1.\" $OpenBSD: ssh-keygen.1,v 1.48 2001/08/02 15:07:23 jakob Exp $ 2.\" 3.\" -*- nroff -*- 4.\" 5.\" Author: Tatu Ylonen <ylo@cs.hut.fi> 6.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7.\" All rights reserved 8.\" 9.\" As far as I am concerned, the code I have written for this software 10.\" can be used freely for any purpose. Any derived versions of this 11.\" software must be clearly marked as such, and if the derived work is 12.\" incompatible with the protocol description in the RFC file, it must be 13.\" called by a name other than "ssh" or "Secure Shell". 14.\" 15.\" 16.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. 17.\" Copyright (c) 1999 Aaron Campbell. All rights reserved. 18.\" Copyright (c) 1999 Theo de Raadt. All rights reserved. 19.\" 20.\" Redistribution and use in source and binary forms, with or without 21.\" modification, are permitted provided that the following conditions 22.\" are met: 23.\" 1. Redistributions of source code must retain the above copyright 24.\" notice, this list of conditions and the following disclaimer. 25.\" 2. Redistributions in binary form must reproduce the above copyright 26.\" notice, this list of conditions and the following disclaimer in the 27.\" documentation and/or other materials provided with the distribution. 28.\" 29.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 30.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 31.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 32.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 33.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 34.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 38.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39.\" 40.Dd September 25, 1999 41.Dt SSH-KEYGEN 1 42.Os 43.Sh NAME 44.Nm ssh-keygen 45.Nd authentication key generation, management and conversion 46.Sh SYNOPSIS 47.Nm ssh-keygen 48.Op Fl q 49.Op Fl b Ar bits 50.Op Fl t Ar type 51.Op Fl N Ar new_passphrase 52.Op Fl C Ar comment 53.Op Fl f Ar output_keyfile 54.Nm ssh-keygen 55.Fl p 56.Op Fl P Ar old_passphrase 57.Op Fl N Ar new_passphrase 58.Op Fl f Ar keyfile 59.Nm ssh-keygen 60.Fl i 61.Op Fl f Ar input_keyfile 62.Nm ssh-keygen 63.Fl e 64.Op Fl f Ar input_keyfile 65.Nm ssh-keygen 66.Fl y 67.Op Fl f Ar input_keyfile 68.Nm ssh-keygen 69.Fl c 70.Op Fl P Ar passphrase 71.Op Fl C Ar comment 72.Op Fl f Ar keyfile 73.Nm ssh-keygen 74.Fl l 75.Op Fl f Ar input_keyfile 76.Nm ssh-keygen 77.Fl B 78.Op Fl f Ar input_keyfile 79.Nm ssh-keygen 80.Fl D Ar reader 81.Nm ssh-keygen 82.Fl U Ar reader 83.Op Fl f Ar input_keyfile 84.Sh DESCRIPTION 85.Nm 86generates, manages and converts authentication keys for 87.Xr ssh 1 . 88.Nm 89defaults to generating a RSA1 key for use by SSH protocol version 1. 90Specifying the 91.Fl t 92option allows you to create a key for use by SSH protocol version 2. 93.Pp 94Normally each user wishing to use SSH 95with RSA or DSA authentication runs this once to create the authentication 96key in 97.Pa $HOME/.ssh/identity , 98.Pa $HOME/.ssh/id_dsa 99or 100.Pa $HOME/.ssh/id_rsa . 101Additionally, the system administrator may use this to generate host keys, 102as seen in 103.Pa /etc/rc . 104.Pp 105Normally this program generates the key and asks for a file in which 106to store the private key. 107The public key is stored in a file with the same name but 108.Dq .pub 109appended. 110The program also asks for a passphrase. 111The passphrase may be empty to indicate no passphrase 112(host keys must have an empty passphrase), or it may be a string of 113arbitrary length. 114Good passphrases are 10-30 characters long and are 115not simple sentences or otherwise easily guessable (English 116prose has only 1-2 bits of entropy per character, and provides very bad 117passphrases). 118The passphrase can be changed later by using the 119.Fl p 120option. 121.Pp 122There is no way to recover a lost passphrase. 123If the passphrase is 124lost or forgotten, you will have to generate a new key and copy the 125corresponding public key to other machines. 126.Pp 127For RSA1 keys, 128there is also a comment field in the key file that is only for 129convenience to the user to help identify the key. 130The comment can tell what the key is for, or whatever is useful. 131The comment is initialized to 132.Dq user@host 133when the key is created, but can be changed using the 134.Fl c 135option. 136.Pp 137After a key is generated, instructions below detail where the keys 138should be placed to be activated. 139.Pp 140The options are as follows: 141.Bl -tag -width Ds 142.It Fl b Ar bits 143Specifies the number of bits in the key to create. 144Minimum is 512 bits. 145Generally 1024 bits is considered sufficient, and key sizes 146above that no longer improve security but make things slower. 147The default is 1024 bits. 148.It Fl c 149Requests changing the comment in the private and public key files. 150The program will prompt for the file containing the private keys, for 151the passphrase if the key has one, and for the new comment. 152.It Fl e 153This option will read a private or public OpenSSH key file and 154print the key in a 155.Sq SECSH Public Key File Format 156to stdout. 157This option allows exporting keys for use by several commercial 158SSH implementations. 159.It Fl f Ar filename 160Specifies the filename of the key file. 161.It Fl i 162This option will read an unencrypted private (or public) key file 163in SSH2-compatible format and print an OpenSSH compatible private 164(or public) key to stdout. 165.Nm 166also reads the 167.Sq SECSH Public Key File Format . 168This option allows importing keys from several commercial 169SSH implementations. 170.It Fl l 171Show fingerprint of specified private or public key file. 172.It Fl p 173Requests changing the passphrase of a private key file instead of 174creating a new private key. 175The program will prompt for the file 176containing the private key, for the old passphrase, and twice for the 177new passphrase. 178.It Fl q 179Silence 180.Nm ssh-keygen . 181Used by 182.Pa /etc/rc 183when creating a new key. 184.It Fl y 185This option will read a private 186OpenSSH format file and print an OpenSSH public key to stdout. 187.It Fl t Ar type 188Specifies the type of the key to create. 189The possible values are 190.Dq rsa1 191for protocol version 1 and 192.Dq rsa 193or 194.Dq dsa 195for protocol version 2. 196The default is 197.Dq rsa1 . 198.It Fl B 199Show the bubblebabble digest of specified private or public key file. 200.It Fl C Ar comment 201Provides the new comment. 202.It Fl D Ar reader 203Download the RSA public key stored in the smartcard in 204.Ar reader . 205.It Fl N Ar new_passphrase 206Provides the new passphrase. 207.It Fl P Ar passphrase 208Provides the (old) passphrase. 209.It Fl U Ar reader 210Upload an existing RSA private key into the smartcard in 211.Ar reader . 212.El 213.Sh FILES 214.Bl -tag -width Ds 215.It Pa $HOME/.ssh/identity 216Contains the protocol version 1 RSA authentication identity of the user. 217This file should not be readable by anyone but the user. 218It is possible to 219specify a passphrase when generating the key; that passphrase will be 220used to encrypt the private part of this file using 3DES. 221This file is not automatically accessed by 222.Nm 223but it is offered as the default file for the private key. 224.Xr ssh 1 225will read this file when a login attempt is made. 226.It Pa $HOME/.ssh/identity.pub 227Contains the protocol version 1 RSA public key for authentication. 228The contents of this file should be added to 229.Pa $HOME/.ssh/authorized_keys 230on all machines 231where you wish to log in using RSA authentication. 232There is no need to keep the contents of this file secret. 233.It Pa $HOME/.ssh/id_dsa 234Contains the protocol version 2 DSA authentication identity of the user. 235This file should not be readable by anyone but the user. 236It is possible to 237specify a passphrase when generating the key; that passphrase will be 238used to encrypt the private part of this file using 3DES. 239This file is not automatically accessed by 240.Nm 241but it is offered as the default file for the private key. 242.Xr ssh 1 243will read this file when a login attempt is made. 244.It Pa $HOME/.ssh/id_dsa.pub 245Contains the protocol version 2 DSA public key for authentication. 246The contents of this file should be added to 247.Pa $HOME/.ssh/authorized_keys 248on all machines 249where you wish to log in using public key authentication. 250There is no need to keep the contents of this file secret. 251.It Pa $HOME/.ssh/id_rsa 252Contains the protocol version 2 RSA authentication identity of the user. 253This file should not be readable by anyone but the user. 254It is possible to 255specify a passphrase when generating the key; that passphrase will be 256used to encrypt the private part of this file using 3DES. 257This file is not automatically accessed by 258.Nm 259but it is offered as the default file for the private key. 260.Xr ssh 1 261will read this file when a login attempt is made. 262.It Pa $HOME/.ssh/id_rsa.pub 263Contains the protocol version 2 RSA public key for authentication. 264The contents of this file should be added to 265.Pa $HOME/.ssh/authorized_keys 266on all machines 267where you wish to log in using public key authentication. 268There is no need to keep the contents of this file secret. 269.El 270.Sh AUTHORS 271OpenSSH is a derivative of the original and free 272ssh 1.2.12 release by Tatu Ylonen. 273Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, 274Theo de Raadt and Dug Song 275removed many bugs, re-added newer features and 276created OpenSSH. 277Markus Friedl contributed the support for SSH 278protocol versions 1.5 and 2.0. 279.Sh SEE ALSO 280.Xr ssh 1 , 281.Xr ssh-add 1 , 282.Xr ssh-agent 1 , 283.Xr sshd 8 284.Rs 285.%A J. Galbraith 286.%A R. Thayer 287.%T "SECSH Public Key File Format" 288.%N draft-ietf-secsh-publickeyfile-01.txt 289.%D March 2001 290.%O work in progress material 291.Re 292