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5) #include "head.wmi" TITLE="Tor Project: Verifying Signatures" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">

8)     <a href="<page index>">Home &raquo; </a>

9)     <a href="<page docs/verifying-signatures>">Verifying Signatures</a>
10)   </div>

11)   <div id="maincol">

12)     <h1>How to verify signatures for packages</h1>

13)     <hr>

14) 

15)     <h3>What is a signature and why should I check it?</h3>
16)     <hr>
17) 
18)     <p>How do you know that the Tor program you have is really the
19)     one we made? Many Tor users have very real adversaries who might
20)     try to give them a fake version of Tor &mdash; and it doesn't matter
21)     how secure and anonymous Tor is if you're not running the real Tor.</p>
22) 
23)     <p>An attacker could try a variety of attacks to get you to download
24)     a fake Tor. For example, he could trick you into thinking some other
25)     website is a great place to download Tor. That's why you should
26)     always download Tor from <b>https</b>://www.torproject.org/. The
27)     https part means there's encryption and authentication between your
28)     browser and the website, making it much harder for the attacker
29)     to modify your download. But it's not perfect. Some places in the

30)     world block the Tor website, making users try <a href="<page
31)     docs/faq>#GetTor">somewhere else</a>. Large

32)     companies sometimes force employees to use a modified browser,
33)     so the company can listen in on all their browsing. We've even <a
34)     href="https://blog.torproject.org/blog/diginotar-debacle-and-what-you-should-do-about-it">seen</a>
35)     attackers who have the ability to trick your browser into thinking
36)     you're talking to the Tor website with https when you're not.</p>
37) 
38)     <p>Some software sites list <a
39)     href="http://en.wikipedia.org/wiki/Cryptographic_hash_function">sha1
40)     hashes</a> alongside the software on their website, so users can
41)     verify that they downloaded the file without any errors. These
42)     "checksums" help you answer the question "Did I download this file
43)     correctly from whoever sent it to me?" They do a good job at making
44)     sure you didn't have any random errors in your download, but they
45)     don't help you figure out whether you were downloading it from the
46)     attacker. The better question to answer is: "Is this file that I
47)     just downloaded the file that Tor intended me to get?"</p>
48) 

49)     <p>Each file on <a href="<page download/download>">our download
50)     page</a> is accompanied by a file with the same name as the
51)     package and the extension ".asc". These .asc files are GPG
52)     signatures. They allow you to verify the file you've downloaded
53)     is exactly the one that we intended you to get. For example,
54)     tor-browser-<version-torbrowserbundle>_en-US.exe is accompanied by

55)     tor-browser-<version-torbrowserbundle>_en-US.exe.asc. For a list
56)     of which developer signs which package, see our <a href="<page
57)     docs/signing-keys>">signing keys</a> page.</p>

58) 

59)     <h3>Windows</h3>

60)     <hr>

61) 

62)     <p>You need to have GnuPG installed before
63)     you can verify signatures. Download it from <a
64)     href="http://gpg4win.org/download.html">http://gpg4win.org/download.html</a>.</p>

65) 
66)     <p>Once it's installed, use GnuPG to import the key that signed your
67)     package. Since GnuPG for Windows is a command-line tool, you will need
68)     to use <i>cmd.exe</i>. Unless you edit your PATH environment variable,
69)     you will need to tell Windows the full path to the GnuPG program. If
70)     you installed GnuPG with the default values, the path should be
71)     something like this: <i>C:\Program Files\Gnu\GnuPg\gpg.exe</i>.</p>

72) 

73)     <p>Erinn Clark signs the Tor Browser Bundles. Import her key
74)     (0x63FEE659) by starting <i>cmd.exe</i> and typing:</p>

75) 

76)     <pre>C:\Program Files\Gnu\GnuPg\gpg.exe --keyserver hkp://keys.gnupg.net --recv-keys 0x63FEE659</pre>

77) 

78)     <p>After importing the key, you can verify that the fingerprint
79)     is correct:</p>

80) 

81)     <pre>C:\Program Files\Gnu\GnuPg\gpg.exe --fingerprint 0x63FEE659</pre>
82) 
83)     <p>You should see:</p>
84)     <pre>
85)     pub   2048R/63FEE659 2003-10-16
86)           Key fingerprint = 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659
87)     uid                  Erinn Clark &lt;erinn@torproject.org&gt;
88)     uid                  Erinn Clark &lt;erinn@debian.org&gt;
89)     uid                  Erinn Clark &lt;erinn@double-helix.org&gt;
90)     sub   2048R/EB399FD7 2003-10-16
91) </pre>

92) 

93)     <p>To verify the signature of the package you downloaded, you will need
94)     to download the ".asc" file as well. Assuming you downloaded the
95)     package and its signature to your Desktop, run:</p>

96) 

97)     <pre>C:\Program Files\Gnu\GnuPg\gpg.exe --verify C:\Users\Alice\Desktop\<file-win32-bundle-stable>.asc</pre>

98) 
99)     <p>The output should say "Good signature": </p>
100) 
101)     <pre>
102)     gpg: Signature made Wed 31 Aug 2011 06:37:01 PM EDT using RSA key ID 63FEE659
103)     gpg: Good signature from "Erinn Clark &lt;erinn@torproject.org&gt;"
104)     gpg:                 aka "Erinn Clark &lt;erinn@debian.org&gt;"
105)     gpg:                 aka "Erinn Clark &lt;erinn@double-helix.org&gt;"
106)     gpg: WARNING: This key is not certified with a trusted signature!
107)     gpg:          There is no indication that the signature belongs to the owner.
108)     Primary key fingerprint: 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659
109)     </pre>
110) 
111)     <p>
112)     Notice that there is a warning because you haven't assigned a trust
113)     index to this person. This means that GnuPG verified that the key made
114)     that signature, but it's up to you to decide if that key really belongs
115)     to the developer. The best method is to meet the developer in person and
116)     exchange key fingerprints.
117)     </p>

118) 

119)     <h3>Mac OS X</h3>

120)     <hr>

121) 

122)     <p>You need to have GnuPG installed before you can verify
123)     signatures. You can install it from <a
124)     href="http://macgpg.sourceforge.net/">http://macgpg.sourceforge.net/</a>.
125)     </p>

126) 

127)     <p>Once it's installed, use GnuPG to import the key that signed
128)     your package. Erinn Clark signs the Tor Browser Bundles. Import her
129)     key (0x63FEE659) by starting the terminal (under "Applications")
130)     and typing:</p>

131) 

132)     <pre>gpg --keyserver hkp://keys.gnupg.net --recv-keys 0x63FEE659</pre>

133) 

134)     <p>After importing the key, you can verify that the fingerprint
135)     is correct:</p>
136) 
137)     <pre>gpg --fingerprint 0x63FEE659</pre>

138) 

139)     <p>You should see:</p>
140)     <pre>

141)     pub   2048R/63FEE659 2003-10-16
142)           Key fingerprint = 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659
143)     uid                  Erinn Clark <erinn@torproject.org>
144)     uid                  Erinn Clark <erinn@debian.org>
145)     uid                  Erinn Clark <erinn@double-helix.org>
146)     sub   2048R/EB399FD7 2003-10-16
147)     </pre>

148) 

149)     <p>To verify the signature of the package you downloaded, you will need
150)     to download the ".asc" file as well. Assuming you downloaded the
151)     package and its signature to your Desktop, run:</p>

152) 

153)     <pre>gpg --verify /Users/Alice/<file-osx-x86-bundle-stable>.asc</pre>

154) 

155)     <p>The output should say "Good signature": </p>

156) 

157)     <pre>

158)     gpg: Signature made Wed 31 Aug 2011 06:37:01 PM EDT using RSA key ID 63FEE659
159)     gpg: Good signature from "Erinn Clark <erinn@torproject.org>"
160)     gpg:                 aka "Erinn Clark <erinn@debian.org>"
161)     gpg:                 aka "Erinn Clark <erinn@double-helix.org>"

162)     gpg: WARNING: This key is not certified with a trusted signature!
163)     gpg:          There is no indication that the signature belongs to the owner.

164)     Primary key fingerprint: 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659

165)     </pre>

166) 

167)     <p>
168)     Notice that there is a warning because you haven't assigned a trust
169)     index to this person. This means that GnuPG verified that the key made
170)     that signature, but it's up to you to decide if that key really belongs
171)     to the developer. The best method is to meet the developer in person and
172)     exchange key fingerprints.
173)     </p>

174) 

175)     <h3>Linux</h3>
176)     <hr>

177) 

178)     <p>Most Linux distributions come with gpg preinstalled, so users
179)     who want to verify the Tor Browser Bundle for Linux (or the source
180)     tarball) can just follow along with the instructions above for
181)     "Mac OS X".</p>

182) 

183)     <p>If you're using the <b>Debian</b> packages, you should read the
184)     instructions on <a href="<page docs/debian>#packages">importing
185)     these keys to apt</a>.</p>

186) 

187)     <p>If you're using the <b>RPMs</b>, you can manually verify the
188)     signatures on the RPM packages by <pre>rpm -K filename.rpm</pre></p>
189) 
190)     <p>See <a
191)     href="http://www.gnupg.org/documentation/">http://www.gnupg.org/documentation/</a>
192)     to learn more about GPG.</p>

193) 

194)   </div>
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196)   <div id = "sidecol">
197) #include "side.wmi"
198) #include "info.wmi"
199)   </div>
200)   <!-- END SIDECOL -->
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