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Ben Lindstrom2a097a42001-06-09 01:13:40 +00001.\" $OpenBSD: ssh-keygen.1,v 1.42 2001/06/03 19:36:44 markus 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.\"
Ben Lindstrom92a2e382001-03-05 06:59:27 +000016.\" 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.
Damien Millere4340be2000-09-16 13:29:08 +110019.\"
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
Ben Lindstrom5a707822001-04-22 17:15:46 +000045.Nd authentication key generation, management and conversion
Damien Miller32aa1441999-10-29 09:15:49 +100046.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
Ben Lindstrom5a707822001-04-22 17:15:46 +000060.Fl i
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
Ben Lindstrom5a707822001-04-22 17:15:46 +000063.Fl e
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
Ben Lindstrom8fd372b2001-03-12 03:02:17 +000075.Op Fl f Ar input_keyfile
76.Nm ssh-keygen
77.Fl B
Damien Miller1a425f32000-09-02 10:08:09 +110078.Op Fl f Ar input_keyfile
Damien Miller22c77262000-04-13 12:26:34 +100079.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100080.Nm
Ben Lindstrom5a707822001-04-22 17:15:46 +000081generates, manages and converts authentication keys for
Damien Miller32aa1441999-10-29 09:15:49 +100082.Xr ssh 1 .
Damien Millere247cc42000-05-07 12:03:14 +100083.Nm
Ben Lindstromc65e6a02001-04-23 13:02:16 +000084defaults to generating a RSA1 key for use by SSH protocol version 1.
Damien Millere247cc42000-05-07 12:03:14 +100085specifying the
Damien Miller0bc1bd82000-11-13 22:57:25 +110086.Fl t
Ben Lindstromc65e6a02001-04-23 13:02:16 +000087option allows you to create a key for use by SSH protocol version 2.
Damien Millere247cc42000-05-07 12:03:14 +100088.Pp
Damien Miller32aa1441999-10-29 09:15:49 +100089Normally each user wishing to use SSH
Damien Millere247cc42000-05-07 12:03:14 +100090with RSA or DSA authentication runs this once to create the authentication
Damien Miller32aa1441999-10-29 09:15:49 +100091key in
Ben Lindstrom18a82ac2001-04-11 15:59:35 +000092.Pa $HOME/.ssh/identity ,
93.Pa $HOME/.ssh/id_dsa
Damien Millere247cc42000-05-07 12:03:14 +100094or
Ben Lindstrom18a82ac2001-04-11 15:59:35 +000095.Pa $HOME/.ssh/id_rsa .
Damien Millere247cc42000-05-07 12:03:14 +100096Additionally, the system administrator may use this to generate host keys,
97as seen in
98.Pa /etc/rc .
Damien Miller32aa1441999-10-29 09:15:49 +100099.Pp
100Normally this program generates the key and asks for a file in which
Damien Miller450a7a12000-03-26 13:04:51 +1000101to store the private key.
102The public key is stored in a file with the same name but
Damien Miller32aa1441999-10-29 09:15:49 +1000103.Dq .pub
Damien Miller450a7a12000-03-26 13:04:51 +1000104appended.
105The program also asks for a passphrase.
106The passphrase may be empty to indicate no passphrase
Ben Lindstrombf555ba2001-01-18 02:04:35 +0000107(host keys must have an empty passphrase), or it may be a string of
Damien Miller450a7a12000-03-26 13:04:51 +1000108arbitrary length.
109Good passphrases are 10-30 characters long and are
Damien Miller32aa1441999-10-29 09:15:49 +1000110not simple sentences or otherwise easily guessable (English
Ben Lindstrom2a097a42001-06-09 01:13:40 +0000111prose has only 1-2 bits of entropy per character, and provides very bad
Damien Miller450a7a12000-03-26 13:04:51 +1000112passphrases).
113The passphrase can be changed later by using the
Damien Miller32aa1441999-10-29 09:15:49 +1000114.Fl p
115option.
116.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000117There is no way to recover a lost passphrase.
118If the passphrase is
Damien Miller32aa1441999-10-29 09:15:49 +1000119lost or forgotten, you will have to generate a new key and copy the
120corresponding public key to other machines.
121.Pp
Ben Lindstrom5a707822001-04-22 17:15:46 +0000122For RSA1 keys,
123there is also a comment field in the key file that is only for
Damien Miller450a7a12000-03-26 13:04:51 +1000124convenience to the user to help identify the key.
125The comment can tell what the key is for, or whatever is useful.
126The comment is initialized to
Damien Miller32aa1441999-10-29 09:15:49 +1000127.Dq user@host
128when the key is created, but can be changed using the
129.Fl c
130option.
131.Pp
Damien Millere247cc42000-05-07 12:03:14 +1000132After a key is generated, instructions below detail where the keys
133should be placed to be activated.
134.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000135The options are as follows:
136.Bl -tag -width Ds
137.It Fl b Ar bits
Damien Miller450a7a12000-03-26 13:04:51 +1000138Specifies the number of bits in the key to create.
139Minimum is 512 bits.
140Generally 1024 bits is considered sufficient, and key sizes
141above that no longer improve security but make things slower.
142The default is 1024 bits.
Damien Miller32aa1441999-10-29 09:15:49 +1000143.It Fl c
144Requests changing the comment in the private and public key files.
145The program will prompt for the file containing the private keys, for
Ben Lindstromaafff9c2001-05-06 03:01:02 +0000146the passphrase if the key has one, and for the new comment.
Ben Lindstrom5a707822001-04-22 17:15:46 +0000147.It Fl e
Ben Lindstrom46c264f2001-04-24 16:56:58 +0000148This option will read a private or public OpenSSH key file and
149print the key in a
Ben Lindstrom5a707822001-04-22 17:15:46 +0000150.Sq SECSH Public Key File Format
151to stdout.
152This option allows exporting keys for use by several commercial
153SSH implementations.
Damien Miller10f6f6b1999-11-17 17:29:08 +1100154.It Fl f
155Specifies the filename of the key file.
Ben Lindstrom5a707822001-04-22 17:15:46 +0000156.It Fl i
157This option will read an unencrypted private (or public) key file
158in SSH2-compatible format and print an OpenSSH compatible private
159(or public) key to stdout.
160.Nm
Ben Lindstrom2857d9c2001-04-22 17:19:46 +0000161also reads the
Ben Lindstrom5a707822001-04-22 17:15:46 +0000162.Sq SECSH Public Key File Format .
163This option allows importing keys from several commercial
164SSH implementations.
Damien Miller10f6f6b1999-11-17 17:29:08 +1100165.It Fl l
166Show fingerprint of specified private or public key file.
Damien Miller32aa1441999-10-29 09:15:49 +1000167.It Fl p
168Requests changing the passphrase of a private key file instead of
Damien Miller450a7a12000-03-26 13:04:51 +1000169creating a new private key.
170The program will prompt for the file
Damien Miller32aa1441999-10-29 09:15:49 +1000171containing the private key, for the old passphrase, and twice for the
172new passphrase.
173.It Fl q
174Silence
175.Nm ssh-keygen .
176Used by
177.Pa /etc/rc
178when creating a new key.
Ben Lindstrom5a707822001-04-22 17:15:46 +0000179.It Fl y
180This option will read a private
181OpenSSH format file and print an OpenSSH public key to stdout.
Damien Miller0bc1bd82000-11-13 22:57:25 +1100182.It Fl t Ar type
183Specifies the type of the key to create.
184The possible values are
185.Dq rsa1
186for protocol version 1 and
187.Dq rsa
188or
189.Dq dsa
190for protocol version 2.
191The default is
Ben Lindstromb7c92322001-03-05 05:10:52 +0000192.Dq rsa1 .
Ben Lindstrom8fd372b2001-03-12 03:02:17 +0000193.It Fl B
194Show the bubblebabble digest of specified private or public key file.
Damien Miller32aa1441999-10-29 09:15:49 +1000195.It Fl C Ar comment
196Provides the new comment.
197.It Fl N Ar new_passphrase
198Provides the new passphrase.
199.It Fl P Ar passphrase
200Provides the (old) passphrase.
201.El
202.Sh FILES
203.Bl -tag -width Ds
Damien Miller32aa1441999-10-29 09:15:49 +1000204.It Pa $HOME/.ssh/identity
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000205Contains the protocol version 1 RSA authentication identity of the user.
Damien Miller450a7a12000-03-26 13:04:51 +1000206This file should not be readable by anyone but the user.
207It is possible to
Damien Miller32aa1441999-10-29 09:15:49 +1000208specify a passphrase when generating the key; that passphrase will be
Damien Miller450a7a12000-03-26 13:04:51 +1000209used to encrypt the private part of this file using 3DES.
210This file is not automatically accessed by
Damien Miller32aa1441999-10-29 09:15:49 +1000211.Nm
212but it is offered as the default file for the private key.
Damien Millere247cc42000-05-07 12:03:14 +1000213.Xr sshd 8
214will read this file when a login attempt is made.
Damien Miller32aa1441999-10-29 09:15:49 +1000215.It Pa $HOME/.ssh/identity.pub
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000216Contains the protocol version 1 RSA public key for authentication.
Damien Miller450a7a12000-03-26 13:04:51 +1000217The contents of this file should be added to
Damien Miller32aa1441999-10-29 09:15:49 +1000218.Pa $HOME/.ssh/authorized_keys
219on all machines
Damien Miller450a7a12000-03-26 13:04:51 +1000220where you wish to log in using RSA authentication.
221There is no need to keep the contents of this file secret.
Damien Millere247cc42000-05-07 12:03:14 +1000222.It Pa $HOME/.ssh/id_dsa
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000223Contains the protocol version 2 DSA authentication identity of the user.
Damien Millere247cc42000-05-07 12:03:14 +1000224This file should not be readable by anyone but the user.
225It is possible to
226specify a passphrase when generating the key; that passphrase will be
227used to encrypt the private part of this file using 3DES.
228This file is not automatically accessed by
229.Nm
230but it is offered as the default file for the private key.
231.Xr sshd 8
232will read this file when a login attempt is made.
233.It Pa $HOME/.ssh/id_dsa.pub
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000234Contains the protocol version 2 DSA public key for authentication.
235The contents of this file should be added to
236.Pa $HOME/.ssh/authorized_keys2
237on all machines
238where you wish to log in using public key authentication.
239There is no need to keep the contents of this file secret.
240.It Pa $HOME/.ssh/id_rsa
241Contains the protocol version 2 RSA authentication identity of the user.
242This file should not be readable by anyone but the user.
243It is possible to
244specify a passphrase when generating the key; that passphrase will be
245used to encrypt the private part of this file using 3DES.
246This file is not automatically accessed by
247.Nm
248but it is offered as the default file for the private key.
249.Xr sshd 8
250will read this file when a login attempt is made.
251.It Pa $HOME/.ssh/id_rsa.pub
252Contains the protocol version 2 RSA public key for authentication.
Damien Millere247cc42000-05-07 12:03:14 +1000253The contents of this file should be added to
254.Pa $HOME/.ssh/authorized_keys2
255on all machines
Damien Miller0bc1bd82000-11-13 22:57:25 +1100256where you wish to log in using public key authentication.
Damien Millere247cc42000-05-07 12:03:14 +1000257There is no need to keep the contents of this file secret.
Damien Miller37023962000-07-11 17:31:38 +1000258.El
Damien Miller0bc1bd82000-11-13 22:57:25 +1100259.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +0000260OpenSSH is a derivative of the original and free
261ssh 1.2.12 release by Tatu Ylonen.
262Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
263Theo de Raadt and Dug Song
264removed many bugs, re-added newer features and
265created OpenSSH.
266Markus Friedl contributed the support for SSH
267protocol versions 1.5 and 2.0.
Damien Miller32aa1441999-10-29 09:15:49 +1000268.Sh SEE ALSO
269.Xr ssh 1 ,
270.Xr ssh-add 1 ,
Damien Miller2e8b1c81999-11-15 23:33:56 +1100271.Xr ssh-agent 1 ,
Ben Lindstrom77788dc2001-02-10 23:10:33 +0000272.Xr sshd 8
Ben Lindstrom5a707822001-04-22 17:15:46 +0000273.Rs
274.%A J. Galbraith
275.%A R. Thayer
276.%T "SECSH Public Key File Format"
277.%N draft-ietf-secsh-publickeyfile-01.txt
278.%D March 2001
279.%O work in progress material
280.Re