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SSH-KEYGEN(1)		  BSD General Commands Manual		 SSH-KEYGEN(1)

     ssh-keygen	-- authentication key generation, management and conversion

     ssh-keygen	[-q] [-b bits] [-t dsa | ecdsa | ed25519 | rsa]
		[-N new_passphrase] [-C	comment] [-f output_keyfile]
     ssh-keygen	-p [-P old_passphrase] [-N new_passphrase] [-f keyfile]
     ssh-keygen	-i [-m key_format] [-f input_keyfile]
     ssh-keygen	-e [-m key_format] [-f input_keyfile]
     ssh-keygen	-y [-f input_keyfile]
     ssh-keygen	-c [-P passphrase] [-C comment]	[-f keyfile]
     ssh-keygen	-l [-v]	[-E fingerprint_hash] [-f input_keyfile]
     ssh-keygen	-B [-f input_keyfile]
     ssh-keygen	-D pkcs11
     ssh-keygen	-F hostname [-f	known_hosts_file] [-l]
     ssh-keygen	-H [-f known_hosts_file]
     ssh-keygen	-R hostname [-f	known_hosts_file]
     ssh-keygen	-r hostname [-f	input_keyfile] [-g]
     ssh-keygen	-G output_file [-v] [-b	bits] [-M memory] [-S start_point]
     ssh-keygen	-T output_file -f input_file [-v] [-a rounds] [-J num_lines]
		[-j start_line]	[-K checkpt] [-W generator]
     ssh-keygen	-s ca_key -I certificate_identity [-h] [-U]
		[-D pkcs11_provider] [-n principals] [-O option]
		[-V validity_interval] [-z serial_number] file ...
     ssh-keygen	-L [-f input_keyfile]
     ssh-keygen	-A [-f prefix_path]
     ssh-keygen	-k -f krl_file [-u] [-s	ca_public] [-z version_number]
		file ...
     ssh-keygen	-Q -f krl_file file ...

     ssh-keygen	generates, manages and converts	authentication keys for
     ssh(1).  ssh-keygen can create keys for use by SSH	protocol version 2.

     The type of key to	be generated is	specified with the -t option.  If in-
     voked without any arguments, ssh-keygen will generate an RSA key.

     ssh-keygen	is also	used to	generate groups	for use	in Diffie-Hellman
     group exchange (DH-GEX).  See the MODULI GENERATION section for details.

     Finally, ssh-keygen can be	used to	generate and update Key	Revocation
     Lists, and	to test	whether	given keys have	been revoked by	one.  See the
     KEY REVOCATION LISTS section for details.

     Normally each user	wishing	to use SSH with	public key authentication runs
     this once to create the authentication key	in ~/.ssh/id_dsa,
     ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519	or ~/.ssh/id_rsa.  Additionally, the
     system administrator may use this to generate host	keys, as seen in

     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 ".pub" appended.	The program also asks for a passphrase.	 The
     passphrase	may be empty to	indicate no passphrase (host keys must have an
     empty passphrase),	or it may be a string of arbitrary length.  A
     passphrase	is similar to a	password, except it can	be a phrase with a se-
     ries of words, punctuation, numbers, whitespace, or any string of charac-
     ters you want.  Good passphrases are 10-30	characters long, are not sim-
     ple sentences or otherwise	easily guessable (English prose	has only 1-2
     bits of entropy per character, and	provides very bad passphrases),	and
     contain a mix of upper and	lowercase letters, numbers, and	non-alphanu-
     meric characters.	The passphrase can be changed later by using the -p

     There is no way to	recover	a lost passphrase.  If the passphrase is lost
     or	forgotten, a new key must be generated and the corresponding public
     key copied	to other machines.

     For keys stored in	the newer OpenSSH format, 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 "user@host" when	the key	is
     created, but can be changed using the -c option.

     After a key is generated, instructions below detail where the keys	should
     be	placed to be activated.

     The options are as	follows:

     -A	     For each of the key types (rsa, dsa, ecdsa	and ed25519) for which
	     host keys do not exist, generate the host keys with the default
	     key file path, an empty passphrase, default bits for the key
	     type, and default comment.	 If -f has also	been specified,	its
	     argument is used as a prefix to the default path for the result-
	     ing host key files.  This is used by /etc/rc to generate new host

     -a	rounds
	     When saving a private key this option specifies the number	of KDF
	     (key derivation function) rounds used.  Higher numbers result in
	     slower passphrase verification and	increased resistance to	brute-
	     force password cracking (should the keys be stolen).

	     When screening DH-GEX candidates (using the -T command).  This
	     option specifies the number of primality tests to perform.

     -B	     Show the bubblebabble digest of specified private or public key

     -b	bits
	     Specifies the number of bits in the key to	create.	 For RSA keys,
	     the minimum size is 1024 bits and the default is 2048 bits.  Gen-
	     erally, 2048 bits is considered sufficient.  DSA keys must	be ex-
	     actly 1024	bits as	specified by FIPS 186-2.  For ECDSA keys, the
	     -b	flag determines	the key	length by selecting from one of	three
	     elliptic curve sizes: 256,	384 or 521 bits.  Attempting to	use
	     bit lengths other than these three	values for ECDSA keys will
	     fail.  Ed25519 keys have a	fixed length and the -b	flag will be

     -C	comment
	     Provides a	new comment.

     -c	     Requests changing the comment in the private and public key
	     files.  The program will prompt for the file containing the pri-
	     vate keys,	for the	passphrase if the key has one, and for the new

     -D	pkcs11
	     Download the RSA public keys provided by the PKCS#11 shared li-
	     brary pkcs11.  When used in combination with -s, this option in-
	     dicates that a CA key resides in a	PKCS#11	token (see the
	     CERTIFICATES section for details).

     -E	fingerprint_hash
	     Specifies the hash	algorithm used when displaying key finger-
	     prints.  Valid options are: "md5" and "sha256".  The default is

     -e	     This option will read a private or	public OpenSSH key file	and
	     print to stdout the key in	one of the formats specified by	the -m
	     option.  The default export format	is "RFC4716".  This option al-
	     lows exporting OpenSSH keys for use by other programs, including
	     several commercial	SSH implementations.

     -F	hostname
	     Search for	the specified hostname in a known_hosts	file, listing
	     any occurrences found.  This option is useful to find hashed host
	     names or addresses	and may	also be	used in	conjunction with the
	     -H	option to print	found keys in a	hashed format.

     -f	filename
	     Specifies the filename of the key file.

     -G	output_file
	     Generate candidate	primes for DH-GEX.  These primes must be
	     screened for safety (using	the -T option) before use.

     -g	     Use generic DNS format when printing fingerprint resource records
	     using the -r command.

     -H	     Hash a known_hosts	file.  This replaces all hostnames and ad-
	     dresses with hashed representations within	the specified file;
	     the original content is moved to a	file with a .old suffix.
	     These hashes may be used normally by ssh and sshd,	but they do
	     not reveal	identifying information	should the file's contents be
	     disclosed.	 This option will not modify existing hashed hostnames
	     and is therefore safe to use on files that	mix hashed and non-
	     hashed names.

     -h	     When signing a key, create	a host certificate instead of a	user
	     certificate.  Please see the CERTIFICATES section for details.

     -I	certificate_identity
	     Specify the key identity when signing a public key.  Please see
	     the CERTIFICATES section for details.

     -i	     This option will read an unencrypted private (or public) key file
	     in	the format specified by	the -m option and print	an OpenSSH
	     compatible	private	(or public) key	to stdout.  This option	allows
	     importing keys from other software, including several commercial
	     SSH implementations.  The default import format is	"RFC4716".

     -J	num_lines
	     Exit after	screening the specified	number of lines	while perform-
	     ing DH candidate screening	using the -T option.

     -j	start_line
	     Start screening at	the specified line number while	performing DH
	     candidate screening using the -T option.

     -K	checkpt
	     Write the last line processed to the file checkpt while perform-
	     ing DH candidate screening	using the -T option.  This will	be
	     used to skip lines	in the input file that have already been pro-
	     cessed if the job is restarted.

     -k	     Generate a	KRL file.  In this mode, ssh-keygen will generate a
	     KRL file at the location specified	via the	-f flag	that revokes
	     every key or certificate presented	on the command line.
	     Keys/certificates to be revoked may be specified by public	key
	     file or using the format described	in the KEY REVOCATION LISTS

     -L	     Prints the	contents of one	or more	certificates.

     -l	     Show fingerprint of specified public key file.  For RSA and DSA
	     keys ssh-keygen tries to find the matching	public key file	and
	     prints its	fingerprint.  If combined with -v, a visual ASCII art
	     representation of the key is supplied with	the fingerprint.

     -M	memory
	     Specify the amount	of memory to use (in megabytes)	when generat-
	     ing candidate moduli for DH-GEX.

     -m	key_format
	     Specify a key format for the -i (import) or -e (export) conver-
	     sion options.  The	supported key formats are: "RFC4716" (RFC
	     4716/SSH2 public or private key), "PKCS8" (PEM PKCS8 public key)
	     or	"PEM" (PEM public key).	 The default conversion	format is
	     "RFC4716".	 Setting a format of "PEM" when	generating or updating
	     a supported private key type will cause the key to	be stored in
	     the legacy	PEM private key	format.

     -N	new_passphrase
	     Provides the new passphrase.

     -n	principals
	     Specify one or more principals (user or host names) to be in-
	     cluded in a certificate when signing a key.  Multiple principals
	     may be specified, separated by commas.  Please see	the
	     CERTIFICATES section for details.

     -O	option
	     Specify a certificate option when signing a key.  This option may
	     be	specified multiple times.  See also the	CERTIFICATES section
	     for further details.

	     At	present, no standard options are valid for host	keys.  The op-
	     tions that	are valid for user certificates	are:

	     clear   Clear all enabled permissions.  This is useful for	clear-
		     ing the default set of permissions	so permissions may be
		     added individually.

		     Includes an arbitrary certificate critical	option or ex-
		     tension.  The specified name should include a domain suf-
		     fix, e.g. "".  If contents	is specified
		     then it is	included as the	contents of the	extension/op-
		     tion encoded as a string, otherwise the extension/option
		     is	created	with no	contents (usually indicating a flag).
		     Extensions	may be ignored by a client or server that does
		     not recognise them, whereas unknown critical options will
		     cause the certificate to be refused.

		     Forces the	execution of command instead of	any shell or
		     command specified by the user when	the certificate	is
		     used for authentication.

		     Disable ssh-agent(1) forwarding (permitted	by default).

		     Disable port forwarding (permitted	by default).

	     no-pty  Disable PTY allocation (permitted by default).

		     Disable execution of ~/.ssh/rc by sshd(8) (permitted by

		     Disable X11 forwarding (permitted by default).

		     Allows ssh-agent(1) forwarding.

		     Allows port forwarding.

		     Allows PTY	allocation.

		     Allows execution of ~/.ssh/rc by sshd(8).

		     Allows X11	forwarding.

		     Restrict the source addresses from	which the certificate
		     is	considered valid.  The address_list is a comma-sepa-
		     rated list	of one or more address/netmask pairs in	CIDR

     -P	passphrase
	     Provides the (old)	passphrase.

     -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.

     -Q	     Test whether keys have been revoked in a KRL.

     -q	     Silence ssh-keygen.

     -R	hostname
	     Removes all keys belonging	to hostname from a known_hosts file.
	     This option is useful to delete hashed hosts (see the -H option

     -r	hostname
	     Print the SSHFP fingerprint resource record named hostname	for
	     the specified public key file.

     -S	start
	     Specify start point (in hex) when generating candidate moduli for

     -s	ca_key
	     Certify (sign) a public key using the specified CA	key.  Please
	     see the CERTIFICATES section for details.

	     When generating a KRL, -s specifies a path	to a CA	public key
	     file used to revoke certificates directly by key ID or serial
	     number.  See the KEY REVOCATION LISTS section for details.

     -T	output_file
	     Test DH group exchange candidate primes (generated	using the -G
	     option) for safety.

     -t	dsa | ecdsa | ed25519 |	rsa
	     Specifies the type	of key to create.  The possible	values are
	     "dsa", "ecdsa", "ed25519",	or "rsa".

     -U	     When used in combination with -s, this option indicates that a CA
	     key resides in a ssh-agent(1).  See the CERTIFICATES section for
	     more information.

     -u	     Update a KRL.  When specified with	-k, keys listed	via the	com-
	     mand line are added to the	existing KRL rather than a new KRL be-
	     ing created.

     -V	validity_interval
	     Specify a validity	interval when signing a	certificate.  A	valid-
	     ity interval may consist of a single time,	indicating that	the
	     certificate is valid beginning now	and expiring at	that time, or
	     may consist of two	times separated	by a colon to indicate an ex-
	     plicit time interval.

	     The start time may	be specified as	the string "always" to indi-
	     cate the certificate has no specified start time, a date in
	     YYYYMMDD format, a	time in	YYYYMMDDHHMM[SS] format, a relative
	     time (to the current time)	consisting of a	minus sign followed by
	     an	interval in the	format described in the	TIME FORMATS section
	     of	sshd_config(5).

	     The end time may be specified as a	YYYYMMDD date, a YYYYMMD-
	     DHHMM[SS] time, a relative	time starting with a plus character or
	     the string	"forever" to indicate that the certificate has no ex-
	     pirty date.

	     For example: "+52w1d" (valid from now to 52 weeks and one day
	     from now),	"-4w:+4w" (valid from four weeks ago to	four weeks
	     from now),	"20100101123000:20110101123000"	(valid from 12:30 PM,
	     January 1st, 2010 to 12:30	PM, January 1st, 2011),	"-1d:20110101"
	     (valid from yesterday to midnight,	January	1st, 2011).
	     "-1m:forever" (valid from one minute ago and never	expiring).

     -v	     Verbose mode.  Causes ssh-keygen to print debugging messages
	     about its progress.  This is helpful for debugging	moduli genera-
	     tion.  Multiple -v	options	increase the verbosity.	 The maximum
	     is	3.

     -W	generator
	     Specify desired generator when testing candidate moduli for DH-

     -y	     This option will read a private OpenSSH format file and print an
	     OpenSSH public key	to stdout.

     -z	serial_number
	     Specifies a serial	number to be embedded in the certificate to
	     distinguish this certificate from others from the same CA.	 The
	     default serial number is zero.

	     When generating a KRL, the	-z flag	is used	to specify a KRL ver-
	     sion number.

     ssh-keygen	may be used to generate	groups for the Diffie-Hellman Group
     Exchange (DH-GEX) protocol.  Generating these groups is a two-step
     process: first, candidate primes are generated using a fast, but memory
     intensive process.	 These candidate primes	are then tested	for suitabil-
     ity (a CPU-intensive process).

     Generation	of primes is performed using the -G option.  The desired
     length of the primes may be specified by the -b option.  For example:

	   # ssh-keygen	-G moduli-2048.candidates -b 2048

     By	default, the search for	primes begins at a random point	in the desired
     length range.  This may be	overridden using the -S	option,	which speci-
     fies a different start point (in hex).

     Once a set	of candidates have been	generated, they	must be	screened for
     suitability.  This	may be performed using the -T option.  In this mode
     ssh-keygen	will read candidates from standard input (or a file specified
     using the -f option).  For	example:

	   # ssh-keygen	-T moduli-2048 -f moduli-2048.candidates

     By	default, each candidate	will be	subjected to 100 primality tests.
     This may be overridden using the -a option.  The DH generator value will
     be	chosen automatically for the prime under consideration.	 If a specific
     generator is desired, it may be requested using the -W option.  Valid
     generator values are 2, 3,	and 5.

     Screened DH groups	may be installed in /etc/moduli.  It is	important that
     this file contains	moduli of a range of bit lengths and that both ends of
     a connection share	common moduli.

     ssh-keygen	supports signing of keys to produce certificates that may be
     used for user or host authentication.  Certificates consist of a public
     key, some identity	information, zero or more principal (user or host)
     names and a set of	options	that are signed	by a Certification Authority
     (CA) key.	Clients	or servers may then trust only the CA key and verify
     its signature on a	certificate rather than	trusting many user/host	keys.
     Note that OpenSSH certificates are	a different, and much simpler, format
     to	the X.509 certificates used in ssl(8).

     ssh-keygen	supports two types of certificates: user and host.  User cer-
     tificates authenticate users to servers, whereas host certificates	au-
     thenticate	server hosts to	users.	To generate a user certificate:

	   $ ssh-keygen	-s /path/to/ca_key -I key_id /path/to/

     The resultant certificate will be placed in /path/to/
     A host certificate	requires the -h	option:

	   $ ssh-keygen	-s /path/to/ca_key -I key_id -h	/path/to/

     The host certificate will be output to /path/to/

     It	is possible to sign using a CA key stored in a PKCS#11 token by	pro-
     viding the	token library using -D and identifying the CA key by providing
     its public	half as	an argument to -s:

	   $ ssh-keygen	-s -D -I key_id

     Similarly,	it is possible for the CA key to be hosted in a	ssh-agent(1).
     This is indicated by the -U flag and, again, the CA key must be identi-
     fied by its public	half.

	   $ ssh-keygen	-Us -I key_id

     In	all cases, key_id is a "key identifier"	that is	logged by the server
     when the certificate is used for authentication.

     Certificates may be limited to be valid for a set of principal
     (user/host) names.	 By default, generated certificates are	valid for all
     users or hosts.  To generate a certificate	for a specified	set of princi-

	   $ ssh-keygen	-s ca_key -I key_id -n user1,user2
	   $ ssh-keygen	-s ca_key -I key_id -h -n host.domain

     Additional	limitations on the validity and	use of user certificates may
     be	specified through certificate options.	A certificate option may dis-
     able features of the SSH session, may be valid only when presented	from
     particular	source addresses or may	force the use of a specific command.
     For a list	of valid certificate options, see the documentation for	the -O
     option above.

     Finally, certificates may be defined with a validity lifetime.  The -V
     option allows specification of certificate	start and end times.  A	cer-
     tificate that is presented	at a time outside this range will not be con-
     sidered valid.  By	default, certificates are valid	from UNIX Epoch	to the
     distant future.

     For certificates to be used for user or host authentication, the CA pub-
     lic key must be trusted by	sshd(8)	or ssh(1).  Please refer to those man-
     ual pages for details.

     ssh-keygen	is able	to manage OpenSSH format Key Revocation	Lists (KRLs).
     These binary files	specify	keys or	certificates to	be revoked using a
     compact format, taking as little as one bit per certificate if they are
     being revoked by serial number.

     KRLs may be generated using the -k	flag.  This option reads one or	more
     files from	the command line and generates a new KRL.  The files may ei-
     ther contain a KRL	specification (see below) or public keys, listed one
     per line.	Plain public keys are revoked by listing their hash or con-
     tents in the KRL and certificates revoked by serial number	or key ID (if
     the serial	is zero	or not available).

     Revoking keys using a KRL specification offers explicit control over the
     types of record used to revoke keys and may be used to directly revoke
     certificates by serial number or key ID without having the	complete orig-
     inal certificate on hand.	A KRL specification consists of	lines contain-
     ing one of	the following directives followed by a colon and some direc-
     tive-specific information.

     serial: serial_number[-serial_number]
	     Revokes a certificate with	the specified serial number.  Serial
	     numbers are 64-bit	values,	not including zero and may be ex-
	     pressed in	decimal, hex or	octal.	If two serial numbers are
	     specified separated by a hyphen, then the range of	serial numbers
	     including and between each	is revoked.  The CA key	must have been
	     specified on the ssh-keygen command line using the	-s option.

     id: key_id
	     Revokes a certificate with	the specified key ID string.  The CA
	     key must have been	specified on the ssh-keygen command line using
	     the -s option.

     key: public_key
	     Revokes the specified key.	 If a certificate is listed, then it
	     is	revoked	as a plain public key.

     sha1: public_key
	     Revokes the specified key by including its	SHA1 hash in the KRL.

     sha256: public_key
	     Revokes the specified key by including its	SHA256 hash in the
	     KRL.  KRLs	that revoke keys by SHA256 hash	are not	supported by
	     OpenSSH versions prior to 7.9.

     hash: fingerprint
	     Revokes a key using a fingerprint hash, as	obtained from a
	     sshd(8) authentication log	message	or the ssh-keygen -l flag.
	     Only SHA256 fingerprints are supported here and resultant KRLs
	     are not supported by OpenSSH versions prior to 7.9.

     KRLs may be updated using the -u flag in addition to -k.  When this op-
     tion is specified,	keys listed via	the command line are merged into the
     KRL, adding to those already there.

     It	is also	possible, given	a KRL, to test whether it revokes a particular
     key (or keys).  The -Q flag will query an existing	KRL, testing each key
     specified on the command line.  If	any key	listed on the command line has
     been revoked (or an error encountered) then ssh-keygen will exit with a
     non-zero exit status.  A zero exit	status will only be returned if	no key
     was revoked.

	     Contains the DSA, ECDSA, Ed25519 or 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 128-bit AES.  This	file is	not automatically ac-
	     cessed by ssh-keygen but it is offered as the default file	for
	     the private key.  ssh(1) will read	this file when a login attempt
	     is	made.

	     Contains the DSA, ECDSA, Ed25519 or RSA public key	for authenti-
	     cation.  The contents of this file	should be added	to
	     ~/.ssh/authorized_keys on all machines where the user wishes to
	     log in using public key authentication.  There is no need to keep
	     the contents of this file secret.

	     Contains Diffie-Hellman groups used for DH-GEX.  The file format
	     is	described in moduli(5).

     ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8)

     The Secure	Shell (SSH) Public Key File Format, RFC	4716, 2006.

     OpenSSH is	a derivative of	the original and free ssh 1.2.12 release by
     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
     de	Raadt and Dug Song removed many	bugs, re-added newer features and cre-
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.

BSD			      September	12, 2018			   BSD


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