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bf740959 | 1 | .\" -*- nroff -*- |
2 | .\" | |
3 | .\" ssh-keygen.1 | |
4 | .\" | |
5 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | .\" | |
7 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | .\" All rights reserved | |
9 | .\" | |
10 | .\" Created: Sat Apr 22 23:55:14 1995 ylo | |
11 | .\" | |
12 | .\" $Id$ | |
13 | .\" | |
14 | .Dd September 25, 1999 | |
15 | .Dt SSH-KEYGEN 1 | |
16 | .Os | |
17 | .Sh NAME | |
18 | .Nm ssh-keygen | |
19 | .Nd authentication key generation | |
20 | .Sh SYNOPSIS | |
21 | .Nm ssh-keygen | |
22 | .Op Fl q | |
23 | .Op Fl b Ar bits | |
24 | .Op Fl N Ar new_passphrase | |
25 | .Op Fl C Ar comment | |
f095fcc7 | 26 | .Op Fl f Ar keyfile |
bf740959 | 27 | .Nm ssh-keygen |
28 | .Fl p | |
29 | .Op Fl P Ar old_passphrase | |
30 | .Op Fl N Ar new_passphrase | |
f095fcc7 | 31 | .Op Fl f Ar keyfile |
bf740959 | 32 | .Nm ssh-keygen |
33 | .Fl c | |
34 | .Op Fl P Ar passphrase | |
35 | .Op Fl C Ar comment | |
f095fcc7 | 36 | .Op Fl f Ar keyfile |
37 | .Nm ssh-keygen | |
38 | .Fl l | |
39 | .Op Fl f Ar keyfile | |
a306f2dd | 40 | .Nm ssh-keygen |
41 | .Fl R | |
f54651ce | 42 | .Sh DESCRIPTION |
bf740959 | 43 | .Nm |
f54651ce | 44 | generates and manages authentication keys for |
bf740959 | 45 | .Xr ssh 1 . |
46 | Normally each user wishing to use SSH | |
47 | with RSA authentication runs this once to create the authentication | |
48 | key in | |
49 | .Pa $HOME/.ssh/identity . | |
50 | Additionally, the system administrator may use this to generate host keys. | |
51 | .Pp | |
52 | Normally this program generates the key and asks for a file in which | |
4fe2af09 | 53 | to store the private key. |
54 | The public key is stored in a file with the same name but | |
bf740959 | 55 | .Dq .pub |
4fe2af09 | 56 | appended. |
57 | The program also asks for a passphrase. | |
58 | The passphrase may be empty to indicate no passphrase | |
bf740959 | 59 | (host keys must have empty passphrase), or it may be a string of |
4fe2af09 | 60 | arbitrary length. |
61 | Good passphrases are 10-30 characters long and are | |
bf740959 | 62 | not simple sentences or otherwise easily guessable (English |
63 | prose has only 1-2 bits of entropy per word, and provides very bad | |
4fe2af09 | 64 | passphrases). |
65 | The passphrase can be changed later by using the | |
bf740959 | 66 | .Fl p |
67 | option. | |
68 | .Pp | |
4fe2af09 | 69 | There is no way to recover a lost passphrase. |
70 | If the passphrase is | |
bf740959 | 71 | lost or forgotten, you will have to generate a new key and copy the |
72 | corresponding public key to other machines. | |
73 | .Pp | |
74 | There is also a comment field in the key file that is only for | |
4fe2af09 | 75 | convenience to the user to help identify the key. |
76 | The comment can tell what the key is for, or whatever is useful. | |
77 | The comment is initialized to | |
bf740959 | 78 | .Dq user@host |
79 | when the key is created, but can be changed using the | |
80 | .Fl c | |
81 | option. | |
82 | .Pp | |
83 | The options are as follows: | |
84 | .Bl -tag -width Ds | |
85 | .It Fl b Ar bits | |
4fe2af09 | 86 | Specifies the number of bits in the key to create. |
87 | Minimum is 512 bits. | |
88 | Generally 1024 bits is considered sufficient, and key sizes | |
89 | above that no longer improve security but make things slower. | |
90 | The default is 1024 bits. | |
bf740959 | 91 | .It Fl c |
92 | Requests changing the comment in the private and public key files. | |
93 | The program will prompt for the file containing the private keys, for | |
94 | passphrase if the key has one, and for the new comment. | |
f095fcc7 | 95 | .It Fl f |
96 | Specifies the filename of the key file. | |
97 | .It Fl l | |
98 | Show fingerprint of specified private or public key file. | |
bf740959 | 99 | .It Fl p |
100 | Requests changing the passphrase of a private key file instead of | |
4fe2af09 | 101 | creating a new private key. |
102 | The program will prompt for the file | |
bf740959 | 103 | containing the private key, for the old passphrase, and twice for the |
104 | new passphrase. | |
105 | .It Fl q | |
106 | Silence | |
107 | .Nm ssh-keygen . | |
108 | Used by | |
109 | .Pa /etc/rc | |
110 | when creating a new key. | |
111 | .It Fl C Ar comment | |
112 | Provides the new comment. | |
113 | .It Fl N Ar new_passphrase | |
114 | Provides the new passphrase. | |
115 | .It Fl P Ar passphrase | |
116 | Provides the (old) passphrase. | |
a306f2dd | 117 | .It Fl R |
118 | If RSA support is functional, immediately exits with code 0. If RSA | |
119 | support is not functional, exits with code 1. This flag will be | |
120 | removed once the RSA patent expires. | |
bf740959 | 121 | .El |
122 | .Sh FILES | |
123 | .Bl -tag -width Ds | |
bf740959 | 124 | .It Pa $HOME/.ssh/identity |
4fe2af09 | 125 | Contains the RSA authentication identity of the user. |
126 | This file should not be readable by anyone but the user. | |
127 | It is possible to | |
bf740959 | 128 | specify a passphrase when generating the key; that passphrase will be |
4fe2af09 | 129 | used to encrypt the private part of this file using 3DES. |
130 | This file is not automatically accessed by | |
bf740959 | 131 | .Nm |
132 | but it is offered as the default file for the private key. | |
133 | .It Pa $HOME/.ssh/identity.pub | |
4fe2af09 | 134 | Contains the public key for authentication. |
135 | The contents of this file should be added to | |
bf740959 | 136 | .Pa $HOME/.ssh/authorized_keys |
137 | on all machines | |
4fe2af09 | 138 | where you wish to log in using RSA authentication. |
139 | There is no need to keep the contents of this file secret. | |
bf740959 | 140 | .Sh AUTHOR |
141 | Tatu Ylonen <ylo@cs.hut.fi> | |
142 | .Pp | |
143 | OpenSSH | |
144 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | |
4fe2af09 | 145 | removed and newer features re-added. |
146 | Rapidly after the 1.2.12 release, | |
147 | newer versions bore successively more restrictive licenses. | |
148 | This version of OpenSSH | |
bf740959 | 149 | .Bl -bullet |
150 | .It | |
371ecff9 | 151 | has all components of a restrictive nature (i.e., patents) |
bf740959 | 152 | directly removed from the source code; any licensed or patented components |
153 | are chosen from | |
154 | external libraries. | |
155 | .It | |
156 | has been updated to support ssh protocol 1.5. | |
157 | .It | |
f54651ce | 158 | contains added support for |
bf740959 | 159 | .Xr kerberos 8 |
160 | authentication and ticket passing. | |
161 | .It | |
162 | supports one-time password authentication with | |
163 | .Xr skey 1 . | |
164 | .El | |
bf740959 | 165 | .Sh SEE ALSO |
166 | .Xr ssh 1 , | |
167 | .Xr ssh-add 1 , | |
0c372277 | 168 | .Xr ssh-agent 1 , |
bf740959 | 169 | .Xr sshd 8 , |