5 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
7 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8 .\" All rights reserved
10 .\" Created: Sat Apr 22 23:55:14 1995 ylo
14 .Dd September 25, 1999
19 .Nd authentication key generation
24 .Op Fl N Ar new_passphrase
29 .Op Fl P Ar old_passphrase
30 .Op Fl N Ar new_passphrase
34 .Op Fl P Ar passphrase
42 generates and manages authentication keys for
44 Normally each user wishing to use SSH
45 with RSA authentication runs this once to create the authentication
47 .Pa $HOME/.ssh/identity .
48 Additionally, the system administrator may use this to generate host keys.
50 Normally this program generates the key and asks for a file in which
51 to store the private key.
52 The public key is stored in a file with the same name but
55 The program also asks for a passphrase.
56 The passphrase may be empty to indicate no passphrase
57 (host keys must have empty passphrase), or it may be a string of
59 Good passphrases are 10-30 characters long and are
60 not simple sentences or otherwise easily guessable (English
61 prose has only 1-2 bits of entropy per word, and provides very bad
63 The passphrase can be changed later by using the
67 There is no way to recover a lost passphrase.
69 lost or forgotten, you will have to generate a new key and copy the
70 corresponding public key to other machines.
72 There is also a comment field in the key file that is only for
73 convenience to the user to help identify the key.
74 The comment can tell what the key is for, or whatever is useful.
75 The comment is initialized to
77 when the key is created, but can be changed using the
81 The options are as follows:
84 Specifies the number of bits in the key to create.
86 Generally 1024 bits is considered sufficient, and key sizes
87 above that no longer improve security but make things slower.
88 The default is 1024 bits.
90 Requests changing the comment in the private and public key files.
91 The program will prompt for the file containing the private keys, for
92 passphrase if the key has one, and for the new comment.
94 Specifies the filename of the key file.
96 Show fingerprint of specified private or public key file.
98 Requests changing the passphrase of a private key file instead of
99 creating a new private key.
100 The program will prompt for the file
101 containing the private key, for the old passphrase, and twice for the
108 when creating a new key.
110 Provides the new comment.
111 .It Fl N Ar new_passphrase
112 Provides the new passphrase.
113 .It Fl P Ar passphrase
114 Provides the (old) passphrase.
118 .It Pa $HOME/.ssh/identity
119 Contains the RSA authentication identity of the user.
120 This file should not be readable by anyone but the user.
122 specify a passphrase when generating the key; that passphrase will be
123 used to encrypt the private part of this file using 3DES.
124 This file is not automatically accessed by
126 but it is offered as the default file for the private key.
127 .It Pa $HOME/.ssh/identity.pub
128 Contains the public key for authentication.
129 The contents of this file should be added to
130 .Pa $HOME/.ssh/authorized_keys
132 where you wish to log in using RSA authentication.
133 There is no need to keep the contents of this file secret.
135 Tatu Ylonen <ylo@cs.hut.fi>
138 is a derivative of the original (free) ssh 1.2.12 release, but with bugs
139 removed and newer features re-added.
140 Rapidly after the 1.2.12 release,
141 newer versions bore successively more restrictive licenses.
142 This version of OpenSSH
145 has all components of a restrictive nature (i.e., patents, see
147 directly removed from the source code; any licensed or patented components
151 has been updated to support ssh protocol 1.5.
153 contains added support for
155 authentication and ticket passing.
157 supports one-time password authentication with
161 The libraries described in
163 are required for proper operation.