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. The public key is stored in a file with the
54 appended. The program also asks for a
55 passphrase. The passphrase may be empty to indicate no passphrase
56 (host keys must have empty passphrase), or it may be a string of
57 arbitrary length. Good passphrases are 10-30 characters long and are
58 not simple sentences or otherwise easily guessable (English
59 prose has only 1-2 bits of entropy per word, and provides very bad
60 passphrases). The passphrase can be changed later by using the
64 There is no way to recover a lost passphrase. If the passphrase is
65 lost or forgotten, you will have to generate a new key and copy the
66 corresponding public key to other machines.
68 There is also a comment field in the key file that is only for
69 convenience to the user to help identify the key. The comment can
70 tell what the key is for, or whatever is useful. The comment is
73 when the key is created, but can be changed using the
77 The options are as follows:
80 Specifies the number of bits in the key to create. Minimum is 512
81 bits. Generally 1024 bits is considered sufficient, and key sizes
82 above that no longer improve security but make things slower. The
85 Requests changing the comment in the private and public key files.
86 The program will prompt for the file containing the private keys, for
87 passphrase if the key has one, and for the new comment.
89 Specifies the filename of the key file.
91 Show fingerprint of specified private or public key file.
93 Requests changing the passphrase of a private key file instead of
94 creating a new private key. The program will prompt for the file
95 containing the private key, for the old passphrase, and twice for the
102 when creating a new key.
104 Provides the new comment.
105 .It Fl N Ar new_passphrase
106 Provides the new passphrase.
107 .It Fl P Ar passphrase
108 Provides the (old) passphrase.
112 .It Pa $HOME/.ssh/identity
113 Contains the RSA authentication identity of the user. This file
114 should not be readable by anyone but the user. It is possible to
115 specify a passphrase when generating the key; that passphrase will be
116 used to encrypt the private part of this file using 3DES. This file
117 is not automatically accessed by
119 but it is offered as the default file for the private key.
120 .It Pa $HOME/.ssh/identity.pub
121 Contains the public key for authentication. The contents of this file
123 .Pa $HOME/.ssh/authorized_keys
125 where you wish to log in using RSA authentication. There is no
126 need to keep the contents of this file secret.
128 Tatu Ylonen <ylo@cs.hut.fi>
131 is a derivative of the original (free) ssh 1.2.12 release, but with bugs
132 removed and newer features re-added. Rapidly after the 1.2.12 release,
133 newer versions bore successively more restrictive licenses. This version
137 has all components of a restrictive nature (i.e., patents, see
139 directly removed from the source code; any licensed or patented components
143 has been updated to support ssh protocol 1.5.
145 contains added support for
147 authentication and ticket passing.
149 supports one-time password authentication with
153 The libraries described in
155 are required for proper operation.