Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.28
1.1 deraadt 1: .\" -*- nroff -*-
2: .\"
3: .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4: .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: .\" All rights reserved
6: .\"
1.22 deraadt 7: .\" As far as I am concerned, the code I have written for this software
8: .\" can be used freely for any purpose. Any derived versions of this
9: .\" software must be clearly marked as such, and if the derived work is
10: .\" incompatible with the protocol description in the RFC file, it must be
11: .\" called by a name other than "ssh" or "Secure Shell".
12: .\"
13: .\"
14: .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
15: .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
16: .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
17: .\"
18: .\" Redistribution and use in source and binary forms, with or without
19: .\" modification, are permitted provided that the following conditions
20: .\" are met:
21: .\" 1. Redistributions of source code must retain the above copyright
22: .\" notice, this list of conditions and the following disclaimer.
23: .\" 2. Redistributions in binary form must reproduce the above copyright
24: .\" notice, this list of conditions and the following disclaimer in the
25: .\" documentation and/or other materials provided with the distribution.
1.1 deraadt 26: .\"
1.22 deraadt 27: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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36: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 deraadt 37: .\"
1.2 deraadt 38: .Dd September 25, 1999
39: .Dt SSH-KEYGEN 1
40: .Os
41: .Sh NAME
42: .Nm ssh-keygen
43: .Nd authentication key generation
44: .Sh SYNOPSIS
45: .Nm ssh-keygen
1.25 markus 46: .Op Fl q
1.2 deraadt 47: .Op Fl b Ar bits
1.25 markus 48: .Op Fl t Ar type
1.2 deraadt 49: .Op Fl N Ar new_passphrase
50: .Op Fl C Ar comment
1.20 markus 51: .Op Fl f Ar output_keyfile
1.2 deraadt 52: .Nm ssh-keygen
53: .Fl p
54: .Op Fl P Ar old_passphrase
55: .Op Fl N Ar new_passphrase
1.9 markus 56: .Op Fl f Ar keyfile
1.2 deraadt 57: .Nm ssh-keygen
1.16 deraadt 58: .Fl x
1.20 markus 59: .Op Fl f Ar input_keyfile
1.16 deraadt 60: .Nm ssh-keygen
61: .Fl X
1.20 markus 62: .Op Fl f Ar input_keyfile
1.16 deraadt 63: .Nm ssh-keygen
1.17 markus 64: .Fl y
1.20 markus 65: .Op Fl f Ar input_keyfile
1.17 markus 66: .Nm ssh-keygen
1.2 deraadt 67: .Fl c
68: .Op Fl P Ar passphrase
69: .Op Fl C Ar comment
1.9 markus 70: .Op Fl f Ar keyfile
71: .Nm ssh-keygen
72: .Fl l
1.20 markus 73: .Op Fl f Ar input_keyfile
1.13 aaron 74: .Sh DESCRIPTION
1.2 deraadt 75: .Nm
1.13 aaron 76: generates and manages authentication keys for
1.2 deraadt 77: .Xr ssh 1 .
1.15 deraadt 78: .Nm
79: defaults to generating an RSA key for use by protocols 1.3 and 1.5;
80: specifying the
1.25 markus 81: .Fl t
1.26 markus 82: option allows you to create a key for use by protocol 2.0.
1.15 deraadt 83: .Pp
1.2 deraadt 84: Normally each user wishing to use SSH
1.15 deraadt 85: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 86: key in
1.15 deraadt 87: .Pa $HOME/.ssh/identity
88: or
89: .Pa $HOME/.ssh/id_dsa .
90: Additionally, the system administrator may use this to generate host keys,
91: as seen in
92: .Pa /etc/rc .
1.2 deraadt 93: .Pp
1.1 deraadt 94: Normally this program generates the key and asks for a file in which
1.12 aaron 95: to store the private key.
96: The public key is stored in a file with the same name but
1.2 deraadt 97: .Dq .pub
1.12 aaron 98: appended.
99: The program also asks for a passphrase.
100: The passphrase may be empty to indicate no passphrase
1.26 markus 101: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 102: arbitrary length.
103: Good passphrases are 10-30 characters long and are
1.1 deraadt 104: not simple sentences or otherwise easily guessable (English
105: prose has only 1-2 bits of entropy per word, and provides very bad
1.12 aaron 106: passphrases).
107: The passphrase can be changed later by using the
1.2 deraadt 108: .Fl p
1.1 deraadt 109: option.
1.2 deraadt 110: .Pp
1.12 aaron 111: There is no way to recover a lost passphrase.
112: If the passphrase is
1.1 deraadt 113: lost or forgotten, you will have to generate a new key and copy the
114: corresponding public key to other machines.
1.2 deraadt 115: .Pp
1.15 deraadt 116: For RSA, there is also a comment field in the key file that is only for
1.12 aaron 117: convenience to the user to help identify the key.
118: The comment can tell what the key is for, or whatever is useful.
119: The comment is initialized to
1.2 deraadt 120: .Dq user@host
121: when the key is created, but can be changed using the
122: .Fl c
1.1 deraadt 123: option.
1.2 deraadt 124: .Pp
1.15 deraadt 125: After a key is generated, instructions below detail where the keys
126: should be placed to be activated.
127: .Pp
1.2 deraadt 128: The options are as follows:
129: .Bl -tag -width Ds
130: .It Fl b Ar bits
1.12 aaron 131: Specifies the number of bits in the key to create.
132: Minimum is 512 bits.
133: Generally 1024 bits is considered sufficient, and key sizes
134: above that no longer improve security but make things slower.
135: The default is 1024 bits.
1.2 deraadt 136: .It Fl c
1.1 deraadt 137: Requests changing the comment in the private and public key files.
138: The program will prompt for the file containing the private keys, for
139: passphrase if the key has one, and for the new comment.
1.9 markus 140: .It Fl f
141: Specifies the filename of the key file.
142: .It Fl l
143: Show fingerprint of specified private or public key file.
1.2 deraadt 144: .It Fl p
1.1 deraadt 145: Requests changing the passphrase of a private key file instead of
1.12 aaron 146: creating a new private key.
147: The program will prompt for the file
1.1 deraadt 148: containing the private key, for the old passphrase, and twice for the
149: new passphrase.
1.5 aaron 150: .It Fl q
151: Silence
152: .Nm ssh-keygen .
153: Used by
154: .Pa /etc/rc
155: when creating a new key.
1.25 markus 156: .It Fl t Ar type
157: Specifies the type of the key to create.
158: The possible values are
159: .Dq rsa1
160: for protocol version 1 and
161: .Dq rsa
162: or
163: .Dq dsa
164: for protocol version 2.
165: The default is
166: .Dq rsa .
1.2 deraadt 167: .It Fl C Ar comment
1.1 deraadt 168: Provides the new comment.
1.2 deraadt 169: .It Fl N Ar new_passphrase
1.1 deraadt 170: Provides the new passphrase.
1.2 deraadt 171: .It Fl P Ar passphrase
1.1 deraadt 172: Provides the (old) passphrase.
1.16 deraadt 173: .It Fl x
1.17 markus 174: This option will read a private
1.18 hugh 175: OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
1.16 deraadt 176: .It Fl X
1.23 markus 177: This option will read a unencrypted
178: SSH2-compatible private (or public) key file and
179: print an OpenSSH compatible private (or public) key to stdout.
1.17 markus 180: .It Fl y
181: This option will read a private
1.25 markus 182: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 183: .El
184: .Sh FILES
185: .Bl -tag -width Ds
186: .It Pa $HOME/.ssh/identity
1.12 aaron 187: Contains the RSA authentication identity of the user.
188: This file should not be readable by anyone but the user.
189: It is possible to
1.1 deraadt 190: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 191: used to encrypt the private part of this file using 3DES.
192: This file is not automatically accessed by
1.2 deraadt 193: .Nm
1.1 deraadt 194: but it is offered as the default file for the private key.
1.15 deraadt 195: .Xr sshd 8
196: will read this file when a login attempt is made.
1.2 deraadt 197: .It Pa $HOME/.ssh/identity.pub
1.12 aaron 198: Contains the public key for authentication.
199: The contents of this file should be added to
1.2 deraadt 200: .Pa $HOME/.ssh/authorized_keys
201: on all machines
1.12 aaron 202: where you wish to log in using RSA authentication.
1.15 deraadt 203: There is no need to keep the contents of this file secret.
204: .It Pa $HOME/.ssh/id_dsa
205: Contains the DSA authentication identity of the user.
206: This file should not be readable by anyone but the user.
207: It is possible to
208: specify a passphrase when generating the key; that passphrase will be
209: used to encrypt the private part of this file using 3DES.
210: This file is not automatically accessed by
211: .Nm
212: but it is offered as the default file for the private key.
213: .Xr sshd 8
214: will read this file when a login attempt is made.
215: .It Pa $HOME/.ssh/id_dsa.pub
216: Contains the public key for authentication.
217: The contents of this file should be added to
218: .Pa $HOME/.ssh/authorized_keys2
219: on all machines
1.25 markus 220: where you wish to log in using public key authentication.
1.12 aaron 221: There is no need to keep the contents of this file secret.
1.19 aaron 222: .El
1.24 aaron 223: .Sh AUTHORS
1.28 ! markus 224: OpenSSH is a derivative of the original and free
! 225: ssh 1.2.12 release by Tatu Ylonen.
! 226: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
! 227: Theo de Raadt and Dug Song
! 228: removed many bugs, re-added newer features and
! 229: created OpenSSH.
! 230: Markus Friedl contributed the support for SSH
! 231: protocol versions 1.5 and 2.0.
1.2 deraadt 232: .Sh SEE ALSO
233: .Xr ssh 1 ,
234: .Xr ssh-add 1 ,
1.8 ericj 235: .Xr ssh-agent 1 ,
1.4 deraadt 236: .Xr sshd 8 ,
237: .Xr ssl 8
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