Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.10
1.1 deraadt 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: .\"
1.10 ! markus 12: .\" $Id: ssh-keygen.1,v 1.9 1999/11/16 22:49:28 markus Exp $
1.1 deraadt 13: .\"
1.2 deraadt 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
1.5 aaron 22: .Op Fl q
1.2 deraadt 23: .Op Fl b Ar bits
24: .Op Fl N Ar new_passphrase
25: .Op Fl C Ar comment
1.9 markus 26: .Op Fl f Ar keyfile
1.2 deraadt 27: .Nm ssh-keygen
28: .Fl p
29: .Op Fl P Ar old_passphrase
30: .Op Fl N Ar new_passphrase
1.9 markus 31: .Op Fl f Ar keyfile
1.2 deraadt 32: .Nm ssh-keygen
33: .Fl c
34: .Op Fl P Ar passphrase
35: .Op Fl C Ar comment
1.9 markus 36: .Op Fl f Ar keyfile
37: .Nm ssh-keygen
38: .Fl l
39: .Op Fl f Ar keyfile
1.2 deraadt 40: .Sh DESCRIPTION
41: .Nm
1.1 deraadt 42: generates and manages authentication keys for
1.2 deraadt 43: .Xr ssh 1 .
44: Normally each user wishing to use SSH
1.1 deraadt 45: with RSA authentication runs this once to create the authentication
46: key in
1.2 deraadt 47: .Pa $HOME/.ssh/identity .
1.1 deraadt 48: Additionally, the system administrator may use this to generate host keys.
1.2 deraadt 49: .Pp
1.1 deraadt 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
1.2 deraadt 52: same name but
53: .Dq .pub
54: appended. The program also asks for a
1.1 deraadt 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
1.2 deraadt 61: .Fl p
1.1 deraadt 62: option.
1.2 deraadt 63: .Pp
1.1 deraadt 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.
1.2 deraadt 67: .Pp
1.1 deraadt 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
1.2 deraadt 71: initialized to
72: .Dq user@host
73: when the key is created, but can be changed using the
74: .Fl c
1.1 deraadt 75: option.
1.2 deraadt 76: .Pp
77: The options are as follows:
78: .Bl -tag -width Ds
79: .It Fl b Ar bits
1.1 deraadt 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
83: default is 1024 bits.
1.2 deraadt 84: .It Fl c
1.1 deraadt 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.
1.9 markus 88: .It Fl f
89: Specifies the filename of the key file.
90: .It Fl l
91: Show fingerprint of specified private or public key file.
1.2 deraadt 92: .It Fl p
1.1 deraadt 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
96: new passphrase.
1.5 aaron 97: .It Fl q
98: Silence
99: .Nm ssh-keygen .
100: Used by
101: .Pa /etc/rc
102: when creating a new key.
1.2 deraadt 103: .It Fl C Ar comment
1.1 deraadt 104: Provides the new comment.
1.2 deraadt 105: .It Fl N Ar new_passphrase
1.1 deraadt 106: Provides the new passphrase.
1.2 deraadt 107: .It Fl P Ar passphrase
1.1 deraadt 108: Provides the (old) passphrase.
1.2 deraadt 109: .El
110: .Sh FILES
111: .Bl -tag -width Ds
112: .It Pa $HOME/.ssh/identity
1.1 deraadt 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
1.3 deraadt 116: used to encrypt the private part of this file using 3DES. This file
1.1 deraadt 117: is not automatically accessed by
1.2 deraadt 118: .Nm
1.1 deraadt 119: but it is offered as the default file for the private key.
1.2 deraadt 120: .It Pa $HOME/.ssh/identity.pub
1.1 deraadt 121: Contains the public key for authentication. The contents of this file
1.2 deraadt 122: should be added to
123: .Pa $HOME/.ssh/authorized_keys
124: on all machines
1.1 deraadt 125: where you wish to log in using RSA authentication. There is no
126: need to keep the contents of this file secret.
1.2 deraadt 127: .Sh AUTHOR
1.1 deraadt 128: Tatu Ylonen <ylo@cs.hut.fi>
1.4 deraadt 129: .Pp
1.6 deraadt 130: OpenSSH
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
134: of OpenSSH
135: .Bl -bullet
136: .It
137: has all components of a restrictive nature (ie. patents, see
138: .Xr ssl 8 )
139: directly removed from the source code; any licensed or patented components
140: are chosen from
141: external libraries.
142: .It
143: has been updated to support ssh protocol 1.5.
144: .It
145: contains added support for
146: .Xr kerberos 8
147: authentication and ticket passing.
148: .It
149: supports one-time password authentication with
150: .Xr skey 1 .
151: .El
152: .Pp
153: The libraries described in
1.4 deraadt 154: .Xr ssl 8
155: are required for proper operation.
1.2 deraadt 156: .Sh SEE ALSO
157: .Xr ssh 1 ,
158: .Xr ssh-add 1 ,
1.8 ericj 159: .Xr ssh-agent 1 ,
1.4 deraadt 160: .Xr sshd 8 ,
161: .Xr ssl 8