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                    [-f output_keyfile]
         ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile]
         ssh-keygen -i [-f input_keyfile]
         ssh-keygen -e [-f input_keyfile]
         ssh-keygen -y [-f input_keyfile]
         ssh-keygen -c [-P passphrase] [-C comment] [-f keyfile]
         ssh-keygen -l [-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 num_trials]
                    [-W generator]
         ssh-keygen [-n] [-D smartcard]
         ssh-keygen -s ca_key -I certificate_identity [-h] [-Z principals]
                    [-O option] [-V validity_interval] [-z serial_number] file ...
         ssh-keygen -L [-f input_keyfile]


         ssh-keygen generates, manages and converts authentication keys for
         ssh(1).  ssh-keygen can create RSA keys for use by SSH protocol version 1
         and DSA, ECDSA or RSA keys for use by SSH protocol version 2.  The type
         of key to be generated is specified with the -t option.  If invoked with-
         out any arguments, ssh-keygen will generate an RSA key for use in SSH
         protocol 2 connections.
         ssh-keygen is also used to generate groups for use in Diffie-Hellman
         group exchange (DH-GEX).  See the MODULI GENERATION section for details.
         Normally each user wishing to use SSH with public key authentication runs
         this once to create the authentication key in ~/.ssh/identity,
         ~/.ssh/id_ecdsa, ~/.ssh/id_dsa or ~/.ssh/id_rsa.  Additionally, the sys-
         tem administrator may use this to generate host keys, as seen in /etc/rc.
         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
         series of words, punctuation, numbers, whitespace, or any string of char-
         acters you want.  Good passphrases are 10-30 characters long, are not
         simple 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-
         alphanumeric characters.  The passphrase can be changed later by using
         the -p option.
         There is no way to recover a lost passphrase.  If the passphrase is lost
         -a trials
                 Specifies the number of primality tests to perform when screening
                 DH-GEX candidates using the -T command.
         -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 768 bits and the default is 2048 bits.  Gen-
                 erally, 2048 bits is considered sufficient.  DSA keys must be
                 exactly 1024 bits as specified by FIPS 186-2.
         -C comment
                 Provides a new comment.
         -c      Requests changing the comment in the private and public key
                 files.  This operation is only supported for RSA1 keys.  The pro-
                 gram will prompt for the file containing the private keys, for
                 the passphrase if the key has one, and for the new comment.
         -D pkcs11
                 Download the RSA public keys stored in the pkcs11 provider.
         -e      This option will read a private or public OpenSSH key file and
                 print the key in RFC 4716 SSH Public Key File Format to stdout.
                 This option allows exporting keys for use by 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
                 addresses 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-
         -L      Prints the contents of a certificate.
         -l      Show fingerprint of specified public key file.  Private RSA1 keys
                 are also supported.  For RSA and DSA keys ssh-keygen tries to
                 find the matching public key file and prints its fingerprint.  If
                 combined with -v, an ASCII art representation of the key is sup-
                 plied with the fingerprint.
         -M memory
                 Specify the amount of memory to use (in megabytes) when generat-
                 ing candidate moduli for DH-GEX.
         -n      Extract the public key from smartcard.
         -N new_passphrase
                 Provides the new passphrase.
         -Z principals
                 Specify one or more principals (user or host names) to be
                 included in a certificate when signing a key.  Multiple princi-
                 pals 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.  Please see the CERTIFICATES section
                 for details.  The options that are valid for user certificates
                         Disable X11 forwarding. (permitted by default)
                         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
                 clear   Clear all enabled permissions.  This is useful for clear-
                         ing the default set of permissions so permissions may be
                         added individually.
                         Allows X11 forwarding.
                         used for authentication.
                         Restrict the source addresses from which the certificate
                         is considered valid from.  The address_list is a comma-
                         separated list of one or more address/netmask pairs in
                         CIDR format.
                 At present, no options are valid for host keys.
         -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      Silence ssh-keygen.  Used by /etc/rc when creating a new key.
         -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.
         -T output_file
                 Test DH group exchange candidate primes (generated using the -G
                 option) for safety.
         -t type
                 Specifies the type of key to create.  The possible values are
                 "rsa1" for protocol version 1 and "dsa", "ecdsa" or "rsa" for
                 protocol version 2.
         -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
                 explicit time interval.  The start time may be specified as a
                 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.


         ssh-keygen may be used to generate groups for the Diffie-Hellman Group
         Exchange (DH-GEX) protocol.  Generating these groups is a two-step pro-
         cess: 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 tested 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/ssh/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
         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/  In
         both 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 -Z user1,user2
               $ ssh-keygen -s ca_key -I key_id -h -Z 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 have a maximum validity inter-
         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.


                 Contains the protocol version 1 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
                 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 protocol version 1 RSA public key for authentica-
                 tion.  The contents of this file should be added to
                 ~/.ssh/authorized_keys on all machines where the user wishes to
                 log in using RSA authentication.  There is no need to keep the
                 contents of this file secret.
                 ~/.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).


                 The reseeding of the OpenSSL random generator is usually done
                 from /dev/urandom.  If the SSH_USE_STRONG_RNG environment vari-
                 able is set to value other than 0 the OpenSSL random generator is
                 reseeded from /dev/random.  The number of bytes read is defined
                 by the SSH_USE_STRONG_RNG value.  Minimum is 14 bytes.  This set-
                 ting is not recommended on the computers without the hardware
                 random generator because insufficient entropy causes the connec-
                 tion to be blocked until enough entropy is available.


         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 December 10, 2018 BSD


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