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bf740959 | 1 | .\" -*- nroff -*- |
2 | .\" | |
bf740959 | 3 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
bf740959 | 4 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
5 | .\" All rights reserved | |
6 | .\" | |
bcbf86ec | 7 | .\" As far as I am concerned, the code I have written for this software |
8 | .\" can be used freely for any purpose. Any derived versions of this | |
9 | .\" software must be clearly marked as such, and if the derived work is | |
10 | .\" incompatible with the protocol description in the RFC file, it must be | |
11 | .\" called by a name other than "ssh" or "Secure Shell". | |
12 | .\" | |
13 | .\" | |
14 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. | |
15 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. | |
16 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. | |
17 | .\" | |
18 | .\" Redistribution and use in source and binary forms, with or without | |
19 | .\" modification, are permitted provided that the following conditions | |
20 | .\" are met: | |
21 | .\" 1. Redistributions of source code must retain the above copyright | |
22 | .\" notice, this list of conditions and the following disclaimer. | |
23 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
24 | .\" notice, this list of conditions and the following disclaimer in the | |
25 | .\" documentation and/or other materials provided with the distribution. | |
bf740959 | 26 | .\" |
bcbf86ec | 27 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
28 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
29 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
30 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
31 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
32 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
33 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
34 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
35 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
36 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
bf740959 | 37 | .\" |
38 | .Dd September 25, 1999 | |
39 | .Dt SSH-KEYGEN 1 | |
40 | .Os | |
41 | .Sh NAME | |
42 | .Nm ssh-keygen | |
43 | .Nd authentication key generation | |
44 | .Sh SYNOPSIS | |
45 | .Nm ssh-keygen | |
1d1ffb87 | 46 | .Op Fl dq |
bf740959 | 47 | .Op Fl b Ar bits |
48 | .Op Fl N Ar new_passphrase | |
49 | .Op Fl C Ar comment | |
7cd3766c | 50 | .Op Fl f Ar output_keyfile |
bf740959 | 51 | .Nm ssh-keygen |
52 | .Fl p | |
53 | .Op Fl P Ar old_passphrase | |
54 | .Op Fl N Ar new_passphrase | |
f095fcc7 | 55 | .Op Fl f Ar keyfile |
bf740959 | 56 | .Nm ssh-keygen |
1d1ffb87 | 57 | .Fl x |
7cd3766c | 58 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 59 | .Nm ssh-keygen |
60 | .Fl X | |
7cd3766c | 61 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 62 | .Nm ssh-keygen |
63 | .Fl y | |
7cd3766c | 64 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 65 | .Nm ssh-keygen |
bf740959 | 66 | .Fl c |
67 | .Op Fl P Ar passphrase | |
68 | .Op Fl C Ar comment | |
f095fcc7 | 69 | .Op Fl f Ar keyfile |
70 | .Nm ssh-keygen | |
71 | .Fl l | |
7cd3766c | 72 | .Op Fl f Ar input_keyfile |
a306f2dd | 73 | .Nm ssh-keygen |
74 | .Fl R | |
f54651ce | 75 | .Sh DESCRIPTION |
bf740959 | 76 | .Nm |
f54651ce | 77 | generates and manages authentication keys for |
bf740959 | 78 | .Xr ssh 1 . |
1d1ffb87 | 79 | .Nm |
80 | defaults to generating an RSA key for use by protocols 1.3 and 1.5; | |
81 | specifying the | |
82 | .Fl d | |
83 | flag will create a DSA key instead for use by protocol 2.0. | |
84 | .Pp | |
bf740959 | 85 | Normally each user wishing to use SSH |
1d1ffb87 | 86 | with RSA or DSA authentication runs this once to create the authentication |
bf740959 | 87 | key in |
1d1ffb87 | 88 | .Pa $HOME/.ssh/identity |
89 | or | |
90 | .Pa $HOME/.ssh/id_dsa . | |
91 | Additionally, the system administrator may use this to generate host keys, | |
92 | as seen in | |
93 | .Pa /etc/rc . | |
bf740959 | 94 | .Pp |
95 | Normally this program generates the key and asks for a file in which | |
4fe2af09 | 96 | to store the private key. |
97 | The public key is stored in a file with the same name but | |
bf740959 | 98 | .Dq .pub |
4fe2af09 | 99 | appended. |
100 | The program also asks for a passphrase. | |
101 | The passphrase may be empty to indicate no passphrase | |
bf740959 | 102 | (host keys must have empty passphrase), or it may be a string of |
4fe2af09 | 103 | arbitrary length. |
104 | Good passphrases are 10-30 characters long and are | |
bf740959 | 105 | not simple sentences or otherwise easily guessable (English |
106 | prose has only 1-2 bits of entropy per word, and provides very bad | |
4fe2af09 | 107 | passphrases). |
108 | The passphrase can be changed later by using the | |
bf740959 | 109 | .Fl p |
110 | option. | |
111 | .Pp | |
4fe2af09 | 112 | There is no way to recover a lost passphrase. |
113 | If the passphrase is | |
bf740959 | 114 | lost or forgotten, you will have to generate a new key and copy the |
115 | corresponding public key to other machines. | |
116 | .Pp | |
1d1ffb87 | 117 | For RSA, there is also a comment field in the key file that is only for |
4fe2af09 | 118 | convenience to the user to help identify the key. |
119 | The comment can tell what the key is for, or whatever is useful. | |
120 | The comment is initialized to | |
bf740959 | 121 | .Dq user@host |
122 | when the key is created, but can be changed using the | |
123 | .Fl c | |
124 | option. | |
125 | .Pp | |
1d1ffb87 | 126 | After a key is generated, instructions below detail where the keys |
127 | should be placed to be activated. | |
128 | .Pp | |
bf740959 | 129 | The options are as follows: |
130 | .Bl -tag -width Ds | |
131 | .It Fl b Ar bits | |
4fe2af09 | 132 | Specifies the number of bits in the key to create. |
133 | Minimum is 512 bits. | |
134 | Generally 1024 bits is considered sufficient, and key sizes | |
135 | above that no longer improve security but make things slower. | |
136 | The default is 1024 bits. | |
bf740959 | 137 | .It Fl c |
138 | Requests changing the comment in the private and public key files. | |
139 | The program will prompt for the file containing the private keys, for | |
140 | passphrase if the key has one, and for the new comment. | |
f095fcc7 | 141 | .It Fl f |
142 | Specifies the filename of the key file. | |
143 | .It Fl l | |
144 | Show fingerprint of specified private or public key file. | |
bf740959 | 145 | .It Fl p |
146 | Requests changing the passphrase of a private key file instead of | |
4fe2af09 | 147 | creating a new private key. |
148 | The program will prompt for the file | |
bf740959 | 149 | containing the private key, for the old passphrase, and twice for the |
150 | new passphrase. | |
151 | .It Fl q | |
152 | Silence | |
153 | .Nm ssh-keygen . | |
154 | Used by | |
155 | .Pa /etc/rc | |
156 | when creating a new key. | |
157 | .It Fl C Ar comment | |
158 | Provides the new comment. | |
159 | .It Fl N Ar new_passphrase | |
160 | Provides the new passphrase. | |
161 | .It Fl P Ar passphrase | |
162 | Provides the (old) passphrase. | |
a306f2dd | 163 | .It Fl R |
164 | If RSA support is functional, immediately exits with code 0. If RSA | |
165 | support is not functional, exits with code 1. This flag will be | |
166 | removed once the RSA patent expires. | |
1d1ffb87 | 167 | .It Fl x |
168 | This option will read a private | |
d0c832f3 | 169 | OpenSSH DSA format file and print a SSH2-compatible public key to stdout. |
1d1ffb87 | 170 | .It Fl X |
171 | This option will read a | |
d0c832f3 | 172 | SSH2-compatible public key file and print an OpenSSH DSA compatible public key to stdout. |
1d1ffb87 | 173 | .It Fl y |
174 | This option will read a private | |
d0c832f3 | 175 | OpenSSH DSA format file and print an OpenSSH DSA public key to stdout. |
bf740959 | 176 | .El |
177 | .Sh FILES | |
178 | .Bl -tag -width Ds | |
bf740959 | 179 | .It Pa $HOME/.ssh/identity |
4fe2af09 | 180 | Contains the RSA authentication identity of the user. |
181 | This file should not be readable by anyone but the user. | |
182 | It is possible to | |
bf740959 | 183 | specify a passphrase when generating the key; that passphrase will be |
4fe2af09 | 184 | used to encrypt the private part of this file using 3DES. |
185 | This file is not automatically accessed by | |
bf740959 | 186 | .Nm |
187 | but it is offered as the default file for the private key. | |
1d1ffb87 | 188 | .Xr sshd 8 |
189 | will read this file when a login attempt is made. | |
bf740959 | 190 | .It Pa $HOME/.ssh/identity.pub |
4fe2af09 | 191 | Contains the public key for authentication. |
192 | The contents of this file should be added to | |
bf740959 | 193 | .Pa $HOME/.ssh/authorized_keys |
194 | on all machines | |
4fe2af09 | 195 | where you wish to log in using RSA authentication. |
196 | There is no need to keep the contents of this file secret. | |
1d1ffb87 | 197 | .It Pa $HOME/.ssh/id_dsa |
198 | Contains the DSA authentication identity of the user. | |
199 | This file should not be readable by anyone but the user. | |
200 | It is possible to | |
201 | specify a passphrase when generating the key; that passphrase will be | |
202 | used to encrypt the private part of this file using 3DES. | |
203 | This file is not automatically accessed by | |
204 | .Nm | |
205 | but it is offered as the default file for the private key. | |
206 | .Xr sshd 8 | |
207 | will read this file when a login attempt is made. | |
208 | .It Pa $HOME/.ssh/id_dsa.pub | |
209 | Contains the public key for authentication. | |
210 | The contents of this file should be added to | |
211 | .Pa $HOME/.ssh/authorized_keys2 | |
212 | on all machines | |
213 | where you wish to log in using DSA authentication. | |
214 | There is no need to keep the contents of this file secret. | |
089fbbd2 | 215 | .El |
bf740959 | 216 | .Sh AUTHOR |
217 | Tatu Ylonen <ylo@cs.hut.fi> | |
218 | .Pp | |
219 | OpenSSH | |
220 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | |
4fe2af09 | 221 | removed and newer features re-added. |
222 | Rapidly after the 1.2.12 release, | |
223 | newer versions bore successively more restrictive licenses. | |
224 | This version of OpenSSH | |
bf740959 | 225 | .Bl -bullet |
226 | .It | |
bcbf86ec | 227 | has all components of a restrictive nature (i.e., patents, see |
228 | .Xr crypto 3 ) | |
bf740959 | 229 | directly removed from the source code; any licensed or patented components |
230 | are chosen from | |
231 | external libraries. | |
232 | .It | |
233 | has been updated to support ssh protocol 1.5. | |
234 | .It | |
f54651ce | 235 | contains added support for |
bf740959 | 236 | .Xr kerberos 8 |
237 | authentication and ticket passing. | |
238 | .It | |
239 | supports one-time password authentication with | |
240 | .Xr skey 1 . | |
241 | .El | |
bf740959 | 242 | .Sh SEE ALSO |
243 | .Xr ssh 1 , | |
244 | .Xr ssh-add 1 , | |
0c372277 | 245 | .Xr ssh-agent 1 , |
bf740959 | 246 | .Xr sshd 8 , |
bcbf86ec | 247 | .Xr crypto 3 |