ssh-keygen.1 - security/openssh-library - Rivoreo Source Code Repositories

 .\"  -*- nroff -*-
 .\"
 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 .\"                    All rights reserved
 .\"
 .\" As far as I am concerned, the code I have written for this software
 .\" can be used freely for any purpose.  Any derived versions of this
 .\" software must be clearly marked as such, and if the derived work is
 .\" incompatible with the protocol description in the RFC file, it must be
 .\" called by a name other than "ssh" or "Secure Shell".
 .\"
 .\"
 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
 .Dd September 25, 1999
 .Dt SSH-KEYGEN 1
 .Os
 .Sh NAME
 .Nm ssh-keygen
 .Nd authentication key generation
 .Sh SYNOPSIS
 .Nm ssh-keygen
 .Op Fl dq
 .Op Fl b Ar bits
 .Op Fl N Ar new_passphrase
 .Op Fl C Ar comment
 .Op Fl f Ar output_keyfile
 .Nm ssh-keygen
 .Fl p
 .Op Fl P Ar old_passphrase
 .Op Fl N Ar new_passphrase
 .Op Fl f Ar keyfile
 .Nm ssh-keygen
 .Fl x
 .Op Fl f Ar input_keyfile
 .Nm ssh-keygen
 .Fl X
 .Op Fl f Ar input_keyfile
 .Nm ssh-keygen
 .Fl y
 .Op Fl f Ar input_keyfile
 .Nm ssh-keygen
 .Fl c
 .Op Fl P Ar passphrase
 .Op Fl C Ar comment
 .Op Fl f Ar keyfile
 .Nm ssh-keygen
 .Fl l
 .Op Fl f Ar input_keyfile
 .Nm ssh-keygen
 .Fl R
 .Sh DESCRIPTION
 .Nm
 generates and manages authentication keys for
 .Xr ssh 1 .
 .Nm
 defaults to generating an RSA key for use by protocols 1.3 and 1.5;
 specifying the
 .Fl d
 flag will create a DSA key instead for use by protocol 2.0.
 .Pp
 Normally each user wishing to use SSH
 with RSA or DSA authentication runs this once to create the authentication
 key in
 .Pa $HOME/.ssh/identity
 or
 .Pa $HOME/.ssh/id_dsa .
 Additionally, the system administrator may use this to generate host keys,
 as seen in
 .Pa /etc/rc .
 .Pp
 Normally this program generates the key and asks for a file in which
 to store the private key.
 The public key is stored in a file with the same name but
 .Dq .pub
 appended.
 The program also asks for a passphrase.
 The passphrase may be empty to indicate no passphrase
 (host keys must have empty passphrase), or it may be a string of
 arbitrary length.
 Good passphrases are 10-30 characters long and are
 not simple sentences or otherwise easily guessable (English
 prose has only 1-2 bits of entropy per word, and provides very bad
 passphrases).
 The passphrase can be changed later by using the
 .Fl p
 option.
 .Pp
 There is no way to recover a lost passphrase.
 If the passphrase is
 lost or forgotten, you will have to generate a new key and copy the
 corresponding public key to other machines.
 .Pp
 For RSA, there is also a comment field in the key file that is only for
 convenience to the user to help identify the key.
 The comment can tell what the key is for, or whatever is useful.
 The comment is initialized to
 .Dq user@host
 when the key is created, but can be changed using the
 .Fl c
 option.
 .Pp
 After a key is generated, instructions below detail where the keys
 should be placed to be activated.
 .Pp
 The options are as follows:
 .Bl -tag -width Ds
 .It Fl b Ar bits
 Specifies the number of bits in the key to create.
 Minimum is 512 bits.
 Generally 1024 bits is considered sufficient, and key sizes
 above that no longer improve security but make things slower.
 The default is 1024 bits.
 .It Fl c
 Requests changing the comment in the private and public key files.
 The program will prompt for the file containing the private keys, for
 passphrase if the key has one, and for the new comment.
 .It Fl f
 Specifies the filename of the key file.
 .It Fl l
 Show fingerprint of specified private or public key file.
 .It Fl p
 Requests changing the passphrase of a private key file instead of
 creating a new private key.
 The program will prompt for the file
 containing the private key, for the old passphrase, and twice for the
 new passphrase.
 .It Fl q
 Silence
 .Nm ssh-keygen .
 Used by
 .Pa /etc/rc
 when creating a new key.
 .It Fl C Ar comment
 Provides the new comment.
 .It Fl N Ar new_passphrase
 Provides the new passphrase.
 .It Fl P Ar passphrase
 Provides the (old) passphrase.
 .It Fl R
 If RSA support is functional, immediately exits with code 0.  If RSA
 support is not functional, exits with code 1.  This flag will be
 removed once the RSA patent expires.
 .It Fl x
 This option will read a private
 OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
 .It Fl X
 This option will read a unencrypted
 SSH2-compatible private (or public) key file and
 print an OpenSSH compatible private (or public) key to stdout.
 .It Fl y
 This option will read a private
 OpenSSH DSA format file and print an OpenSSH DSA public key to stdout.
 .El
 .Sh FILES
 .Bl -tag -width Ds
 .It Pa $HOME/.ssh/identity
 Contains the RSA authentication identity of the user.
 This file should not be readable by anyone but the user.
 It is possible to
 specify a passphrase when generating the key; that passphrase will be
 used to encrypt the private part of this file using 3DES.
 This file is not automatically accessed by
 .Nm
 but it is offered as the default file for the private key.
 .Xr sshd 8
 will read this file when a login attempt is made.
 .It Pa $HOME/.ssh/identity.pub
 Contains the public key for authentication.
 The contents of this file should be added to
 .Pa $HOME/.ssh/authorized_keys
 on all machines
 where you wish to log in using RSA authentication.
 There is no need to keep the contents of this file secret.
 .It Pa $HOME/.ssh/id_dsa
 Contains the DSA authentication identity of the user.
 This file should not be readable by anyone but the user.
 It is possible to
 specify a passphrase when generating the key; that passphrase will be
 used to encrypt the private part of this file using 3DES.
 This file is not automatically accessed by
 .Nm
 but it is offered as the default file for the private key.
 .Xr sshd 8
 will read this file when a login attempt is made.
 .It Pa $HOME/.ssh/id_dsa.pub
 Contains the public key for authentication.
 The contents of this file should be added to
 .Pa $HOME/.ssh/authorized_keys2
 on all machines
 where you wish to log in using DSA authentication.
 There is no need to keep the contents of this file secret.
 .El
 .Sh AUTHOR
 Tatu Ylonen <ylo@cs.hut.fi>
 .Pp
 OpenSSH
 is a derivative of the original (free) ssh 1.2.12 release, but with bugs
 removed and newer features re-added.
 Rapidly after the 1.2.12 release,
 newer versions bore successively more restrictive licenses.
 This version of OpenSSH
 .Bl -bullet
 .It
 has all components of a restrictive nature (i.e., patents, see
 .Xr crypto 3 )
 directly removed from the source code; any licensed or patented components
 are chosen from
 external libraries.
 .It
 has been updated to support ssh protocol 1.5.
 .It
 contains added support for
 .Xr kerberos 8
 authentication and ticket passing.
 .It
 supports one-time password authentication with
 .Xr skey 1 .
 .El
 .Sh SEE ALSO
 .Xr ssh 1 ,
 .Xr ssh-add 1 ,
 .Xr ssh-agent 1 ,
 .Xr sshd 8 ,
 .Xr crypto 3
	.\" -- nroff --
	.\"
	.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
	.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
	.\" All rights reserved
	.\"
	.\" As far as I am concerned, the code I have written for this software
	.\" can be used freely for any purpose. Any derived versions of this
	.\" software must be clearly marked as such, and if the derived work is
	.\" incompatible with the protocol description in the RFC file, it must be
	.\" called by a name other than "ssh" or "Secure Shell".
	.\"
	.\"
	.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
	.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
	.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
	.\"
	.\" Redistribution and use in source and binary forms, with or without
	.\" modification, are permitted provided that the following conditions
	.\" are met:
	.\" 1. Redistributions of source code must retain the above copyright
	.\" notice, this list of conditions and the following disclaimer.
	.\" 2. Redistributions in binary form must reproduce the above copyright
	.\" notice, this list of conditions and the following disclaimer in the
	.\" documentation and/or other materials provided with the distribution.
	.\"
	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	.\"
	.Dd September 25, 1999
	.Dt SSH-KEYGEN 1
	.Os
	.Sh NAME
	.Nm ssh-keygen
	.Nd authentication key generation
	.Sh SYNOPSIS
	.Nm ssh-keygen
	.Op Fl dq
	.Op Fl b Ar bits
	.Op Fl N Ar new_passphrase
	.Op Fl C Ar comment
	.Op Fl f Ar output_keyfile
	.Nm ssh-keygen
	.Fl p
	.Op Fl P Ar old_passphrase
	.Op Fl N Ar new_passphrase
	.Op Fl f Ar keyfile
	.Nm ssh-keygen
	.Fl x
	.Op Fl f Ar input_keyfile
	.Nm ssh-keygen
	.Fl X
	.Op Fl f Ar input_keyfile
	.Nm ssh-keygen
	.Fl y
	.Op Fl f Ar input_keyfile
	.Nm ssh-keygen
	.Fl c
	.Op Fl P Ar passphrase
	.Op Fl C Ar comment
	.Op Fl f Ar keyfile
	.Nm ssh-keygen
	.Fl l
	.Op Fl f Ar input_keyfile
	.Nm ssh-keygen
	.Fl R
	.Sh DESCRIPTION
	.Nm
	generates and manages authentication keys for
	.Xr ssh 1 .
	.Nm
	defaults to generating an RSA key for use by protocols 1.3 and 1.5;
	specifying the
	.Fl d
	flag will create a DSA key instead for use by protocol 2.0.
	.Pp
	Normally each user wishing to use SSH
	with RSA or DSA authentication runs this once to create the authentication
	key in
	.Pa $HOME/.ssh/identity
	or
	.Pa $HOME/.ssh/id_dsa .
	Additionally, the system administrator may use this to generate host keys,
	as seen in
	.Pa /etc/rc .
	.Pp
	Normally this program generates the key and asks for a file in which
	to store the private key.
	The public key is stored in a file with the same name but
	.Dq .pub
	appended.
	The program also asks for a passphrase.
	The passphrase may be empty to indicate no passphrase
	(host keys must have empty passphrase), or it may be a string of
	arbitrary length.
	Good passphrases are 10-30 characters long and are
	not simple sentences or otherwise easily guessable (English
	prose has only 1-2 bits of entropy per word, and provides very bad
	passphrases).
	The passphrase can be changed later by using the
	.Fl p
	option.
	.Pp
	There is no way to recover a lost passphrase.
	If the passphrase is
	lost or forgotten, you will have to generate a new key and copy the
	corresponding public key to other machines.
	.Pp
	For RSA, there is also a comment field in the key file that is only for
	convenience to the user to help identify the key.
	The comment can tell what the key is for, or whatever is useful.
	The comment is initialized to
	.Dq user@host
	when the key is created, but can be changed using the
	.Fl c
	option.
	.Pp
	After a key is generated, instructions below detail where the keys
	should be placed to be activated.
	.Pp
	The options are as follows:
	.Bl -tag -width Ds
	.It Fl b Ar bits
	Specifies the number of bits in the key to create.
	Minimum is 512 bits.
	Generally 1024 bits is considered sufficient, and key sizes
	above that no longer improve security but make things slower.
	The default is 1024 bits.
	.It Fl c
	Requests changing the comment in the private and public key files.
	The program will prompt for the file containing the private keys, for
	passphrase if the key has one, and for the new comment.
	.It Fl f
	Specifies the filename of the key file.
	.It Fl l
	Show fingerprint of specified private or public key file.
	.It Fl p
	Requests changing the passphrase of a private key file instead of
	creating a new private key.
	The program will prompt for the file
	containing the private key, for the old passphrase, and twice for the
	new passphrase.
	.It Fl q
	Silence
	.Nm ssh-keygen .
	Used by
	.Pa /etc/rc
	when creating a new key.
	.It Fl C Ar comment
	Provides the new comment.
	.It Fl N Ar new_passphrase
	Provides the new passphrase.
	.It Fl P Ar passphrase
	Provides the (old) passphrase.
	.It Fl R
	If RSA support is functional, immediately exits with code 0. If RSA
	support is not functional, exits with code 1. This flag will be
	removed once the RSA patent expires.
	.It Fl x
	This option will read a private
	OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
	.It Fl X
	This option will read a unencrypted
	SSH2-compatible private (or public) key file and
	print an OpenSSH compatible private (or public) key to stdout.
	.It Fl y
	This option will read a private
	OpenSSH DSA format file and print an OpenSSH DSA public key to stdout.
	.El
	.Sh FILES
	.Bl -tag -width Ds
	.It Pa $HOME/.ssh/identity
	Contains the RSA authentication identity of the user.
	This file should not be readable by anyone but the user.
	It is possible to
	specify a passphrase when generating the key; that passphrase will be
	used to encrypt the private part of this file using 3DES.
	This file is not automatically accessed by
	.Nm
	but it is offered as the default file for the private key.
	.Xr sshd 8
	will read this file when a login attempt is made.
	.It Pa $HOME/.ssh/identity.pub
	Contains the public key for authentication.
	The contents of this file should be added to
	.Pa $HOME/.ssh/authorized_keys
	on all machines
	where you wish to log in using RSA authentication.
	There is no need to keep the contents of this file secret.
	.It Pa $HOME/.ssh/id_dsa
	Contains the DSA authentication identity of the user.
	This file should not be readable by anyone but the user.
	It is possible to
	specify a passphrase when generating the key; that passphrase will be
	used to encrypt the private part of this file using 3DES.
	This file is not automatically accessed by
	.Nm
	but it is offered as the default file for the private key.
	.Xr sshd 8
	will read this file when a login attempt is made.
	.It Pa $HOME/.ssh/id_dsa.pub
	Contains the public key for authentication.
	The contents of this file should be added to
	.Pa $HOME/.ssh/authorized_keys2
	on all machines
	where you wish to log in using DSA authentication.
	There is no need to keep the contents of this file secret.
	.El
	.Sh AUTHOR
	Tatu Ylonen <ylo@cs.hut.fi>
	.Pp
	OpenSSH
	is a derivative of the original (free) ssh 1.2.12 release, but with bugs
	removed and newer features re-added.
	Rapidly after the 1.2.12 release,
	newer versions bore successively more restrictive licenses.
	This version of OpenSSH
	.Bl -bullet
	.It
	has all components of a restrictive nature (i.e., patents, see
	.Xr crypto 3 )
	directly removed from the source code; any licensed or patented components
	are chosen from
	external libraries.
	.It
	has been updated to support ssh protocol 1.5.
	.It
	contains added support for
	.Xr kerberos 8
	authentication and ticket passing.
	.It
	supports one-time password authentication with
	.Xr skey 1 .
	.El
	.Sh SEE ALSO
	.Xr ssh 1 ,
	.Xr ssh-add 1 ,
	.Xr ssh-agent 1 ,
	.Xr sshd 8 ,
	.Xr crypto 3