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+SSH-KEYGEN(1) General Commands Manual SSH-KEYGEN(1)
+
+NAME
+ ssh-keygen M-bM-^@M-^S authentication key generation, management and conversion
+
+SYNOPSIS
+ 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 ...
+
+DESCRIPTION
+ 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
+ invoked 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+ Lists, and to test whether given keys have been revoked by one.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
+ /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 M-bM-^@M-^\.pubM-bM-^@M-^] 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
+ characters 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
+ 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 M-bM-^@M-^\user@hostM-bM-^@M-^] 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
+ resulting host key files. This is used by /etc/rc to generate
+ new host keys.
+
+ -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
+ file.
+
+ -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.
+ Generally, 2048 bits is considered sufficient. DSA keys must be
+ exactly 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
+ ignored.
+
+ -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
+ private keys, for the passphrase if the key has one, and for the
+ new comment.
+
+ -D pkcs11
+ Download the RSA public keys provided by the PKCS#11 shared
+ library pkcs11. When used in combination with -s, this option
+ indicates 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
+ fingerprints. Valid options are: M-bM-^@M-^\md5M-bM-^@M-^] and M-bM-^@M-^\sha256M-bM-^@M-^]. The
+ default is M-bM-^@M-^\sha256M-bM-^@M-^].
+
+ -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 M-bM-^@M-^\RFC4716M-bM-^@M-^]. This option
+ allows 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
+ 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-
+ 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 M-bM-^@M-^\RFC4716M-bM-^@M-^].
+
+ -J num_lines
+ Exit after screening the specified number of lines while
+ performing 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
+ performing DH candidate screening using the -T option. This will
+ be used to skip lines in the input file that have already been
+ processed 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
+ section.
+
+ -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
+ generating candidate moduli for DH-GEX.
+
+ -m key_format
+ Specify a key format for the -i (import) or -e (export)
+ conversion options. The supported key formats are: M-bM-^@M-^\RFC4716M-bM-^@M-^]
+ (RFC 4716/SSH2 public or private key), M-bM-^@M-^\PKCS8M-bM-^@M-^] (PEM PKCS8 public
+ key) or M-bM-^@M-^\PEMM-bM-^@M-^] (PEM public key). The default conversion format is
+ M-bM-^@M-^\RFC4716M-bM-^@M-^]. Setting a format of M-bM-^@M-^\PEMM-bM-^@M-^] 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
+ included 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
+ options that are valid for user certificates are:
+
+ clear Clear all enabled permissions. This is useful for
+ clearing the default set of permissions so permissions
+ may be added individually.
+
+ critical:name[=contents]
+ extension:name[=contents]
+ Includes an arbitrary certificate critical option or
+ extension. The specified name should include a domain
+ suffix, e.g. M-bM-^@M-^\name@example.comM-bM-^@M-^]. If contents is
+ specified then it is included as the contents of the
+ extension/option 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.
+
+ force-command=command
+ Forces the execution of command instead of any shell or
+ command specified by the user when the certificate is
+ used for authentication.
+
+ no-agent-forwarding
+ Disable ssh-agent(1) forwarding (permitted by default).
+
+ no-port-forwarding
+ Disable port forwarding (permitted by default).
+
+ no-pty Disable PTY allocation (permitted by default).
+
+ no-user-rc
+ Disable execution of ~/.ssh/rc by sshd(8) (permitted by
+ default).
+
+ no-x11-forwarding
+ Disable X11 forwarding (permitted by default).
+
+ permit-agent-forwarding
+ Allows ssh-agent(1) forwarding.
+
+ permit-port-forwarding
+ Allows port forwarding.
+
+ permit-pty
+ Allows PTY allocation.
+
+ permit-user-rc
+ Allows execution of ~/.ssh/rc by sshd(8).
+
+ permit-X11-forwarding
+ Allows X11 forwarding.
+
+ source-address=address_list
+ Restrict the source addresses from which the certificate
+ is considered valid. The address_list is a comma-
+ separated list of one or more address/netmask pairs in
+ CIDR format.
+
+ -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
+ above).
+
+ -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
+ DH-GEX.
+
+ -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
+ M-bM-^@M-^\dsaM-bM-^@M-^], M-bM-^@M-^\ecdsaM-bM-^@M-^], M-bM-^@M-^\ed25519M-bM-^@M-^], or M-bM-^@M-^\rsaM-bM-^@M-^].
+
+ -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
+ command line are added to the existing KRL rather than a new KRL
+ being created.
+
+ -V validity_interval
+ Specify a validity interval when signing a certificate. A
+ validity 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 the string M-bM-^@M-^\alwaysM-bM-^@M-^] to
+ indicate 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
+ YYYYMMDDHHMM[SS] time, a relative time starting with a plus
+ character or the string M-bM-^@M-^\foreverM-bM-^@M-^] to indicate that the
+ certificate has no expirty date.
+
+ For example: M-bM-^@M-^\+52w1dM-bM-^@M-^] (valid from now to 52 weeks and one day
+ from now), M-bM-^@M-^\-4w:+4wM-bM-^@M-^] (valid from four weeks ago to four weeks
+ from now), M-bM-^@M-^\20100101123000:20110101123000M-bM-^@M-^] (valid from 12:30 PM,
+ January 1st, 2010 to 12:30 PM, January 1st, 2011), M-bM-^@M-^\-1d:20110101M-bM-^@M-^]
+ (valid from yesterday to midnight, January 1st, 2011).
+ M-bM-^@M-^\-1m:foreverM-bM-^@M-^] (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
+ generation. Multiple -v options increase the verbosity. The
+ maximum is 3.
+
+ -W generator
+ Specify desired generator when testing candidate moduli for DH-
+ GEX.
+
+ -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
+ version number.
+
+MODULI GENERATION
+ 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
+ suitability (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
+ specifies 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.
+
+CERTIFICATES
+ 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
+ certificates authenticate users to servers, whereas host certificates
+ authenticate server hosts to users. To generate a user certificate:
+
+ $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub
+
+ The resultant certificate will be placed in /path/to/user_key-cert.pub.
+ A host certificate requires the -h option:
+
+ $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub
+
+ The host certificate will be output to /path/to/host_key-cert.pub.
+
+ It is possible to sign using a CA key stored in a PKCS#11 token by
+ providing the token library using -D and identifying the CA key by
+ providing its public half as an argument to -s:
+
+ $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub
+
+ 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
+ identified by its public half.
+
+ $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub
+
+ 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
+ principals:
+
+ $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub
+ $ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub
+
+ Additional limitations on the validity and use of user certificates may
+ be specified through certificate options. A certificate option may
+ disable 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
+ certificate that is presented at a time outside this range will not be
+ considered 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
+ public key must be trusted by sshd(8) or ssh(1). Please refer to those
+ manual pages for details.
+
+KEY REVOCATION LISTS
+ 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
+ either contain a KRL specification (see below) or public keys, listed one
+ per line. Plain public keys are revoked by listing their hash or
+ contents 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
+ original certificate on hand. A KRL specification consists of lines
+ containing one of the following directives followed by a colon and some
+ directive-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
+ expressed 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
+ option 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.
+
+FILES
+ ~/.ssh/id_dsa
+ ~/.ssh/id_ecdsa
+ ~/.ssh/id_ed25519
+ ~/.ssh/id_rsa
+ 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
+ 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.
+
+ ~/.ssh/id_dsa.pub
+ ~/.ssh/id_ecdsa.pub
+ ~/.ssh/id_ed25519.pub
+ ~/.ssh/id_rsa.pub
+ Contains the DSA, ECDSA, Ed25519 or RSA public key for
+ authentication. 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.
+
+ /etc/moduli
+ Contains Diffie-Hellman groups used for DH-GEX. The file format
+ is described in moduli(5).
+
+SEE ALSO
+ ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8)
+
+ The Secure Shell (SSH) Public Key File Format, RFC 4716, 2006.
+
+AUTHORS
+ 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
+ created OpenSSH. Markus Friedl contributed the support for SSH protocol
+ versions 1.5 and 2.0.
+
+OpenBSD 6.4 September 12, 2018 OpenBSD 6.4