>
384) 
385) <p>
386) We have about 1500 relays right now, pushing over 150 MB/s average
387) traffic. We have several hundred thousand active users. But the Tor
388) network is not yet self-sustaining.
389) </p>
390) 
391) <p>
392) There are six main development/maintenance pushes that need attention:
393) </p>
394) 
395) <ul>
396) 
397) <li>
398) Scalability: We need to keep scaling and decentralizing the Tor
399) architecture so it can handle thousands of relays and millions of
400) users. The upcoming stable release is a major improvement, but there's
401) lots more to be done next in terms of keeping Tor fast and stable.
402) </li>
403) 
404) <li>
405) User support: With this many users, a lot of people are asking questions
406) all the time, offering to help out with things, and so on. We need good
407) clean docs, and we need to spend some effort coordinating volunteers.
408) </li>
409) 
410) <li>
411) Relay support: the Tor network is run by volunteers, but they still need
412) attention with prompt bug fixes, explanations when things go wrong,
413) reminders to upgrade, and so on. The network itself is a commons, and
414) somebody needs to spend some energy making sure the relay operators stay
415) happy. We also need to work on <a href="#RelayOS">stability</a> on some
416) platforms &mdash; e.g., Tor relays have problems on Win XP currently.
417) </li>
418) 
419) <li>
420) Usability: Beyond documentation, we also need to work on usability of the
421) software itself. This includes installers, clean GUIs, easy configuration
422) to interface with other applications, and generally automating all of
423) the difficult and confusing steps inside Tor. We've got a start on this
424) with the <a href="<page gui/index>">GUI Contest</a>, but much more work
425) remains &mdash; usability for privacy software has never been easy.
426) </li>
427) 
428) <li>
429) Incentives: We need to work on ways to encourage people to configure
430) their Tors as relays and exit nodes rather than just clients.
431) <a href="#EverybodyARelay">We need to make it easy to become a relay,
432) and we need to give people incentives to do it.</a>
433) </li>
434) 
435) <li>
436) Research: The anonymous communications field is full
437) of surprises and gotchas. In our copious free time, we
438) also help run top anonymity and privacy conferences like <a
439) href="http://petsymposium.org/">PETS</a>. We've identified a set of
440) critical <a href="<page volunteer>#Research">Tor research questions</a>
441) that will help us figure out how to make Tor secure against the variety of
442) attacks out there. Of course, there are more research questions waiting
443) behind these.
444) </li>
445) 
446) </ul>
447) 
448) <p>
449) We're continuing to move forward on all of these, but at this rate
450) <a href="#WhySlow">the Tor network is growing faster than the developers
451) can keep up</a>.
452) Now would be an excellent time to add a few more developers to the effort
453) so we can continue to grow the network.
454) </p>
455) 
456) <p>
457) We are also excited about tackling related problems, such as
458) censorship-resistance.
459) </p>
460) 
461) <p>
462) We are proud to have <a href="<page sponsors>">sponsorship and support</a>
463) from the Omidyar Network, the International Broadcasting Bureau, Bell
464) Security Solutions, the Electronic Frontier Foundation, several government
465) agencies and research groups, and hundreds of private contributors.
466) </p>
467) 
468) <p>
469) However, this support is not enough to keep Tor abreast of changes in the
470) Internet privacy landscape. Please <a href="<page donate>">donate</a>
471) to the project, or <a href="<page contact>">contact</a> our executive
472) director for information on making grants or major donations.
473) </p>
474) 
475) <hr />
476) 

477) <a id="HowUninstallTor"></a>
478) <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
479) 
480) <p>
481) This depends entirely on how you installed it and which operating system you
482) have. If you installed a package, then hopefully your package has a way to

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

484) completely remove Tor, Vidalia, Torbutton for Firefox, and Privoxy on any
485) version of Windows is as follows:
486) </p>
487) 
488) <ol>
489) <li>In your taskbar, right click on Privoxy (the blue icon with a white "P")
490) and choose exit.</li>
491) <li>In your taskbar, right click on Vidalia (the green onion or the black head)
492) and choose exit.</li>
493) <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
494) Process List. If it's running, right click and choose End Process.</li>
495) <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
496) This will remove the Vidalia bundle, which includes Tor and Privoxy.</li>
497) <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
498) Click the Uninstall button.</li>

499) </ol>

500) 
501) <p>

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

505) </p>
506) 
507) <p>
508) For Mac OS X, follow the <a

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

510) </p>
511) 
512) <p>
513) If you installed by source, I'm afraid there is no easy uninstall method. But
514) on the bright side, by default it only installs into /usr/local/ and it should
515) be pretty easy to notice things there.
516) </p>
517) 
518) <hr />
519) 

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

523) 
524) <p>
525) These are PGP signatures, so you can verify that the file you've downloaded is
526) exactly the one that we intended you to get.
527) </p>
528) 
529) <p>
530) Please read the <a
531) href="https://wiki.torproject.org/noreply/TheOnionRouter/VerifyingSignatures">verifying
532) signatures</a> page for details.
533) </p>
534) 
535) <hr />
536) 
537) <a id="CompileTorWindows"></a>
538) <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
539) Windows?</a></h3>
540) 
541) <p>
542) Try following the steps at <a

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

544) </p>
545) 

546) <p>
547) (Note that you don't need to compile Tor yourself in order to use
548) it. Most people just use the packages available on the <a href="<page
549) download>">download page</a>.)
550) </p>
551) 

552) <hr />
553) 
554) <a id="Virus"></a>
555) <h3><a class="anchor" href="#Virus">Why does my Tor executable appear to have a
556) virus or spyware?</a></h3>
557) 
558) <p>
559) Sometimes, overzealous Windows virus and spyware detectors trigger on some
560) parts of the Tor Windows binary. Our best guess is that these are false

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

562) guessing game anyway. You should contact your vendor and explain that you have
563) a program that seems to be triggering false positives. Or pick a better vendor.
564) </p>
565) 
566) <p>

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

570) </p>
571) 
572) <hr />
573) 
574) <a id="LiveCD"></a>
575) <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
576) includes Tor?</a></h3>
577) 
578) <p>
579) There isn't any official LiveCD at this point. We're still trying to find good
580) solutions and trying to understand the security and anonymity implications of
581) the various options. In the mean time, feel free to check out the list below
582) and use your best judgement:
583) </p>
584) 
585) <p>

586) LiveCDs:

587) </p>
588) 
589) <ol>
590) <li><a href="http://incognito.anonymityanywhere.com/">Incognito LiveCD/USB</a>
591) is a CD you can boot that has several Internet applications (Firefox, IRC,
592) Mail, etc) pre-configured to use Tor. For most computers everything is
593) automatically configured and you're ready to go. You can even copy the CD to a
594) USB drive. Includes TorK.</li>

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

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

603) </ol>
604) 
605) <p>
606) Windows bundles:
607) </p>
608) 
609) <ol>

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

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

621) </ol>
622) 
623) <p>
624) Not currently maintained as far as we know:
625) </p>
626) 
627) <ol>

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

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

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

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

652) <p>
653) Please contact us if you know any others.
654) </p>
655) 

656) <hr />
657) 

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

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

661) 
662) <p>

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

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

668) </p>
669) 
670) <p>
671) <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
672) so observers can't look inside to see which circuit a given cell is
673) intended for. Further, the Tor client establishes an ephemeral encryption
674) key with each relay in the circuit, so only the exit relay can read
675) the cells. Both sides discard the circuit key when the circuit ends,
676) so logging traffic and then breaking into the relay to discover the key
677) won't work.
678) </p>
679) 
680) <p>
681) <b>Authentication</b>:
682) Every Tor relay has a public decryption key called the "onion key".
683) When the Tor client establishes circuits, at each step it <a
684) href="<svnsandbox>doc/design-paper/tor-design.html#subsec:circuits">demands
685) that the Tor relay prove knowledge of its onion key</a>. That way

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

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

688) </p>
689) 
690) <p>

691) <b>Coordination</b>:

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

693) have the right keys for them? Each relay has a long-term public signing
694) key called the "identity key". Each directory authority additionally has a
695) "directory signing key". The directory authorities provide a signed list
696) of all the known relays, and in that list are a set of certificates from
697) each relay (self-signed by their identity key) specifying their keys,
698) locations, exit policies, and so on. So unless the adversary can control
699) a threshold of the directory authorities, he can't trick the Tor client
700) into using other Tor relays.

701) </p>
702) 
703) <p>

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

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

709) 

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

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

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

717) 

718) <p>

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

724) </p>

725) 

726) <hr />
727) 
728) <a id="Criminals"></a>
729) <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
730) things?</a></h3>
731) 
732) <p>
733) For the answer to this question and others, please see our new <a

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

735) </p>
736) 
737) <hr />
738) 
739) <a id="RespondISP"></a>
740) <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
741) exit relay?</a></h3>
742) 
743) <p>
744) A collection of templates for successfully responding to ISPs is <a
745) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorAbuseTemplates">collected
746) here</a>.
747) </p>
748) 

749) <hr />

750) 

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

752) 
753) #include <foot.wmi>