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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 dq | |
23 | .Op Fl b Ar bits | |
24 | .Op Fl N Ar new_passphrase | |
25 | .Op Fl C Ar comment | |
26 | .Op Fl f Ar keyfile | |
27 | .Nm ssh-keygen | |
28 | .Fl p | |
29 | .Op Fl P Ar old_passphrase | |
30 | .Op Fl N Ar new_passphrase | |
31 | .Op Fl f Ar keyfile | |
32 | .Nm ssh-keygen | |
33 | .Fl x | |
34 | .Op Fl f Ar keyfile | |
35 | .Nm ssh-keygen | |
36 | .Fl X | |
37 | .Op Fl f Ar keyfile | |
38 | .Nm ssh-keygen | |
39 | .Fl y | |
40 | .Op Fl f Ar keyfile | |
41 | .Nm ssh-keygen | |
42 | .Fl c | |
43 | .Op Fl P Ar passphrase | |
44 | .Op Fl C Ar comment | |
45 | .Op Fl f Ar keyfile | |
46 | .Nm ssh-keygen | |
47 | .Fl l | |
48 | .Op Fl f Ar keyfile | |
49 | .Nm ssh-keygen | |
50 | .Fl R | |
51 | .Sh DESCRIPTION | |
52 | .Nm | |
53 | generates and manages authentication keys for | |
54 | .Xr ssh 1 . | |
55 | .Nm | |
56 | defaults to generating an RSA key for use by protocols 1.3 and 1.5; | |
57 | specifying the | |
58 | .Fl d | |
59 | flag will create a DSA key instead for use by protocol 2.0. | |
60 | .Pp | |
61 | Normally each user wishing to use SSH | |
62 | with RSA or DSA authentication runs this once to create the authentication | |
63 | key in | |
64 | .Pa $HOME/.ssh/identity | |
65 | or | |
66 | .Pa $HOME/.ssh/id_dsa . | |
67 | Additionally, the system administrator may use this to generate host keys, | |
68 | as seen in | |
69 | .Pa /etc/rc . | |
70 | .Pp | |
71 | Normally this program generates the key and asks for a file in which | |
72 | to store the private key. | |
73 | The public key is stored in a file with the same name but | |
74 | .Dq .pub | |
75 | appended. | |
76 | The program also asks for a passphrase. | |
77 | The passphrase may be empty to indicate no passphrase | |
78 | (host keys must have empty passphrase), or it may be a string of | |
79 | arbitrary length. | |
80 | Good passphrases are 10-30 characters long and are | |
81 | not simple sentences or otherwise easily guessable (English | |
82 | prose has only 1-2 bits of entropy per word, and provides very bad | |
83 | passphrases). | |
84 | The passphrase can be changed later by using the | |
85 | .Fl p | |
86 | option. | |
87 | .Pp | |
88 | There is no way to recover a lost passphrase. | |
89 | If the passphrase is | |
90 | lost or forgotten, you will have to generate a new key and copy the | |
91 | corresponding public key to other machines. | |
92 | .Pp | |
93 | For RSA, there is also a comment field in the key file that is only for | |
94 | convenience to the user to help identify the key. | |
95 | The comment can tell what the key is for, or whatever is useful. | |
96 | The comment is initialized to | |
97 | .Dq user@host | |
98 | when the key is created, but can be changed using the | |
99 | .Fl c | |
100 | option. | |
101 | .Pp | |
102 | After a key is generated, instructions below detail where the keys | |
103 | should be placed to be activated. | |
104 | .Pp | |
105 | The options are as follows: | |
106 | .Bl -tag -width Ds | |
107 | .It Fl b Ar bits | |
108 | Specifies the number of bits in the key to create. | |
109 | Minimum is 512 bits. | |
110 | Generally 1024 bits is considered sufficient, and key sizes | |
111 | above that no longer improve security but make things slower. | |
112 | The default is 1024 bits. | |
113 | .It Fl c | |
114 | Requests changing the comment in the private and public key files. | |
115 | The program will prompt for the file containing the private keys, for | |
116 | passphrase if the key has one, and for the new comment. | |
117 | .It Fl f | |
118 | Specifies the filename of the key file. | |
119 | .It Fl l | |
120 | Show fingerprint of specified private or public key file. | |
121 | .It Fl p | |
122 | Requests changing the passphrase of a private key file instead of | |
123 | creating a new private key. | |
124 | The program will prompt for the file | |
125 | containing the private key, for the old passphrase, and twice for the | |
126 | new passphrase. | |
127 | .It Fl q | |
128 | Silence | |
129 | .Nm ssh-keygen . | |
130 | Used by | |
131 | .Pa /etc/rc | |
132 | when creating a new key. | |
133 | .It Fl C Ar comment | |
134 | Provides the new comment. | |
135 | .It Fl N Ar new_passphrase | |
136 | Provides the new passphrase. | |
137 | .It Fl P Ar passphrase | |
138 | Provides the (old) passphrase. | |
139 | .It Fl R | |
140 | If RSA support is functional, immediately exits with code 0. If RSA | |
141 | support is not functional, exits with code 1. This flag will be | |
142 | removed once the RSA patent expires. | |
143 | .It Fl x | |
144 | This option will read a private | |
145 | OpenSSH DSA format file and print a SSH2-compatible public key to stdout. | |
146 | .It Fl X | |
147 | This option will read a | |
148 | SSH2-compatible public key file and print an OpenSSH DSA compatible public key to stdout. | |
149 | .It Fl y | |
150 | This option will read a private | |
151 | OpenSSH DSA format file and print an OpenSSH DSA public key to stdout. | |
152 | .El | |
153 | .Sh FILES | |
154 | .Bl -tag -width Ds | |
155 | .It Pa $HOME/.ssh/identity | |
156 | Contains the RSA authentication identity of the user. | |
157 | This file should not be readable by anyone but the user. | |
158 | It is possible to | |
159 | specify a passphrase when generating the key; that passphrase will be | |
160 | used to encrypt the private part of this file using 3DES. | |
161 | This file is not automatically accessed by | |
162 | .Nm | |
163 | but it is offered as the default file for the private key. | |
164 | .Xr sshd 8 | |
165 | will read this file when a login attempt is made. | |
166 | .It Pa $HOME/.ssh/identity.pub | |
167 | Contains the public key for authentication. | |
168 | The contents of this file should be added to | |
169 | .Pa $HOME/.ssh/authorized_keys | |
170 | on all machines | |
171 | where you wish to log in using RSA authentication. | |
172 | There is no need to keep the contents of this file secret. | |
173 | .It Pa $HOME/.ssh/id_dsa | |
174 | Contains the DSA authentication identity of the user. | |
175 | This file should not be readable by anyone but the user. | |
176 | It is possible to | |
177 | specify a passphrase when generating the key; that passphrase will be | |
178 | used to encrypt the private part of this file using 3DES. | |
179 | This file is not automatically accessed by | |
180 | .Nm | |
181 | but it is offered as the default file for the private key. | |
182 | .Xr sshd 8 | |
183 | will read this file when a login attempt is made. | |
184 | .It Pa $HOME/.ssh/id_dsa.pub | |
185 | Contains the public key for authentication. | |
186 | The contents of this file should be added to | |
187 | .Pa $HOME/.ssh/authorized_keys2 | |
188 | on all machines | |
189 | where you wish to log in using DSA authentication. | |
190 | There is no need to keep the contents of this file secret. | |
191 | .Sh AUTHOR | |
192 | Tatu Ylonen <ylo@cs.hut.fi> | |
193 | .Pp | |
194 | OpenSSH | |
195 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | |
196 | removed and newer features re-added. | |
197 | Rapidly after the 1.2.12 release, | |
198 | newer versions bore successively more restrictive licenses. | |
199 | This version of OpenSSH | |
200 | .Bl -bullet | |
201 | .It | |
202 | has all components of a restrictive nature (i.e., patents) | |
203 | directly removed from the source code; any licensed or patented components | |
204 | are chosen from | |
205 | external libraries. | |
206 | .It | |
207 | has been updated to support ssh protocol 1.5. | |
208 | .It | |
209 | contains added support for | |
210 | .Xr kerberos 8 | |
211 | authentication and ticket passing. | |
212 | .It | |
213 | supports one-time password authentication with | |
214 | .Xr skey 1 . | |
215 | .El | |
216 | .Sh SEE ALSO | |
217 | .Xr ssh 1 , | |
218 | .Xr ssh-add 1 , | |
219 | .Xr ssh-agent 1 , | |
220 | .Xr sshd 8 , |