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c35a6dc5 | 1 | .\" $OpenBSD: ssh-keygen.1,v 1.60 2003/07/28 09:49:56 djm Exp $ |
23c2a7a5 | 2 | .\" |
bf740959 | 3 | .\" -*- nroff -*- |
4 | .\" | |
bf740959 | 5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
bf740959 | 6 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
7 | .\" All rights reserved | |
8 | .\" | |
bcbf86ec | 9 | .\" As far as I am concerned, the code I have written for this software |
10 | .\" can be used freely for any purpose. Any derived versions of this | |
11 | .\" software must be clearly marked as such, and if the derived work is | |
12 | .\" incompatible with the protocol description in the RFC file, it must be | |
13 | .\" called by a name other than "ssh" or "Secure Shell". | |
14 | .\" | |
15 | .\" | |
f3c7c613 | 16 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
17 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. | |
18 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. | |
bcbf86ec | 19 | .\" |
20 | .\" Redistribution and use in source and binary forms, with or without | |
21 | .\" modification, are permitted provided that the following conditions | |
22 | .\" are met: | |
23 | .\" 1. Redistributions of source code must retain the above copyright | |
24 | .\" notice, this list of conditions and the following disclaimer. | |
25 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
26 | .\" notice, this list of conditions and the following disclaimer in the | |
27 | .\" documentation and/or other materials provided with the distribution. | |
bf740959 | 28 | .\" |
bcbf86ec | 29 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
30 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
31 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
32 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
33 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
34 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
35 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
36 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
37 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
38 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
bf740959 | 39 | .\" |
40 | .Dd September 25, 1999 | |
41 | .Dt SSH-KEYGEN 1 | |
42 | .Os | |
43 | .Sh NAME | |
44 | .Nm ssh-keygen | |
5deceabb | 45 | .Nd authentication key generation, management and conversion |
bf740959 | 46 | .Sh SYNOPSIS |
47 | .Nm ssh-keygen | |
a4e5acef | 48 | .Bk -words |
fa08c86b | 49 | .Op Fl q |
bf740959 | 50 | .Op Fl b Ar bits |
2a55e100 | 51 | .Fl t Ar type |
bf740959 | 52 | .Op Fl N Ar new_passphrase |
53 | .Op Fl C Ar comment | |
7cd3766c | 54 | .Op Fl f Ar output_keyfile |
a4e5acef | 55 | .Ek |
bf740959 | 56 | .Nm ssh-keygen |
57 | .Fl p | |
58 | .Op Fl P Ar old_passphrase | |
59 | .Op Fl N Ar new_passphrase | |
f095fcc7 | 60 | .Op Fl f Ar keyfile |
bf740959 | 61 | .Nm ssh-keygen |
5deceabb | 62 | .Fl i |
7cd3766c | 63 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 64 | .Nm ssh-keygen |
5deceabb | 65 | .Fl e |
7cd3766c | 66 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 67 | .Nm ssh-keygen |
68 | .Fl y | |
7cd3766c | 69 | .Op Fl f Ar input_keyfile |
1d1ffb87 | 70 | .Nm ssh-keygen |
bf740959 | 71 | .Fl c |
72 | .Op Fl P Ar passphrase | |
73 | .Op Fl C Ar comment | |
f095fcc7 | 74 | .Op Fl f Ar keyfile |
75 | .Nm ssh-keygen | |
76 | .Fl l | |
aaf45d87 | 77 | .Op Fl f Ar input_keyfile |
78 | .Nm ssh-keygen | |
79 | .Fl B | |
7cd3766c | 80 | .Op Fl f Ar input_keyfile |
f0d6bdcf | 81 | .Nm ssh-keygen |
82 | .Fl D Ar reader | |
83 | .Nm ssh-keygen | |
84 | .Fl U Ar reader | |
85 | .Op Fl f Ar input_keyfile | |
21289cd0 | 86 | .Nm ssh-keygen |
87 | .Fl r Ar hostname | |
88 | .Op Fl f Ar input_keyfile | |
89 | .Op Fl g | |
c35a6dc5 | 90 | .Nm ssh-keygen |
91 | .Fl G Ar output_file | |
92 | .Op Fl b Ar bits | |
93 | .Op Fl M Ar memory | |
94 | .Op Fl S Ar start_point | |
95 | .Nm ssh-keygen | |
96 | .Fl T Ar output_file | |
97 | .Fl f Ar input_file | |
98 | .Op Fl a Ar num_trials | |
99 | .Op Fl W Ar generator | |
f54651ce | 100 | .Sh DESCRIPTION |
bf740959 | 101 | .Nm |
5deceabb | 102 | generates, manages and converts authentication keys for |
bf740959 | 103 | .Xr ssh 1 . |
1d1ffb87 | 104 | .Nm |
7203d6bb | 105 | can create RSA keys for use by SSH protocol version 1 and RSA or DSA |
3cbc677d | 106 | keys for use by SSH protocol version 2. |
107 | The type of key to be generated is specified with the | |
fa08c86b | 108 | .Fl t |
3dc93cd8 | 109 | option. |
1d1ffb87 | 110 | .Pp |
c35a6dc5 | 111 | .Nm |
112 | is also used to generate groups for use in Diffie-Hellman group | |
113 | exchange (DH-GEX). | |
114 | See the | |
115 | .Sx MODULI GENERATION | |
116 | section for details. | |
117 | .Pp | |
bf740959 | 118 | Normally each user wishing to use SSH |
1d1ffb87 | 119 | with RSA or DSA authentication runs this once to create the authentication |
bf740959 | 120 | key in |
c0ecc314 | 121 | .Pa $HOME/.ssh/identity , |
122 | .Pa $HOME/.ssh/id_dsa | |
1d1ffb87 | 123 | or |
c0ecc314 | 124 | .Pa $HOME/.ssh/id_rsa . |
1d1ffb87 | 125 | Additionally, the system administrator may use this to generate host keys, |
126 | as seen in | |
127 | .Pa /etc/rc . | |
bf740959 | 128 | .Pp |
129 | Normally this program generates the key and asks for a file in which | |
4fe2af09 | 130 | to store the private key. |
131 | The public key is stored in a file with the same name but | |
bf740959 | 132 | .Dq .pub |
4fe2af09 | 133 | appended. |
134 | The program also asks for a passphrase. | |
135 | The passphrase may be empty to indicate no passphrase | |
b5c334cc | 136 | (host keys must have an empty passphrase), or it may be a string of |
4fe2af09 | 137 | arbitrary length. |
c840d0ad | 138 | A passphrase is similar to a password, except it can be a phrase with a |
139 | series of words, punctuation, numbers, whitespace, or any string of | |
140 | characters you want. | |
141 | Good passphrases are 10-30 characters long, are | |
bf740959 | 142 | not simple sentences or otherwise easily guessable (English |
e5b71e99 | 143 | prose has only 1-2 bits of entropy per character, and provides very bad |
c840d0ad | 144 | passphrases), and contain a mix of upper and lowercase letters, |
145 | numbers, and non-alphanumeric characters. | |
4fe2af09 | 146 | The passphrase can be changed later by using the |
bf740959 | 147 | .Fl p |
148 | option. | |
149 | .Pp | |
4fe2af09 | 150 | There is no way to recover a lost passphrase. |
151 | If the passphrase is | |
91789042 | 152 | lost or forgotten, a new key must be generated and copied to the |
bf740959 | 153 | corresponding public key to other machines. |
154 | .Pp | |
5deceabb | 155 | For RSA1 keys, |
156 | there is also a comment field in the key file that is only for | |
4fe2af09 | 157 | convenience to the user to help identify the key. |
158 | The comment can tell what the key is for, or whatever is useful. | |
159 | The comment is initialized to | |
bf740959 | 160 | .Dq user@host |
161 | when the key is created, but can be changed using the | |
162 | .Fl c | |
163 | option. | |
164 | .Pp | |
1d1ffb87 | 165 | After a key is generated, instructions below detail where the keys |
166 | should be placed to be activated. | |
167 | .Pp | |
bf740959 | 168 | The options are as follows: |
169 | .Bl -tag -width Ds | |
c35a6dc5 | 170 | .It Fl a Ar trials |
171 | Specifies the number of primality tests to perform when screening DH-GEX | |
172 | candidates using the | |
173 | .Fl T | |
174 | command. | |
bf740959 | 175 | .It Fl b Ar bits |
4fe2af09 | 176 | Specifies the number of bits in the key to create. |
177 | Minimum is 512 bits. | |
63baa058 | 178 | Generally, 1024 bits is considered sufficient. |
4fe2af09 | 179 | The default is 1024 bits. |
bf740959 | 180 | .It Fl c |
181 | Requests changing the comment in the private and public key files. | |
f564d016 | 182 | This operation is only supported for RSA1 keys. |
bf740959 | 183 | The program will prompt for the file containing the private keys, for |
cf7ff074 | 184 | the passphrase if the key has one, and for the new comment. |
5deceabb | 185 | .It Fl e |
b587c165 | 186 | This option will read a private or public OpenSSH key file and |
187 | print the key in a | |
5deceabb | 188 | .Sq SECSH Public Key File Format |
189 | to stdout. | |
190 | This option allows exporting keys for use by several commercial | |
191 | SSH implementations. | |
21289cd0 | 192 | .It Fl g |
193 | Use generic DNS resource record format. | |
f0d6bdcf | 194 | .It Fl f Ar filename |
f095fcc7 | 195 | Specifies the filename of the key file. |
5deceabb | 196 | .It Fl i |
197 | This option will read an unencrypted private (or public) key file | |
198 | in SSH2-compatible format and print an OpenSSH compatible private | |
199 | (or public) key to stdout. | |
200 | .Nm | |
bcaa828e | 201 | also reads the |
5deceabb | 202 | .Sq SECSH Public Key File Format . |
203 | This option allows importing keys from several commercial | |
204 | SSH implementations. | |
f095fcc7 | 205 | .It Fl l |
f564d016 | 206 | Show fingerprint of specified public key file. |
207 | Private RSA1 keys are also supported. | |
208 | For RSA and DSA keys | |
209 | .Nm | |
210 | tries to find the matching public key file and prints its fingerprint. | |
bf740959 | 211 | .It Fl p |
212 | Requests changing the passphrase of a private key file instead of | |
4fe2af09 | 213 | creating a new private key. |
214 | The program will prompt for the file | |
bf740959 | 215 | containing the private key, for the old passphrase, and twice for the |
216 | new passphrase. | |
217 | .It Fl q | |
218 | Silence | |
219 | .Nm ssh-keygen . | |
220 | Used by | |
221 | .Pa /etc/rc | |
222 | when creating a new key. | |
5deceabb | 223 | .It Fl y |
224 | This option will read a private | |
225 | OpenSSH format file and print an OpenSSH public key to stdout. | |
fa08c86b | 226 | .It Fl t Ar type |
227 | Specifies the type of the key to create. | |
228 | The possible values are | |
229 | .Dq rsa1 | |
230 | for protocol version 1 and | |
231 | .Dq rsa | |
232 | or | |
233 | .Dq dsa | |
234 | for protocol version 2. | |
aaf45d87 | 235 | .It Fl B |
236 | Show the bubblebabble digest of specified private or public key file. | |
bf740959 | 237 | .It Fl C Ar comment |
238 | Provides the new comment. | |
f0d6bdcf | 239 | .It Fl D Ar reader |
240 | Download the RSA public key stored in the smartcard in | |
241 | .Ar reader . | |
c35a6dc5 | 242 | .It Fl G Ar output_file |
243 | Generate candidate primes for DH-GEX. | |
244 | These primes must be screened for | |
245 | safety (using the | |
246 | .Fl T | |
247 | option) before use. | |
248 | .It Fl M Ar memory | |
249 | Specify the amount of memory to use (in megabytes) when generating | |
250 | candidate moduli for DH-GEX. | |
bf740959 | 251 | .It Fl N Ar new_passphrase |
252 | Provides the new passphrase. | |
253 | .It Fl P Ar passphrase | |
254 | Provides the (old) passphrase. | |
c35a6dc5 | 255 | .It Fl S Ar start |
256 | Specify start point (in hex) when generating candidate moduli for DH-GEX. | |
257 | .It Fl T Ar output_file | |
258 | Test DH group exchange candidate primes (generated using the | |
259 | .Fl G | |
260 | option) for safety. | |
261 | .It Fl W Ar generator | |
262 | Specify desired generator when testing candidate moduli for DH-GEX. | |
f0d6bdcf | 263 | .It Fl U Ar reader |
264 | Upload an existing RSA private key into the smartcard in | |
265 | .Ar reader . | |
21289cd0 | 266 | .It Fl r Ar hostname |
267 | Print DNS resource record with the specified | |
268 | .Ar hostname . | |
bf740959 | 269 | .El |
c35a6dc5 | 270 | .Sh MODULI GENERATION |
271 | .Nm | |
272 | may be used to generate groups for the Diffie-Hellman Group Exchange | |
273 | (DH-GEX) protocol. | |
274 | Generating these groups is a two-step process: first, candidate | |
275 | primes are generated using a fast, but memory intensive process. | |
276 | These candidate primes are then tested for suitability (a CPU-intensive | |
277 | process). | |
278 | .Pp | |
279 | Generation of primes is performed using the | |
280 | .Fl G | |
281 | option. | |
282 | The desired length of the primes may be specified by the | |
283 | .Fl b | |
284 | option. | |
285 | For example: | |
286 | .Pp | |
287 | .Dl ssh-keygen -G moduli-2048.candidates -b 2048 | |
288 | .Pp | |
289 | By default, the search for primes begins at a random point in the | |
290 | desired length range. | |
291 | This may be overridden using the | |
292 | .Fl S | |
293 | option, which specifies a different start point (in hex). | |
294 | .Pp | |
295 | Once a set of candidates have been generated, they must be tested for | |
296 | suitability. | |
297 | This may be performed using the | |
298 | .Fl T | |
299 | option. | |
300 | In this mode | |
301 | .Nm | |
302 | will read candidates from standard input (or a file specified using the | |
303 | .Fl f | |
304 | option). | |
305 | For example: | |
306 | .Pp | |
307 | .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates | |
308 | .Pp | |
309 | By default, each candidate will be subjected to 100 primality tests. | |
310 | This may be overridden using the | |
311 | .Fl a | |
312 | option. | |
313 | The DH generator value will be chosen automatically for the | |
314 | prime under consideration. | |
315 | If a specific generator is desired, it may be requested using the | |
316 | .Fl W | |
317 | option. | |
318 | Valid generator values are 2, 3 and 5. | |
319 | .Pp | |
320 | Screened DH groups may be installed in | |
321 | .Pa /etc/moduli . | |
322 | It is important that this file contains moduli of a range of bit lengths and | |
323 | that both ends of a connection share common moduli. | |
bf740959 | 324 | .Sh FILES |
325 | .Bl -tag -width Ds | |
bf740959 | 326 | .It Pa $HOME/.ssh/identity |
c0ecc314 | 327 | Contains the protocol version 1 RSA authentication identity of the user. |
4fe2af09 | 328 | This file should not be readable by anyone but the user. |
329 | It is possible to | |
bf740959 | 330 | specify a passphrase when generating the key; that passphrase will be |
4fe2af09 | 331 | used to encrypt the private part of this file using 3DES. |
332 | This file is not automatically accessed by | |
bf740959 | 333 | .Nm |
334 | but it is offered as the default file for the private key. | |
8a497b11 | 335 | .Xr ssh 1 |
1d1ffb87 | 336 | will read this file when a login attempt is made. |
bf740959 | 337 | .It Pa $HOME/.ssh/identity.pub |
c0ecc314 | 338 | Contains the protocol version 1 RSA public key for authentication. |
4fe2af09 | 339 | The contents of this file should be added to |
bf740959 | 340 | .Pa $HOME/.ssh/authorized_keys |
341 | on all machines | |
91789042 | 342 | where the user wishes to log in using RSA authentication. |
4fe2af09 | 343 | There is no need to keep the contents of this file secret. |
1d1ffb87 | 344 | .It Pa $HOME/.ssh/id_dsa |
c0ecc314 | 345 | Contains the protocol version 2 DSA authentication identity of the user. |
1d1ffb87 | 346 | This file should not be readable by anyone but the user. |
347 | It is possible to | |
348 | specify a passphrase when generating the key; that passphrase will be | |
349 | used to encrypt the private part of this file using 3DES. | |
350 | This file is not automatically accessed by | |
351 | .Nm | |
352 | but it is offered as the default file for the private key. | |
8a497b11 | 353 | .Xr ssh 1 |
1d1ffb87 | 354 | will read this file when a login attempt is made. |
355 | .It Pa $HOME/.ssh/id_dsa.pub | |
c0ecc314 | 356 | Contains the protocol version 2 DSA public key for authentication. |
357 | The contents of this file should be added to | |
96a7b0cc | 358 | .Pa $HOME/.ssh/authorized_keys |
c0ecc314 | 359 | on all machines |
91789042 | 360 | where the user wishes to log in using public key authentication. |
c0ecc314 | 361 | There is no need to keep the contents of this file secret. |
362 | .It Pa $HOME/.ssh/id_rsa | |
363 | Contains the protocol version 2 RSA authentication identity of the user. | |
364 | This file should not be readable by anyone but the user. | |
365 | It is possible to | |
366 | specify a passphrase when generating the key; that passphrase will be | |
367 | used to encrypt the private part of this file using 3DES. | |
368 | This file is not automatically accessed by | |
369 | .Nm | |
370 | but it is offered as the default file for the private key. | |
8a497b11 | 371 | .Xr ssh 1 |
c0ecc314 | 372 | will read this file when a login attempt is made. |
373 | .It Pa $HOME/.ssh/id_rsa.pub | |
374 | Contains the protocol version 2 RSA public key for authentication. | |
1d1ffb87 | 375 | The contents of this file should be added to |
96a7b0cc | 376 | .Pa $HOME/.ssh/authorized_keys |
1d1ffb87 | 377 | on all machines |
91789042 | 378 | where the user wishes to log in using public key authentication. |
1d1ffb87 | 379 | There is no need to keep the contents of this file secret. |
c35a6dc5 | 380 | .It Pa /etc/moduli |
381 | Contains Diffie-Hellman groups used for DH-GEX. | |
382 | The file format is described in | |
383 | .Xr moduli 5 . | |
089fbbd2 | 384 | .El |
bf740959 | 385 | .Sh SEE ALSO |
386 | .Xr ssh 1 , | |
387 | .Xr ssh-add 1 , | |
0c372277 | 388 | .Xr ssh-agent 1 , |
c35a6dc5 | 389 | .Xr moduli 5 , |
a5ef76f1 | 390 | .Xr sshd 8 |
5deceabb | 391 | .Rs |
7b518233 | 392 | .%A J. Galbraith |
393 | .%A R. Thayer | |
5deceabb | 394 | .%T "SECSH Public Key File Format" |
395 | .%N draft-ietf-secsh-publickeyfile-01.txt | |
396 | .%D March 2001 | |
397 | .%O work in progress material | |
398 | .Re | |
be193d89 | 399 | .Sh AUTHORS |
400 | OpenSSH is a derivative of the original and free | |
401 | ssh 1.2.12 release by Tatu Ylonen. | |
402 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, | |
403 | Theo de Raadt and Dug Song | |
404 | removed many bugs, re-added newer features and | |
405 | created OpenSSH. | |
406 | Markus Friedl contributed the support for SSH | |
407 | protocol versions 1.5 and 2.0. |