281 lines
9.2 KiB
Groff
281 lines
9.2 KiB
Groff
.\" $OpenBSD: ssh-keygen.1,v 1.40 2001/04/23 21:57:07 markus Exp $
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.\"
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.\" -*- nroff -*-
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.\"
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.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
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.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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.\" All rights reserved
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.\"
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.\" As far as I am concerned, the code I have written for this software
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.\" can be used freely for any purpose. Any derived versions of this
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.\" software must be clearly marked as such, and if the derived work is
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.\" incompatible with the protocol description in the RFC file, it must be
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.\" called by a name other than "ssh" or "Secure Shell".
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.\"
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.\"
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.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
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.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
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.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd September 25, 1999
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.Dt SSH-KEYGEN 1
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.Os
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.Sh NAME
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.Nm ssh-keygen
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.Nd authentication key generation, management and conversion
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.Sh SYNOPSIS
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.Nm ssh-keygen
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.Op Fl q
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.Op Fl b Ar bits
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.Op Fl t Ar type
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.Op Fl N Ar new_passphrase
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.Op Fl C Ar comment
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.Op Fl f Ar output_keyfile
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.Nm ssh-keygen
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.Fl p
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.Op Fl P Ar old_passphrase
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.Op Fl N Ar new_passphrase
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.Op Fl f Ar keyfile
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.Nm ssh-keygen
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.Fl i
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.Op Fl f Ar input_keyfile
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.Nm ssh-keygen
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.Fl e
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.Op Fl f Ar input_keyfile
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.Nm ssh-keygen
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.Fl y
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.Op Fl f Ar input_keyfile
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.Nm ssh-keygen
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.Fl c
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.Op Fl P Ar passphrase
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.Op Fl C Ar comment
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.Op Fl f Ar keyfile
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.Nm ssh-keygen
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.Fl l
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.Op Fl f Ar input_keyfile
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.Nm ssh-keygen
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.Fl B
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.Op Fl f Ar input_keyfile
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.Sh DESCRIPTION
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.Nm
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generates, manages and converts authentication keys for
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.Xr ssh 1 .
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.Nm
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defaults to generating a RSA1 key for use by SSH protocol version 1.
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specifying the
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.Fl t
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option allows you to create a key for use by SSH protocol version 2.
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.Pp
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Normally each user wishing to use SSH
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with RSA or DSA authentication runs this once to create the authentication
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key in
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.Pa $HOME/.ssh/identity ,
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.Pa $HOME/.ssh/id_dsa
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or
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.Pa $HOME/.ssh/id_rsa .
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Additionally, the system administrator may use this to generate host keys,
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as seen in
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.Pa /etc/rc .
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.Pp
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Normally this program generates the key and asks for a file in which
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to store the private key.
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The public key is stored in a file with the same name but
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.Dq .pub
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appended.
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The program also asks for a passphrase.
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The passphrase may be empty to indicate no passphrase
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(host keys must have an empty passphrase), or it may be a string of
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arbitrary length.
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Good passphrases are 10-30 characters long and are
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not simple sentences or otherwise easily guessable (English
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prose has only 1-2 bits of entropy per word, and provides very bad
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passphrases).
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The passphrase can be changed later by using the
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.Fl p
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option.
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.Pp
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There is no way to recover a lost passphrase.
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If the passphrase is
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lost or forgotten, you will have to generate a new key and copy the
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corresponding public key to other machines.
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.Pp
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For RSA1 keys,
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there is also a comment field in the key file that is only for
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convenience to the user to help identify the key.
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The comment can tell what the key is for, or whatever is useful.
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The comment is initialized to
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.Dq user@host
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when the key is created, but can be changed using the
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.Fl c
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option.
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.Pp
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After a key is generated, instructions below detail where the keys
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should be placed to be activated.
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl b Ar bits
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Specifies the number of bits in the key to create.
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Minimum is 512 bits.
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Generally 1024 bits is considered sufficient, and key sizes
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above that no longer improve security but make things slower.
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The default is 1024 bits.
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.It Fl c
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Requests changing the comment in the private and public key files.
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The program will prompt for the file containing the private keys, for
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passphrase if the key has one, and for the new comment.
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.It Fl e
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This option will read a private or public OpenSSH key file and
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print the key in a
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.Sq SECSH Public Key File Format
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to stdout.
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This option allows exporting keys for use by several commercial
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SSH implementations.
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.It Fl f
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Specifies the filename of the key file.
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.It Fl i
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This option will read an unencrypted private (or public) key file
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in SSH2-compatible format and print an OpenSSH compatible private
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(or public) key to stdout.
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.Nm
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also reads the
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.Sq SECSH Public Key File Format .
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This option allows importing keys from several commercial
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SSH implementations.
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.It Fl l
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Show fingerprint of specified private or public key file.
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.It Fl p
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Requests changing the passphrase of a private key file instead of
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creating a new private key.
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The program will prompt for the file
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containing the private key, for the old passphrase, and twice for the
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new passphrase.
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.It Fl q
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Silence
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.Nm ssh-keygen .
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Used by
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.Pa /etc/rc
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when creating a new key.
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.It Fl y
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This option will read a private
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OpenSSH format file and print an OpenSSH public key to stdout.
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.It Fl t Ar type
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Specifies the type of the key to create.
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The possible values are
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.Dq rsa1
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for protocol version 1 and
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.Dq rsa
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or
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.Dq dsa
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for protocol version 2.
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The default is
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.Dq rsa1 .
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.It Fl B
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Show the bubblebabble digest of specified private or public key file.
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.It Fl C Ar comment
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Provides the new comment.
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.It Fl N Ar new_passphrase
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Provides the new passphrase.
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.It Fl P Ar passphrase
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Provides the (old) passphrase.
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.El
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.Sh FILES
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.Bl -tag -width Ds
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.It Pa $HOME/.ssh/identity
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Contains the protocol version 1 RSA authentication identity of the user.
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This file should not be readable by anyone but the user.
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It is possible to
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specify a passphrase when generating the key; that passphrase will be
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used to encrypt the private part of this file using 3DES.
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This file is not automatically accessed by
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.Nm
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but it is offered as the default file for the private key.
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.Xr sshd 8
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will read this file when a login attempt is made.
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.It Pa $HOME/.ssh/identity.pub
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Contains the protocol version 1 RSA public key for authentication.
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The contents of this file should be added to
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.Pa $HOME/.ssh/authorized_keys
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on all machines
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where you wish to log in using RSA authentication.
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There is no need to keep the contents of this file secret.
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.It Pa $HOME/.ssh/id_dsa
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Contains the protocol version 2 DSA authentication identity of the user.
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This file should not be readable by anyone but the user.
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It is possible to
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specify a passphrase when generating the key; that passphrase will be
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used to encrypt the private part of this file using 3DES.
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This file is not automatically accessed by
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.Nm
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but it is offered as the default file for the private key.
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.Xr sshd 8
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will read this file when a login attempt is made.
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.It Pa $HOME/.ssh/id_dsa.pub
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Contains the protocol version 2 DSA public key for authentication.
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The contents of this file should be added to
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.Pa $HOME/.ssh/authorized_keys2
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on all machines
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where you wish to log in using public key authentication.
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There is no need to keep the contents of this file secret.
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.It Pa $HOME/.ssh/id_rsa
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Contains the protocol version 2 RSA authentication identity of the user.
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This file should not be readable by anyone but the user.
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It is possible to
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specify a passphrase when generating the key; that passphrase will be
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used to encrypt the private part of this file using 3DES.
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This file is not automatically accessed by
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.Nm
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but it is offered as the default file for the private key.
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.Xr sshd 8
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will read this file when a login attempt is made.
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.It Pa $HOME/.ssh/id_rsa.pub
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Contains the protocol version 2 RSA public key for authentication.
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The contents of this file should be added to
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.Pa $HOME/.ssh/authorized_keys2
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on all machines
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where you wish to log in using public key authentication.
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There is no need to keep the contents of this file secret.
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.El
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.Sh AUTHORS
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OpenSSH is a derivative of the original and free
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ssh 1.2.12 release by Tatu Ylonen.
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Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
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Theo de Raadt and Dug Song
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removed many bugs, re-added newer features and
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created OpenSSH.
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Markus Friedl contributed the support for SSH
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protocol versions 1.5 and 2.0.
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.Sh SEE ALSO
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.Xr ssh 1 ,
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.Xr ssh-add 1 ,
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.Xr ssh-agent 1 ,
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.Xr sshd 8
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.Rs
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.%A J. Galbraith
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.%A R. Thayer
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.%T "SECSH Public Key File Format"
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.%N draft-ietf-secsh-publickeyfile-01.txt
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.%D March 2001
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.%O work in progress material
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.Re
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