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Ben Lindstrome5b3fb32001-02-10 23:56:35 +00001.\" $OpenBSD: ssh-keygen.1,v 1.30 2001/02/08 19:22:38 itojun Exp $
Ben Lindstrom36579d32001-01-29 07:39:26 +00002.\"
Damien Miller32aa1441999-10-29 09:15:49 +10003.\" -*- nroff -*-
4.\"
Damien Miller32aa1441999-10-29 09:15:49 +10005.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller32aa1441999-10-29 09:15:49 +10006.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7.\" All rights reserved
8.\"
Damien Millere4340be2000-09-16 13:29:08 +11009.\" 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".
Damien Miller32aa1441999-10-29 09:15:49 +100014.\"
Damien Millere4340be2000-09-16 13:29:08 +110015.\"
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.
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.
28.\"
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.
Damien Miller32aa1441999-10-29 09:15:49 +100039.\"
40.Dd September 25, 1999
41.Dt SSH-KEYGEN 1
42.Os
43.Sh NAME
44.Nm ssh-keygen
45.Nd authentication key generation
46.Sh SYNOPSIS
47.Nm ssh-keygen
Damien Miller0bc1bd82000-11-13 22:57:25 +110048.Op Fl q
Damien Miller32aa1441999-10-29 09:15:49 +100049.Op Fl b Ar bits
Damien Miller0bc1bd82000-11-13 22:57:25 +110050.Op Fl t Ar type
Damien Miller32aa1441999-10-29 09:15:49 +100051.Op Fl N Ar new_passphrase
52.Op Fl C Ar comment
Damien Miller1a425f32000-09-02 10:08:09 +110053.Op Fl f Ar output_keyfile
Damien Miller32aa1441999-10-29 09:15:49 +100054.Nm ssh-keygen
55.Fl p
56.Op Fl P Ar old_passphrase
57.Op Fl N Ar new_passphrase
Damien Miller10f6f6b1999-11-17 17:29:08 +110058.Op Fl f Ar keyfile
Damien Miller32aa1441999-10-29 09:15:49 +100059.Nm ssh-keygen
Damien Millere247cc42000-05-07 12:03:14 +100060.Fl x
Damien Miller1a425f32000-09-02 10:08:09 +110061.Op Fl f Ar input_keyfile
Damien Millere247cc42000-05-07 12:03:14 +100062.Nm ssh-keygen
63.Fl X
Damien Miller1a425f32000-09-02 10:08:09 +110064.Op Fl f Ar input_keyfile
Damien Millere247cc42000-05-07 12:03:14 +100065.Nm ssh-keygen
66.Fl y
Damien Miller1a425f32000-09-02 10:08:09 +110067.Op Fl f Ar input_keyfile
Damien Millere247cc42000-05-07 12:03:14 +100068.Nm ssh-keygen
Damien Miller32aa1441999-10-29 09:15:49 +100069.Fl c
70.Op Fl P Ar passphrase
71.Op Fl C Ar comment
Damien Miller10f6f6b1999-11-17 17:29:08 +110072.Op Fl f Ar keyfile
73.Nm ssh-keygen
74.Fl l
Damien Miller1a425f32000-09-02 10:08:09 +110075.Op Fl f Ar input_keyfile
Damien Miller22c77262000-04-13 12:26:34 +100076.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100077.Nm
Damien Miller22c77262000-04-13 12:26:34 +100078generates and manages authentication keys for
Damien Miller32aa1441999-10-29 09:15:49 +100079.Xr ssh 1 .
Damien Millere247cc42000-05-07 12:03:14 +100080.Nm
81defaults to generating an RSA key for use by protocols 1.3 and 1.5;
82specifying the
Damien Miller0bc1bd82000-11-13 22:57:25 +110083.Fl t
Ben Lindstrombf555ba2001-01-18 02:04:35 +000084option allows you to create a key for use by protocol 2.0.
Damien Millere247cc42000-05-07 12:03:14 +100085.Pp
Damien Miller32aa1441999-10-29 09:15:49 +100086Normally each user wishing to use SSH
Damien Millere247cc42000-05-07 12:03:14 +100087with RSA or DSA authentication runs this once to create the authentication
Damien Miller32aa1441999-10-29 09:15:49 +100088key in
Damien Millere247cc42000-05-07 12:03:14 +100089.Pa $HOME/.ssh/identity
90or
91.Pa $HOME/.ssh/id_dsa .
92Additionally, the system administrator may use this to generate host keys,
93as seen in
94.Pa /etc/rc .
Damien Miller32aa1441999-10-29 09:15:49 +100095.Pp
96Normally this program generates the key and asks for a file in which
Damien Miller450a7a12000-03-26 13:04:51 +100097to store the private key.
98The public key is stored in a file with the same name but
Damien Miller32aa1441999-10-29 09:15:49 +100099.Dq .pub
Damien Miller450a7a12000-03-26 13:04:51 +1000100appended.
101The program also asks for a passphrase.
102The passphrase may be empty to indicate no passphrase
Ben Lindstrombf555ba2001-01-18 02:04:35 +0000103(host keys must have an empty passphrase), or it may be a string of
Damien Miller450a7a12000-03-26 13:04:51 +1000104arbitrary length.
105Good passphrases are 10-30 characters long and are
Damien Miller32aa1441999-10-29 09:15:49 +1000106not simple sentences or otherwise easily guessable (English
107prose has only 1-2 bits of entropy per word, and provides very bad
Damien Miller450a7a12000-03-26 13:04:51 +1000108passphrases).
109The passphrase can be changed later by using the
Damien Miller32aa1441999-10-29 09:15:49 +1000110.Fl p
111option.
112.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000113There is no way to recover a lost passphrase.
114If the passphrase is
Damien Miller32aa1441999-10-29 09:15:49 +1000115lost or forgotten, you will have to generate a new key and copy the
116corresponding public key to other machines.
117.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000118For RSA, there is also a comment field in the key file that is only for
Damien Miller450a7a12000-03-26 13:04:51 +1000119convenience to the user to help identify the key.
120The comment can tell what the key is for, or whatever is useful.
121The comment is initialized to
Damien Miller32aa1441999-10-29 09:15:49 +1000122.Dq user@host
123when the key is created, but can be changed using the
124.Fl c
125option.
126.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000127After a key is generated, instructions below detail where the keys
128should be placed to be activated.
129.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000130The options are as follows:
131.Bl -tag -width Ds
132.It Fl b Ar bits
Damien Miller450a7a12000-03-26 13:04:51 +1000133Specifies the number of bits in the key to create.
134Minimum is 512 bits.
135Generally 1024 bits is considered sufficient, and key sizes
136above that no longer improve security but make things slower.
137The default is 1024 bits.
Damien Miller32aa1441999-10-29 09:15:49 +1000138.It Fl c
139Requests changing the comment in the private and public key files.
140The program will prompt for the file containing the private keys, for
141passphrase if the key has one, and for the new comment.
Damien Miller10f6f6b1999-11-17 17:29:08 +1100142.It Fl f
143Specifies the filename of the key file.
144.It Fl l
145Show fingerprint of specified private or public key file.
Damien Miller32aa1441999-10-29 09:15:49 +1000146.It Fl p
147Requests changing the passphrase of a private key file instead of
Damien Miller450a7a12000-03-26 13:04:51 +1000148creating a new private key.
149The program will prompt for the file
Damien Miller32aa1441999-10-29 09:15:49 +1000150containing the private key, for the old passphrase, and twice for the
151new passphrase.
152.It Fl q
153Silence
154.Nm ssh-keygen .
155Used by
156.Pa /etc/rc
157when creating a new key.
Damien Miller0bc1bd82000-11-13 22:57:25 +1100158.It Fl t Ar type
159Specifies the type of the key to create.
160The possible values are
161.Dq rsa1
162for protocol version 1 and
163.Dq rsa
164or
165.Dq dsa
166for protocol version 2.
167The default is
168.Dq rsa .
Damien Miller32aa1441999-10-29 09:15:49 +1000169.It Fl C Ar comment
170Provides the new comment.
171.It Fl N Ar new_passphrase
172Provides the new passphrase.
173.It Fl P Ar passphrase
174Provides the (old) passphrase.
Damien Millere247cc42000-05-07 12:03:14 +1000175.It Fl x
176This option will read a private
Damien Miller30c3d422000-05-09 11:02:59 +1000177OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
Damien Millere247cc42000-05-07 12:03:14 +1000178.It Fl X
Damien Miller874d77b2000-10-14 16:23:11 +1100179This option will read a unencrypted
180SSH2-compatible private (or public) key file and
181print an OpenSSH compatible private (or public) key to stdout.
Damien Millere247cc42000-05-07 12:03:14 +1000182.It Fl y
183This option will read a private
Damien Miller0bc1bd82000-11-13 22:57:25 +1100184OpenSSH format file and print an OpenSSH public key to stdout.
Damien Miller32aa1441999-10-29 09:15:49 +1000185.El
186.Sh FILES
187.Bl -tag -width Ds
Damien Miller32aa1441999-10-29 09:15:49 +1000188.It Pa $HOME/.ssh/identity
Damien Miller450a7a12000-03-26 13:04:51 +1000189Contains the RSA authentication identity of the user.
190This file should not be readable by anyone but the user.
191It is possible to
Damien Miller32aa1441999-10-29 09:15:49 +1000192specify a passphrase when generating the key; that passphrase will be
Damien Miller450a7a12000-03-26 13:04:51 +1000193used to encrypt the private part of this file using 3DES.
194This file is not automatically accessed by
Damien Miller32aa1441999-10-29 09:15:49 +1000195.Nm
196but it is offered as the default file for the private key.
Damien Millere247cc42000-05-07 12:03:14 +1000197.Xr sshd 8
198will read this file when a login attempt is made.
Damien Miller32aa1441999-10-29 09:15:49 +1000199.It Pa $HOME/.ssh/identity.pub
Damien Miller450a7a12000-03-26 13:04:51 +1000200Contains the public key for authentication.
201The contents of this file should be added to
Damien Miller32aa1441999-10-29 09:15:49 +1000202.Pa $HOME/.ssh/authorized_keys
203on all machines
Damien Miller450a7a12000-03-26 13:04:51 +1000204where you wish to log in using RSA authentication.
205There is no need to keep the contents of this file secret.
Damien Millere247cc42000-05-07 12:03:14 +1000206.It Pa $HOME/.ssh/id_dsa
207Contains the DSA authentication identity of the user.
208This file should not be readable by anyone but the user.
209It is possible to
210specify a passphrase when generating the key; that passphrase will be
211used to encrypt the private part of this file using 3DES.
212This file is not automatically accessed by
213.Nm
214but it is offered as the default file for the private key.
215.Xr sshd 8
216will read this file when a login attempt is made.
217.It Pa $HOME/.ssh/id_dsa.pub
218Contains the public key for authentication.
219The contents of this file should be added to
220.Pa $HOME/.ssh/authorized_keys2
221on all machines
Damien Miller0bc1bd82000-11-13 22:57:25 +1100222where you wish to log in using public key authentication.
Damien Millere247cc42000-05-07 12:03:14 +1000223There is no need to keep the contents of this file secret.
Damien Miller37023962000-07-11 17:31:38 +1000224.El
Damien Miller0bc1bd82000-11-13 22:57:25 +1100225.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +0000226OpenSSH is a derivative of the original and free
227ssh 1.2.12 release by Tatu Ylonen.
228Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
229Theo de Raadt and Dug Song
230removed many bugs, re-added newer features and
231created OpenSSH.
232Markus Friedl contributed the support for SSH
233protocol versions 1.5 and 2.0.
Damien Miller32aa1441999-10-29 09:15:49 +1000234.Sh SEE ALSO
235.Xr ssh 1 ,
236.Xr ssh-add 1 ,
Damien Miller2e8b1c81999-11-15 23:33:56 +1100237.Xr ssh-agent 1 ,
Ben Lindstrom77788dc2001-02-10 23:10:33 +0000238.Xr sshd 8