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

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

54)     tor-browser-<version-torbrowserbundle>_en-US.exe.asc.</p>

55) 

56)     <h3>Windows</h3>

57)     <hr>

58) 

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

62) 
63)     <p>Once it's installed, use GnuPG to import the key that signed your
64)     package. Since GnuPG for Windows is a command-line tool, you will need
65)     to use <i>cmd.exe</i>. Unless you edit your PATH environment variable,
66)     you will need to tell Windows the full path to the GnuPG program. If
67)     you installed GnuPG with the default values, the path should be
68)     something like this: <i>C:\Program Files\Gnu\GnuPg\gpg.exe</i>.</p>

69) 

70)     <p>Erinn Clark signs the Tor Browser Bundles. Import her key
71)     (0x63FEE659) by starting <i>cmd.exe</i> and typing:</p>

72) 

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

74) 

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

77) 

78)     <pre>C:\Program Files\Gnu\GnuPg\gpg.exe --fingerprint 0x63FEE659</pre>
79) 
80)     <p>You should see:</p>
81)     <pre>
82)     pub   2048R/63FEE659 2003-10-16
83)           Key fingerprint = 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659
84)     uid                  Erinn Clark &lt;erinn@torproject.org&gt;
85)     uid                  Erinn Clark &lt;erinn@debian.org&gt;
86)     uid                  Erinn Clark &lt;erinn@double-helix.org&gt;
87)     sub   2048R/EB399FD7 2003-10-16
88) </pre>

89) 

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

93) 

94)     <pre>C:\Program Files\Gnu\GnuPg\gpg.exe --verify C:\Users\Alice\Desktop\<file-win32-bundle-stable>.asc C:\Users\Alice\Desktop\<file-win32-bundle-stable></pre>
95) 
96)     <p>The output should say "Good signature": </p>
97) 
98)     <pre>
99)     gpg: Signature made Wed 31 Aug 2011 06:37:01 PM EDT using RSA key ID 63FEE659
100)     gpg: Good signature from "Erinn Clark &lt;erinn@torproject.org&gt;"
101)     gpg:                 aka "Erinn Clark &lt;erinn@debian.org&gt;"
102)     gpg:                 aka "Erinn Clark &lt;erinn@double-helix.org&gt;"
103)     gpg: WARNING: This key is not certified with a trusted signature!
104)     gpg:          There is no indication that the signature belongs to the owner.
105)     Primary key fingerprint: 8738 A680 B84B 3031 A630  F2DB 416F 0610 63FE E659
106)     </pre>
107) 
108)     <p>
109)     Notice that there is a warning because you haven't assigned a trust
110)     index to this person. This means that GnuPG verified that the key made
111)     that signature, but it's up to you to decide if that key really belongs
112)     to the developer. The best method is to meet the developer in person and
113)     exchange key fingerprints.
114)     </p>

115) 

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

117)     <hr>

118) 

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

123) 

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

128) 

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

130) 

131)     <p>After importing the key, you can verify that the fingerprint
132)     is correct:</p>
133) 
134)     <pre>gpg --fingerprint 0x63FEE659</pre>

135) 

136)     <p>You should see:</p>
137)     <pre>

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

145) 

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

149) 

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

151) 

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

153) 

154)     <pre>

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

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

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

162)     </pre>

163) 

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

171) 

172)     <h3>Linux</h3>
173)     <hr>

174) 

175)     <p>For <b>RPM-based distributions</b> you can manually verify the
176)     signatures on the RPM packages by:</p>
177)     <pre>rpm -K filename.rpm</pre>

178) 

179)     <p>For <b>Debian</b>, you should read the instructions on <a
180)     href="<page docs/debian>#packages">importing these keys to
181)     apt</a>.</p>

182) 

183)     <p>If you wish to learn more about GPG, see <a
184)     href="http://www.gnupg.org/documentation/">http://www.gnupg.org/documentation/</a>.</p>

185) 

186)   </div>
187)   <!-- END MAINCOL -->
188)   <div id = "sidecol">
189) #include "side.wmi"
190) #include "info.wmi"
191)   </div>
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