Annotation of src/usr.bin/ssh/ssh-keygen.1, Revision 1.67
1.67 ! dtucker 1: .\" $OpenBSD: ssh-keygen.1,v 1.66 2005/03/01 18:15:56 jmc Exp $
1.29 niklas 2: .\"
1.1 deraadt 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: .\"
1.22 deraadt 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: .\"
1.33 deraadt 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.
1.22 deraadt 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.
1.1 deraadt 28: .\"
1.22 deraadt 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.
1.1 deraadt 39: .\"
1.2 deraadt 40: .Dd September 25, 1999
41: .Dt SSH-KEYGEN 1
42: .Os
43: .Sh NAME
44: .Nm ssh-keygen
1.37 markus 45: .Nd authentication key generation, management and conversion
1.2 deraadt 46: .Sh SYNOPSIS
47: .Nm ssh-keygen
1.56 jmc 48: .Bk -words
1.25 markus 49: .Op Fl q
1.2 deraadt 50: .Op Fl b Ar bits
1.53 stevesk 51: .Fl t Ar type
1.2 deraadt 52: .Op Fl N Ar new_passphrase
53: .Op Fl C Ar comment
1.20 markus 54: .Op Fl f Ar output_keyfile
1.56 jmc 55: .Ek
1.2 deraadt 56: .Nm ssh-keygen
57: .Fl p
58: .Op Fl P Ar old_passphrase
59: .Op Fl N Ar new_passphrase
1.9 markus 60: .Op Fl f Ar keyfile
1.2 deraadt 61: .Nm ssh-keygen
1.37 markus 62: .Fl i
1.20 markus 63: .Op Fl f Ar input_keyfile
1.16 deraadt 64: .Nm ssh-keygen
1.37 markus 65: .Fl e
1.20 markus 66: .Op Fl f Ar input_keyfile
1.16 deraadt 67: .Nm ssh-keygen
1.17 markus 68: .Fl y
1.20 markus 69: .Op Fl f Ar input_keyfile
1.17 markus 70: .Nm ssh-keygen
1.2 deraadt 71: .Fl c
72: .Op Fl P Ar passphrase
73: .Op Fl C Ar comment
1.9 markus 74: .Op Fl f Ar keyfile
75: .Nm ssh-keygen
76: .Fl l
1.35 markus 77: .Op Fl f Ar input_keyfile
78: .Nm ssh-keygen
79: .Fl B
1.20 markus 80: .Op Fl f Ar input_keyfile
1.48 jakob 81: .Nm ssh-keygen
82: .Fl D Ar reader
83: .Nm ssh-keygen
1.64 djm 84: .Fl F Ar hostname
85: .Op Fl f Ar known_hosts_file
86: .Nm ssh-keygen
87: .Fl H
88: .Op Fl f Ar known_hosts_file
89: .Nm ssh-keygen
90: .Fl R Ar hostname
91: .Op Fl f Ar known_hosts_file
92: .Nm ssh-keygen
1.48 jakob 93: .Fl U Ar reader
94: .Op Fl f Ar input_keyfile
1.57 jakob 95: .Nm ssh-keygen
96: .Fl r Ar hostname
97: .Op Fl f Ar input_keyfile
98: .Op Fl g
1.60 djm 99: .Nm ssh-keygen
100: .Fl G Ar output_file
1.61 djm 101: .Op Fl v
1.60 djm 102: .Op Fl b Ar bits
103: .Op Fl M Ar memory
104: .Op Fl S Ar start_point
105: .Nm ssh-keygen
106: .Fl T Ar output_file
107: .Fl f Ar input_file
1.61 djm 108: .Op Fl v
1.60 djm 109: .Op Fl a Ar num_trials
110: .Op Fl W Ar generator
1.13 aaron 111: .Sh DESCRIPTION
1.2 deraadt 112: .Nm
1.37 markus 113: generates, manages and converts authentication keys for
1.2 deraadt 114: .Xr ssh 1 .
1.15 deraadt 115: .Nm
1.54 deraadt 116: can create RSA keys for use by SSH protocol version 1 and RSA or DSA
1.58 jmc 117: keys for use by SSH protocol version 2.
118: The type of key to be generated is specified with the
1.25 markus 119: .Fl t
1.52 djm 120: option.
1.15 deraadt 121: .Pp
1.60 djm 122: .Nm
123: is also used to generate groups for use in Diffie-Hellman group
124: exchange (DH-GEX).
125: See the
126: .Sx MODULI GENERATION
127: section for details.
128: .Pp
1.2 deraadt 129: Normally each user wishing to use SSH
1.15 deraadt 130: with RSA or DSA authentication runs this once to create the authentication
1.1 deraadt 131: key in
1.36 itojun 132: .Pa $HOME/.ssh/identity ,
133: .Pa $HOME/.ssh/id_dsa
1.15 deraadt 134: or
1.36 itojun 135: .Pa $HOME/.ssh/id_rsa .
1.15 deraadt 136: Additionally, the system administrator may use this to generate host keys,
137: as seen in
138: .Pa /etc/rc .
1.2 deraadt 139: .Pp
1.1 deraadt 140: Normally this program generates the key and asks for a file in which
1.12 aaron 141: to store the private key.
142: The public key is stored in a file with the same name but
1.2 deraadt 143: .Dq .pub
1.12 aaron 144: appended.
145: The program also asks for a passphrase.
146: The passphrase may be empty to indicate no passphrase
1.26 markus 147: (host keys must have an empty passphrase), or it may be a string of
1.12 aaron 148: arbitrary length.
1.51 stevesk 149: A passphrase is similar to a password, except it can be a phrase with a
150: series of words, punctuation, numbers, whitespace, or any string of
151: characters you want.
152: Good passphrases are 10-30 characters long, are
1.1 deraadt 153: not simple sentences or otherwise easily guessable (English
1.42 markus 154: prose has only 1-2 bits of entropy per character, and provides very bad
1.51 stevesk 155: passphrases), and contain a mix of upper and lowercase letters,
156: numbers, and non-alphanumeric characters.
1.12 aaron 157: The passphrase can be changed later by using the
1.2 deraadt 158: .Fl p
1.1 deraadt 159: option.
1.2 deraadt 160: .Pp
1.12 aaron 161: There is no way to recover a lost passphrase.
162: If the passphrase is
1.49 deraadt 163: lost or forgotten, a new key must be generated and copied to the
1.1 deraadt 164: corresponding public key to other machines.
1.2 deraadt 165: .Pp
1.37 markus 166: For RSA1 keys,
167: there is also a comment field in the key file that is only for
1.12 aaron 168: convenience to the user to help identify the key.
169: The comment can tell what the key is for, or whatever is useful.
170: The comment is initialized to
1.2 deraadt 171: .Dq user@host
172: when the key is created, but can be changed using the
173: .Fl c
1.1 deraadt 174: option.
1.2 deraadt 175: .Pp
1.15 deraadt 176: After a key is generated, instructions below detail where the keys
177: should be placed to be activated.
178: .Pp
1.2 deraadt 179: The options are as follows:
180: .Bl -tag -width Ds
1.60 djm 181: .It Fl a Ar trials
182: Specifies the number of primality tests to perform when screening DH-GEX
183: candidates using the
184: .Fl T
185: command.
1.66 jmc 186: .It Fl B
187: Show the bubblebabble digest of specified private or public key file.
1.2 deraadt 188: .It Fl b Ar bits
1.12 aaron 189: Specifies the number of bits in the key to create.
190: Minimum is 512 bits.
1.55 stevesk 191: Generally, 1024 bits is considered sufficient.
1.12 aaron 192: The default is 1024 bits.
1.66 jmc 193: .It Fl C Ar comment
194: Provides a new comment.
1.2 deraadt 195: .It Fl c
1.1 deraadt 196: Requests changing the comment in the private and public key files.
1.50 markus 197: This operation is only supported for RSA1 keys.
1.1 deraadt 198: The program will prompt for the file containing the private keys, for
1.41 stevesk 199: the passphrase if the key has one, and for the new comment.
1.66 jmc 200: .It Fl D Ar reader
201: Download the RSA public key stored in the smartcard in
202: .Ar reader .
1.37 markus 203: .It Fl e
1.40 markus 204: This option will read a private or public OpenSSH key file and
205: print the key in a
1.37 markus 206: .Sq SECSH Public Key File Format
207: to stdout.
208: This option allows exporting keys for use by several commercial
209: SSH implementations.
1.66 jmc 210: .It Fl F Ar hostname
211: Search for the specified
212: .Ar hostname
213: in a
214: .Pa known_hosts
215: file, listing any occurrences found.
216: This option is useful to find hashed host names or addresses and may also be
217: used in conjunction with the
218: .Fl H
219: option to print found keys in a hashed format.
220: .It Fl f Ar filename
221: Specifies the filename of the key file.
222: .It Fl G Ar output_file
223: Generate candidate primes for DH-GEX.
224: These primes must be screened for
225: safety (using the
226: .Fl T
227: option) before use.
1.57 jakob 228: .It Fl g
1.62 jakob 229: Use generic DNS format when printing fingerprint resource records using the
1.63 jmc 230: .Fl r
1.62 jakob 231: command.
1.66 jmc 232: .It Fl H
233: Hash a
234: .Pa known_hosts
1.67 ! dtucker 235: file.
! 236: This replaces all hostnames and addresses with hashed representations
! 237: within the specified file; the original content is moved to a file with
! 238: a .old suffix.
1.66 jmc 239: These hashes may be used normally by
240: .Nm ssh
241: and
242: .Nm sshd ,
243: but they do not reveal identifying information should the file's contents
244: be disclosed.
245: This option will not modify existing hashed hostnames and is therefore safe
246: to use on files that mix hashed and non-hashed names.
1.37 markus 247: .It Fl i
248: This option will read an unencrypted private (or public) key file
249: in SSH2-compatible format and print an OpenSSH compatible private
250: (or public) key to stdout.
251: .Nm
1.38 markus 252: also reads the
1.37 markus 253: .Sq SECSH Public Key File Format .
254: This option allows importing keys from several commercial
255: SSH implementations.
1.9 markus 256: .It Fl l
1.50 markus 257: Show fingerprint of specified public key file.
258: Private RSA1 keys are also supported.
259: For RSA and DSA keys
260: .Nm
261: tries to find the matching public key file and prints its fingerprint.
1.66 jmc 262: .It Fl M Ar memory
263: Specify the amount of memory to use (in megabytes) when generating
264: candidate moduli for DH-GEX.
265: .It Fl N Ar new_passphrase
266: Provides the new passphrase.
267: .It Fl P Ar passphrase
268: Provides the (old) passphrase.
1.2 deraadt 269: .It Fl p
1.1 deraadt 270: Requests changing the passphrase of a private key file instead of
1.12 aaron 271: creating a new private key.
272: The program will prompt for the file
1.1 deraadt 273: containing the private key, for the old passphrase, and twice for the
274: new passphrase.
1.5 aaron 275: .It Fl q
276: Silence
277: .Nm ssh-keygen .
278: Used by
279: .Pa /etc/rc
280: when creating a new key.
1.64 djm 281: .It Fl R Ar hostname
282: Removes all keys belonging to
283: .Ar hostname
1.65 jmc 284: from a
1.64 djm 285: .Pa known_hosts
286: file.
1.65 jmc 287: This option is useful to delete hashed hosts (see the
1.64 djm 288: .Fl H
289: option above).
1.66 jmc 290: .It Fl r Ar hostname
291: Print the SSHFP fingerprint resource record named
292: .Ar hostname
293: for the specified public key file.
1.60 djm 294: .It Fl S Ar start
295: Specify start point (in hex) when generating candidate moduli for DH-GEX.
296: .It Fl T Ar output_file
297: Test DH group exchange candidate primes (generated using the
298: .Fl G
299: option) for safety.
1.66 jmc 300: .It Fl t Ar type
301: Specifies the type of key to create.
302: The possible values are
303: .Dq rsa1
304: for protocol version 1 and
305: .Dq rsa
306: or
307: .Dq dsa
308: for protocol version 2.
1.48 jakob 309: .It Fl U Ar reader
310: Upload an existing RSA private key into the smartcard in
311: .Ar reader .
1.61 djm 312: .It Fl v
313: Verbose mode.
314: Causes
315: .Nm
316: to print debugging messages about its progress.
317: This is helpful for debugging moduli generation.
318: Multiple
319: .Fl v
320: options increase the verbosity.
321: The maximum is 3.
1.66 jmc 322: .It Fl W Ar generator
323: Specify desired generator when testing candidate moduli for DH-GEX.
324: .It Fl y
325: This option will read a private
326: OpenSSH format file and print an OpenSSH public key to stdout.
1.2 deraadt 327: .El
1.60 djm 328: .Sh MODULI GENERATION
329: .Nm
330: may be used to generate groups for the Diffie-Hellman Group Exchange
331: (DH-GEX) protocol.
332: Generating these groups is a two-step process: first, candidate
333: primes are generated using a fast, but memory intensive process.
334: These candidate primes are then tested for suitability (a CPU-intensive
335: process).
336: .Pp
337: Generation of primes is performed using the
338: .Fl G
339: option.
340: The desired length of the primes may be specified by the
341: .Fl b
342: option.
343: For example:
344: .Pp
1.66 jmc 345: .Dl # ssh-keygen -G moduli-2048.candidates -b 2048
1.60 djm 346: .Pp
347: By default, the search for primes begins at a random point in the
348: desired length range.
349: This may be overridden using the
350: .Fl S
351: option, which specifies a different start point (in hex).
352: .Pp
353: Once a set of candidates have been generated, they must be tested for
354: suitability.
355: This may be performed using the
356: .Fl T
357: option.
358: In this mode
359: .Nm
360: will read candidates from standard input (or a file specified using the
361: .Fl f
362: option).
363: For example:
364: .Pp
1.66 jmc 365: .Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates
1.60 djm 366: .Pp
367: By default, each candidate will be subjected to 100 primality tests.
368: This may be overridden using the
369: .Fl a
370: option.
371: The DH generator value will be chosen automatically for the
372: prime under consideration.
373: If a specific generator is desired, it may be requested using the
374: .Fl W
375: option.
1.66 jmc 376: Valid generator values are 2, 3, and 5.
1.60 djm 377: .Pp
378: Screened DH groups may be installed in
379: .Pa /etc/moduli .
380: It is important that this file contains moduli of a range of bit lengths and
381: that both ends of a connection share common moduli.
1.2 deraadt 382: .Sh FILES
383: .Bl -tag -width Ds
384: .It Pa $HOME/.ssh/identity
1.36 itojun 385: Contains the protocol version 1 RSA authentication identity of the user.
1.12 aaron 386: This file should not be readable by anyone but the user.
387: It is possible to
1.1 deraadt 388: specify a passphrase when generating the key; that passphrase will be
1.12 aaron 389: used to encrypt the private part of this file using 3DES.
390: This file is not automatically accessed by
1.2 deraadt 391: .Nm
1.1 deraadt 392: but it is offered as the default file for the private key.
1.46 markus 393: .Xr ssh 1
1.15 deraadt 394: will read this file when a login attempt is made.
1.2 deraadt 395: .It Pa $HOME/.ssh/identity.pub
1.36 itojun 396: Contains the protocol version 1 RSA public key for authentication.
1.12 aaron 397: The contents of this file should be added to
1.2 deraadt 398: .Pa $HOME/.ssh/authorized_keys
399: on all machines
1.49 deraadt 400: where the user wishes to log in using RSA authentication.
1.15 deraadt 401: There is no need to keep the contents of this file secret.
402: .It Pa $HOME/.ssh/id_dsa
1.36 itojun 403: Contains the protocol version 2 DSA authentication identity of the user.
1.15 deraadt 404: This file should not be readable by anyone but the user.
405: It is possible to
406: specify a passphrase when generating the key; that passphrase will be
407: used to encrypt the private part of this file using 3DES.
408: This file is not automatically accessed by
409: .Nm
410: but it is offered as the default file for the private key.
1.46 markus 411: .Xr ssh 1
1.15 deraadt 412: will read this file when a login attempt is made.
413: .It Pa $HOME/.ssh/id_dsa.pub
1.36 itojun 414: Contains the protocol version 2 DSA public key for authentication.
415: The contents of this file should be added to
1.43 markus 416: .Pa $HOME/.ssh/authorized_keys
1.36 itojun 417: on all machines
1.49 deraadt 418: where the user wishes to log in using public key authentication.
1.36 itojun 419: There is no need to keep the contents of this file secret.
420: .It Pa $HOME/.ssh/id_rsa
421: Contains the protocol version 2 RSA authentication identity of the user.
422: This file should not be readable by anyone but the user.
423: It is possible to
424: specify a passphrase when generating the key; that passphrase will be
425: used to encrypt the private part of this file using 3DES.
426: This file is not automatically accessed by
427: .Nm
428: but it is offered as the default file for the private key.
1.46 markus 429: .Xr ssh 1
1.36 itojun 430: will read this file when a login attempt is made.
431: .It Pa $HOME/.ssh/id_rsa.pub
432: Contains the protocol version 2 RSA public key for authentication.
1.15 deraadt 433: The contents of this file should be added to
1.43 markus 434: .Pa $HOME/.ssh/authorized_keys
1.15 deraadt 435: on all machines
1.49 deraadt 436: where the user wishes to log in using public key authentication.
1.12 aaron 437: There is no need to keep the contents of this file secret.
1.60 djm 438: .It Pa /etc/moduli
439: Contains Diffie-Hellman groups used for DH-GEX.
440: The file format is described in
441: .Xr moduli 5 .
1.19 aaron 442: .El
1.2 deraadt 443: .Sh SEE ALSO
444: .Xr ssh 1 ,
445: .Xr ssh-add 1 ,
1.8 ericj 446: .Xr ssh-agent 1 ,
1.60 djm 447: .Xr moduli 5 ,
1.30 itojun 448: .Xr sshd 8
1.37 markus 449: .Rs
1.45 deraadt 450: .%A J. Galbraith
451: .%A R. Thayer
1.37 markus 452: .%T "SECSH Public Key File Format"
453: .%N draft-ietf-secsh-publickeyfile-01.txt
454: .%D March 2001
455: .%O work in progress material
456: .Re
1.59 jmc 457: .Sh AUTHORS
458: OpenSSH is a derivative of the original and free
459: ssh 1.2.12 release by Tatu Ylonen.
460: Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
461: Theo de Raadt and Dug Song
462: removed many bugs, re-added newer features and
463: created OpenSSH.
464: Markus Friedl contributed the support for SSH
465: protocol versions 1.5 and 2.0.
![[BACK]](/icons/back.gif){kind=icon}
Return to ssh-keygen.1 CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh