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
28 .Op Fl P Ar old_passphrase
29 .Op Fl N Ar new_passphrase
32 .Op Fl P Ar passphrase
36 generates and manages authentication keys for
38 Normally each user wishing to use SSH
39 with RSA authentication runs this once to create the authentication
41 .Pa $HOME/.ssh/identity .
42 Additionally, the system administrator may use this to generate host keys.
44 Normally this program generates the key and asks for a file in which
45 to store the private key. The public key is stored in a file with the
48 appended. The program also asks for a
49 passphrase. The passphrase may be empty to indicate no passphrase
50 (host keys must have empty passphrase), or it may be a string of
51 arbitrary length. Good passphrases are 10-30 characters long and are
52 not simple sentences or otherwise easily guessable (English
53 prose has only 1-2 bits of entropy per word, and provides very bad
54 passphrases). The passphrase can be changed later by using the
58 There is no way to recover a lost passphrase. If the passphrase is
59 lost or forgotten, you will have to generate a new key and copy the
60 corresponding public key to other machines.
62 There is also a comment field in the key file that is only for
63 convenience to the user to help identify the key. The comment can
64 tell what the key is for, or whatever is useful. The comment is
67 when the key is created, but can be changed using the
71 The options are as follows:
74 Specifies the number of bits in the key to create. Minimum is 512
75 bits. Generally 1024 bits is considered sufficient, and key sizes
76 above that no longer improve security but make things slower. The
79 Requests changing the comment in the private and public key files.
80 The program will prompt for the file containing the private keys, for
81 passphrase if the key has one, and for the new comment.
83 Requests changing the passphrase of a private key file instead of
84 creating a new private key. The program will prompt for the file
85 containing the private key, for the old passphrase, and twice for the
92 when creating a new key.
94 Provides the new comment.
95 .It Fl N Ar new_passphrase
96 Provides the new passphrase.
97 .It Fl P Ar passphrase
98 Provides the (old) passphrase.
102 .It Pa $HOME/.ssh/random_seed
103 Used for seeding the random number generator. This file should not be
104 readable by anyone but the user. This file is created the first time
105 the program is run, and is updated every time.
106 .It Pa $HOME/.ssh/identity
107 Contains the RSA authentication identity of the user. This file
108 should not be readable by anyone but the user. It is possible to
109 specify a passphrase when generating the key; that passphrase will be
110 used to encrypt the private part of this file using 3DES. This file
111 is not automatically accessed by
113 but it is offered as the default file for the private key.
114 .It Pa $HOME/.ssh/identity.pub
115 Contains the public key for authentication. The contents of this file
117 .Pa $HOME/.ssh/authorized_keys
119 where you wish to log in using RSA authentication. There is no
120 need to keep the contents of this file secret.
122 Tatu Ylonen <ylo@cs.hut.fi>
125 is a derivative of the original (free) ssh 1.2.12 release, but with bugs
126 removed and newer features re-added. Rapidly after the 1.2.12 release,
127 newer versions bore successively more restrictive licenses. This version
131 has all components of a restrictive nature (ie. patents, see
133 directly removed from the source code; any licensed or patented components
137 has been updated to support ssh protocol 1.5.
139 contains added support for
141 authentication and ticket passing.
143 supports one-time password authentication with
147 The libraries described in
149 are required for proper operation.