1 .\" $OpenBSD: ssh-keygen.1,v 1.51 2001/11/21 18:49:14 stevesk 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
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.
40 .Dd September 25, 1999
45 .Nd authentication key generation, management and conversion
51 .Op Fl N Ar new_passphrase
53 .Op Fl f Ar output_keyfile
56 .Op Fl P Ar old_passphrase
57 .Op Fl N Ar new_passphrase
61 .Op Fl f Ar input_keyfile
64 .Op Fl f Ar input_keyfile
67 .Op Fl f Ar input_keyfile
70 .Op Fl P Ar passphrase
75 .Op Fl f Ar input_keyfile
78 .Op Fl f Ar input_keyfile
83 .Op Fl f Ar input_keyfile
86 generates, manages and converts authentication keys for
89 defaults to generating a RSA1 key for use by SSH protocol version 1.
92 option instead creates a key for use by SSH protocol version 2.
94 Normally each user wishing to use SSH
95 with RSA or DSA authentication runs this once to create the authentication
97 .Pa $HOME/.ssh/identity ,
100 .Pa $HOME/.ssh/id_rsa .
101 Additionally, the system administrator may use this to generate host keys,
105 Normally this program generates the key and asks for a file in which
106 to store the private key.
107 The public key is stored in a file with the same name but
110 The program also asks for a passphrase.
111 The passphrase may be empty to indicate no passphrase
112 (host keys must have an empty passphrase), or it may be a string of
114 A passphrase is similar to a password, except it can be a phrase with a
115 series of words, punctuation, numbers, whitespace, or any string of
117 Good passphrases are 10-30 characters long, are
118 not simple sentences or otherwise easily guessable (English
119 prose has only 1-2 bits of entropy per character, and provides very bad
120 passphrases), and contain a mix of upper and lowercase letters,
121 numbers, and non-alphanumeric characters.
122 The passphrase can be changed later by using the
126 There is no way to recover a lost passphrase.
128 lost or forgotten, a new key must be generated and copied to the
129 corresponding public key to other machines.
132 there is also a comment field in the key file that is only for
133 convenience to the user to help identify the key.
134 The comment can tell what the key is for, or whatever is useful.
135 The comment is initialized to
137 when the key is created, but can be changed using the
141 After a key is generated, instructions below detail where the keys
142 should be placed to be activated.
144 The options are as follows:
147 Specifies the number of bits in the key to create.
149 Generally 1024 bits is considered sufficient, and key sizes
150 above that no longer improve security but make things slower.
151 The default is 1024 bits.
153 Requests changing the comment in the private and public key files.
154 This operation is only supported for RSA1 keys.
155 The program will prompt for the file containing the private keys, for
156 the passphrase if the key has one, and for the new comment.
158 This option will read a private or public OpenSSH key file and
160 .Sq SECSH Public Key File Format
162 This option allows exporting keys for use by several commercial
165 Specifies the filename of the key file.
167 This option will read an unencrypted private (or public) key file
168 in SSH2-compatible format and print an OpenSSH compatible private
169 (or public) key to stdout.
172 .Sq SECSH Public Key File Format .
173 This option allows importing keys from several commercial
176 Show fingerprint of specified public key file.
177 Private RSA1 keys are also supported.
180 tries to find the matching public key file and prints its fingerprint.
182 Requests changing the passphrase of a private key file instead of
183 creating a new private key.
184 The program will prompt for the file
185 containing the private key, for the old passphrase, and twice for the
192 when creating a new key.
194 This option will read a private
195 OpenSSH format file and print an OpenSSH public key to stdout.
197 Specifies the type of the key to create.
198 The possible values are
200 for protocol version 1 and
204 for protocol version 2.
208 Show the bubblebabble digest of specified private or public key file.
210 Provides the new comment.
212 Download the RSA public key stored in the smartcard in
214 .It Fl N Ar new_passphrase
215 Provides the new passphrase.
216 .It Fl P Ar passphrase
217 Provides the (old) passphrase.
219 Upload an existing RSA private key into the smartcard in
224 .It Pa $HOME/.ssh/identity
225 Contains the protocol version 1 RSA authentication identity of the user.
226 This file should not be readable by anyone but the user.
228 specify a passphrase when generating the key; that passphrase will be
229 used to encrypt the private part of this file using 3DES.
230 This file is not automatically accessed by
232 but it is offered as the default file for the private key.
234 will read this file when a login attempt is made.
235 .It Pa $HOME/.ssh/identity.pub
236 Contains the protocol version 1 RSA public key for authentication.
237 The contents of this file should be added to
238 .Pa $HOME/.ssh/authorized_keys
240 where the user wishes to log in using RSA authentication.
241 There is no need to keep the contents of this file secret.
242 .It Pa $HOME/.ssh/id_dsa
243 Contains the protocol version 2 DSA authentication identity of the user.
244 This file should not be readable by anyone but the user.
246 specify a passphrase when generating the key; that passphrase will be
247 used to encrypt the private part of this file using 3DES.
248 This file is not automatically accessed by
250 but it is offered as the default file for the private key.
252 will read this file when a login attempt is made.
253 .It Pa $HOME/.ssh/id_dsa.pub
254 Contains the protocol version 2 DSA public key for authentication.
255 The contents of this file should be added to
256 .Pa $HOME/.ssh/authorized_keys
258 where the user wishes to log in using public key authentication.
259 There is no need to keep the contents of this file secret.
260 .It Pa $HOME/.ssh/id_rsa
261 Contains the protocol version 2 RSA authentication identity of the user.
262 This file should not be readable by anyone but the user.
264 specify a passphrase when generating the key; that passphrase will be
265 used to encrypt the private part of this file using 3DES.
266 This file is not automatically accessed by
268 but it is offered as the default file for the private key.
270 will read this file when a login attempt is made.
271 .It Pa $HOME/.ssh/id_rsa.pub
272 Contains the protocol version 2 RSA public key for authentication.
273 The contents of this file should be added to
274 .Pa $HOME/.ssh/authorized_keys
276 where the user wishes to log in using public key authentication.
277 There is no need to keep the contents of this file secret.
280 OpenSSH is a derivative of the original and free
281 ssh 1.2.12 release by Tatu Ylonen.
282 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
283 Theo de Raadt and Dug Song
284 removed many bugs, re-added newer features and
286 Markus Friedl contributed the support for SSH
287 protocol versions 1.5 and 2.0.
296 .%T "SECSH Public Key File Format"
297 .%N draft-ietf-secsh-publickeyfile-01.txt
299 .%O work in progress material