1 .\" $OpenBSD: ssh-keygen.1,v 1.60 2003/07/28 09:49:56 djm Exp $
5 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
6 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7 .\" All rights reserved
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".
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.
20 .\" Redistribution and use in source and binary forms, with or without
21 .\" modification, are permitted provided that the following conditions
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.
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
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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.
40 .Dd September 25, 1999
45 .Nd authentication key generation, management and conversion
52 .Op Fl N Ar new_passphrase
54 .Op Fl f Ar output_keyfile
58 .Op Fl P Ar old_passphrase
59 .Op Fl N Ar new_passphrase
63 .Op Fl f Ar input_keyfile
66 .Op Fl f Ar input_keyfile
69 .Op Fl f Ar input_keyfile
72 .Op Fl P Ar passphrase
77 .Op Fl f Ar input_keyfile
80 .Op Fl f Ar input_keyfile
85 .Op Fl f Ar input_keyfile
88 .Op Fl f Ar input_keyfile
94 .Op Fl S Ar start_point
98 .Op Fl a Ar num_trials
102 generates, manages and converts authentication keys for
105 can create RSA keys for use by SSH protocol version 1 and RSA or DSA
106 keys for use by SSH protocol version 2.
107 The type of key to be generated is specified with the
112 is also used to generate groups for use in Diffie-Hellman group
115 .Sx MODULI GENERATION
118 Normally each user wishing to use SSH
119 with RSA or DSA authentication runs this once to create the authentication
121 .Pa $HOME/.ssh/identity ,
122 .Pa $HOME/.ssh/id_dsa
124 .Pa $HOME/.ssh/id_rsa .
125 Additionally, the system administrator may use this to generate host keys,
129 Normally this program generates the key and asks for a file in which
130 to store the private key.
131 The public key is stored in a file with the same name but
134 The program also asks for a passphrase.
135 The passphrase may be empty to indicate no passphrase
136 (host keys must have an empty passphrase), or it may be a string of
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
141 Good passphrases are 10-30 characters long, are
142 not simple sentences or otherwise easily guessable (English
143 prose has only 1-2 bits of entropy per character, and provides very bad
144 passphrases), and contain a mix of upper and lowercase letters,
145 numbers, and non-alphanumeric characters.
146 The passphrase can be changed later by using the
150 There is no way to recover a lost passphrase.
152 lost or forgotten, a new key must be generated and copied to the
153 corresponding public key to other machines.
156 there is also a comment field in the key file that is only for
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
161 when the key is created, but can be changed using the
165 After a key is generated, instructions below detail where the keys
166 should be placed to be activated.
168 The options are as follows:
171 Specifies the number of primality tests to perform when screening DH-GEX
176 Specifies the number of bits in the key to create.
178 Generally, 1024 bits is considered sufficient.
179 The default is 1024 bits.
181 Requests changing the comment in the private and public key files.
182 This operation is only supported for RSA1 keys.
183 The program will prompt for the file containing the private keys, for
184 the passphrase if the key has one, and for the new comment.
186 This option will read a private or public OpenSSH key file and
188 .Sq SECSH Public Key File Format
190 This option allows exporting keys for use by several commercial
193 Use generic DNS resource record format.
195 Specifies the filename of the key file.
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.
202 .Sq SECSH Public Key File Format .
203 This option allows importing keys from several commercial
206 Show fingerprint of specified public key file.
207 Private RSA1 keys are also supported.
210 tries to find the matching public key file and prints its fingerprint.
212 Requests changing the passphrase of a private key file instead of
213 creating a new private key.
214 The program will prompt for the file
215 containing the private key, for the old passphrase, and twice for the
222 when creating a new key.
224 This option will read a private
225 OpenSSH format file and print an OpenSSH public key to stdout.
227 Specifies the type of the key to create.
228 The possible values are
230 for protocol version 1 and
234 for protocol version 2.
236 Show the bubblebabble digest of specified private or public key file.
238 Provides the new comment.
240 Download the RSA public key stored in the smartcard in
242 .It Fl G Ar output_file
243 Generate candidate primes for DH-GEX.
244 These primes must be screened for
249 Specify the amount of memory to use (in megabytes) when generating
250 candidate moduli for DH-GEX.
251 .It Fl N Ar new_passphrase
252 Provides the new passphrase.
253 .It Fl P Ar passphrase
254 Provides the (old) passphrase.
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
261 .It Fl W Ar generator
262 Specify desired generator when testing candidate moduli for DH-GEX.
264 Upload an existing RSA private key into the smartcard in
267 Print DNS resource record with the specified
270 .Sh MODULI GENERATION
272 may be used to generate groups for the Diffie-Hellman Group Exchange
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
279 Generation of primes is performed using the
282 The desired length of the primes may be specified by the
287 .Dl ssh-keygen -G moduli-2048.candidates -b 2048
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
293 option, which specifies a different start point (in hex).
295 Once a set of candidates have been generated, they must be tested for
297 This may be performed using the
302 will read candidates from standard input (or a file specified using the
307 .Dl ssh-keygen -T moduli-2048 -f moduli-2048.candidates
309 By default, each candidate will be subjected to 100 primality tests.
310 This may be overridden using the
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
318 Valid generator values are 2, 3 and 5.
320 Screened DH groups may be installed in
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.
326 .It Pa $HOME/.ssh/identity
327 Contains the protocol version 1 RSA authentication identity of the user.
328 This file should not be readable by anyone but the user.
330 specify a passphrase when generating the key; that passphrase will be
331 used to encrypt the private part of this file using 3DES.
332 This file is not automatically accessed by
334 but it is offered as the default file for the private key.
336 will read this file when a login attempt is made.
337 .It Pa $HOME/.ssh/identity.pub
338 Contains the protocol version 1 RSA public key for authentication.
339 The contents of this file should be added to
340 .Pa $HOME/.ssh/authorized_keys
342 where the user wishes to log in using RSA authentication.
343 There is no need to keep the contents of this file secret.
344 .It Pa $HOME/.ssh/id_dsa
345 Contains the protocol version 2 DSA authentication identity of the user.
346 This file should not be readable by anyone but the user.
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
352 but it is offered as the default file for the private key.
354 will read this file when a login attempt is made.
355 .It Pa $HOME/.ssh/id_dsa.pub
356 Contains the protocol version 2 DSA public key for authentication.
357 The contents of this file should be added to
358 .Pa $HOME/.ssh/authorized_keys
360 where the user wishes to log in using public key authentication.
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.
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
370 but it is offered as the default file for the private key.
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.
375 The contents of this file should be added to
376 .Pa $HOME/.ssh/authorized_keys
378 where the user wishes to log in using public key authentication.
379 There is no need to keep the contents of this file secret.
381 Contains Diffie-Hellman groups used for DH-GEX.
382 The file format is described in
394 .%T "SECSH Public Key File Format"
395 .%N draft-ietf-secsh-publickeyfile-01.txt
397 .%O work in progress material
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
406 Markus Friedl contributed the support for SSH
407 protocol versions 1.5 and 2.0.