{ "mode": "man", "parameter": "ssh-keygen", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ssh-keygen/1/json", "generated": "2026-07-05T15:12:36Z", "synopsis": "ssh-keygen [-q] [-a rounds] [-b bits] [-C comment] [-f outputkeyfile] [-m format]\n[-N newpassphrase] [-O option]\n[-t dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa] [-w provider] [-Z cipher]\nssh-keygen -p [-a rounds] [-f keyfile] [-m format] [-N newpassphrase] [-P oldpassphrase]\n[-Z cipher]\nssh-keygen -i [-f inputkeyfile] [-m keyformat]\nssh-keygen -e [-f inputkeyfile] [-m keyformat]\nssh-keygen -y [-f inputkeyfile]\nssh-keygen -c [-a rounds] [-C comment] [-f keyfile] [-P passphrase]\nssh-keygen -l [-v] [-E fingerprinthash] [-f inputkeyfile]\nssh-keygen -B [-f inputkeyfile]\nssh-keygen -D pkcs11\nssh-keygen -F hostname [-lv] [-f knownhostsfile]\nssh-keygen -H [-f knownhostsfile]\nssh-keygen -K [-a rounds] [-w provider]\nssh-keygen -R hostname [-f knownhostsfile]\nssh-keygen -r hostname [-g] [-f inputkeyfile]\nssh-keygen -M generate [-O option] outputfile\nssh-keygen -M screen [-f inputfile] [-O option] outputfile\nssh-keygen -I certificateidentity -s cakey [-hU] [-D pkcs11provider] [-n principals]\n[-O option] [-V validityinterval] [-z serialnumber] file ...\nssh-keygen -L [-f inputkeyfile]\nssh-keygen -A [-a rounds] [-f prefixpath]\nssh-keygen -k -f krlfile [-u] [-s capublic] [-z versionnumber] file ...\nssh-keygen -Q [-l] -f krlfile file ...\nssh-keygen -Y find-principals [-O option] -s signaturefile -f allowedsignersfile\nssh-keygen -Y match-principals -I signeridentity -f allowedsignersfile\nssh-keygen -Y check-novalidate [-O option] -n namespace -s signaturefile\nssh-keygen -Y sign [-O option] -f keyfile -n namespace file ...\nssh-keygen -Y verify [-O option] -f allowedsignersfile -I signeridentity -n namespace -s\nsignaturefile [-r revocationfile]", "sections": { "NAME": { "content": "ssh-keygen — OpenSSH authentication key utility\n", "subsections": [] }, "SYNOPSIS": { "content": "ssh-keygen [-q] [-a rounds] [-b bits] [-C comment] [-f outputkeyfile] [-m format]\n[-N newpassphrase] [-O option]\n[-t dsa | ecdsa | ecdsa-sk | ed25519 | ed25519-sk | rsa] [-w provider] [-Z cipher]\nssh-keygen -p [-a rounds] [-f keyfile] [-m format] [-N newpassphrase] [-P oldpassphrase]\n[-Z cipher]\nssh-keygen -i [-f inputkeyfile] [-m keyformat]\nssh-keygen -e [-f inputkeyfile] [-m keyformat]\nssh-keygen -y [-f inputkeyfile]\nssh-keygen -c [-a rounds] [-C comment] [-f keyfile] [-P passphrase]\nssh-keygen -l [-v] [-E fingerprinthash] [-f inputkeyfile]\nssh-keygen -B [-f inputkeyfile]\nssh-keygen -D pkcs11\nssh-keygen -F hostname [-lv] [-f knownhostsfile]\nssh-keygen -H [-f knownhostsfile]\nssh-keygen -K [-a rounds] [-w provider]\nssh-keygen -R hostname [-f knownhostsfile]\nssh-keygen -r hostname [-g] [-f inputkeyfile]\nssh-keygen -M generate [-O option] outputfile\nssh-keygen -M screen [-f inputfile] [-O option] outputfile\nssh-keygen -I certificateidentity -s cakey [-hU] [-D pkcs11provider] [-n principals]\n[-O option] [-V validityinterval] [-z serialnumber] file ...\nssh-keygen -L [-f inputkeyfile]\nssh-keygen -A [-a rounds] [-f prefixpath]\nssh-keygen -k -f krlfile [-u] [-s capublic] [-z versionnumber] file ...\nssh-keygen -Q [-l] -f krlfile file ...\nssh-keygen -Y find-principals [-O option] -s signaturefile -f allowedsignersfile\nssh-keygen -Y match-principals -I signeridentity -f allowedsignersfile\nssh-keygen -Y check-novalidate [-O option] -n namespace -s signaturefile\nssh-keygen -Y sign [-O option] -f keyfile -n namespace file ...\nssh-keygen -Y verify [-O option] -f allowedsignersfile -I signeridentity -n namespace -s\nsignaturefile [-r revocationfile]\n", "subsections": [] }, "DESCRIPTION": { "content": "ssh-keygen generates, manages and converts authentication keys for ssh(1). ssh-keygen can cre‐\nate keys for use by SSH protocol version 2.\n\nThe type of key to be generated is specified with the -t option. If invoked without any argu‐\nments, ssh-keygen will generate an RSA key.\n\nssh-keygen is also used to generate groups for use in Diffie-Hellman group exchange (DH-GEX).\nSee the MODULI GENERATION section for details.\n\nFinally, ssh-keygen can be used to generate and update Key Revocation Lists, and to test\nwhether given keys have been revoked by one. See the KEY REVOCATION LISTS section for details.\n\nNormally each user wishing to use SSH with public key authentication runs this once to create\nthe authentication key in ~/.ssh/iddsa, ~/.ssh/idecdsa, ~/.ssh/idecdsask,\n~/.ssh/ided25519, ~/.ssh/ided25519sk or ~/.ssh/idrsa. Additionally, the system administra‐\ntor may use this to generate host keys.\n\nNormally this program generates the key and asks for a file in which to store the private key.\nThe public key is stored in a file with the same name but “.pub” appended. The program also\nasks for a passphrase. The passphrase may be empty to indicate no passphrase (host keys must\nhave an empty passphrase), or it may be a string of arbitrary length. A passphrase is similar\nto a password, except it can be a phrase with a series of words, punctuation, numbers, white‐\nspace, or any string of characters you want. Good passphrases are 10-30 characters long, are\nnot simple sentences or otherwise easily guessable (English prose has only 1-2 bits of entropy\nper character, and provides very bad passphrases), and contain a mix of upper and lowercase\nletters, numbers, and non-alphanumeric characters. The passphrase can be changed later by us‐\ning the -p option.\n\nThere is no way to recover a lost passphrase. If the passphrase is lost or forgotten, a new\nkey must be generated and the corresponding public key copied to other machines.\n\nssh-keygen will by default write keys in an OpenSSH-specific format. This format is preferred\nas it offers better protection for keys at rest as well as allowing storage of key comments\nwithin the private key file itself. The key comment may be useful to help identify the key.\nThe comment is initialized to “user@host” when the key is created, but can be changed using the", "subsections": [ { "name": "-c", "content": "It is still possible for ssh-keygen to write the previously-used PEM format private keys using\nthe -m flag. This may be used when generating new keys, and existing new-format keys may be\nconverted using this option in conjunction with the -p (change passphrase) flag.\n\nAfter a key is generated, ssh-keygen will ask where the keys should be placed to be activated.\n\nThe options are as follows:\n", "flag": "-c" }, { "name": "-A", "content": "ist, generate the host keys with the default key file path, an empty passphrase, de‐\nfault bits for the key type, and default comment. If -f has also been specified, its\nargument is used as a prefix to the default path for the resulting host key files.\nThis is used by system administration scripts to generate new host keys.\n", "flag": "-A" }, { "name": "-a", "content": "When saving a private key, this option specifies the number of KDF (key derivation\nfunction, currently bcryptpbkdf(3)) rounds used. Higher numbers result in slower\npassphrase verification and increased resistance to brute-force password cracking\n(should the keys be stolen). The default is 16 rounds.\n", "flag": "-a" }, { "name": "-B", "content": "", "flag": "-B" }, { "name": "-b", "content": "Specifies the number of bits in the key to create. For RSA keys, the minimum size is\n1024 bits and the default is 3072 bits. Generally, 3072 bits is considered sufficient.\nDSA keys must be exactly 1024 bits as specified by FIPS 186-2. For ECDSA keys, the -b\nflag determines the key length by selecting from one of three elliptic curve sizes:\n256, 384 or 521 bits. Attempting to use bit lengths other than these three values for\nECDSA keys will fail. ECDSA-SK, Ed25519 and Ed25519-SK keys have a fixed length and\nthe -b flag will be ignored.\n", "flag": "-b" }, { "name": "-C", "content": "Provides a new comment.\n", "flag": "-C" }, { "name": "-c", "content": "prompt for the file containing the private keys, for the passphrase if the key has one,\nand for the new comment.\n", "flag": "-c" }, { "name": "-D", "content": "Download the public keys provided by the PKCS#11 shared library pkcs11. When used in\ncombination with -s, this option indicates that a CA key resides in a PKCS#11 token\n(see the CERTIFICATES section for details).\n", "flag": "-D" }, { "name": "-E", "content": "Specifies the hash algorithm used when displaying key fingerprints. Valid options are:\n“md5” and “sha256”. The default is “sha256”.\n", "flag": "-E" }, { "name": "-e", "content": "key in one of the formats specified by the -m option. The default export format is\n“RFC4716”. This option allows exporting OpenSSH keys for use by other programs, in‐\ncluding several commercial SSH implementations.\n", "flag": "-e" }, { "name": "-F", "content": "Search for the specified hostname (with optional port number) in a knownhosts file,\nlisting any occurrences found. This option is useful to find hashed host names or ad‐\ndresses and may also be used in conjunction with the -H option to print found keys in a\nhashed format.\n", "flag": "-F" }, { "name": "-f", "content": "Specifies the filename of the key file.\n", "flag": "-f" }, { "name": "-g -r", "content": "", "flag": "-r" }, { "name": "-H", "content": "sentations within the specified file; the original content is moved to a file with a\n.old suffix. These hashes may be used normally by ssh and sshd, but they do not reveal\nidentifying information should the file's contents be disclosed. This option will not\nmodify existing hashed hostnames and is therefore safe to use on files that mix hashed\nand non-hashed names.\n", "flag": "-H" }, { "name": "-h", "content": "CERTIFICATES section for details.\n", "flag": "-h" }, { "name": "-I", "content": "Specify the key identity when signing a public key. See the CERTIFICATES section for\ndetails.\n", "flag": "-I" }, { "name": "-i", "content": "fied by the -m option and print an OpenSSH compatible private (or public) key to std‐\nout. This option allows importing keys from other software, including several commer‐\ncial SSH implementations. The default import format is “RFC4716”.\n", "flag": "-i" }, { "name": "-K", "content": "written to the current directory for each downloaded key. If multiple FIDO authentica‐\ntors are attached, keys will be downloaded from the first touched authenticator.\n", "flag": "-K" }, { "name": "-k", "content": "specified via the -f flag that revokes every key or certificate presented on the com‐\nmand line. Keys/certificates to be revoked may be specified by public key file or us‐\ning the format described in the KEY REVOCATION LISTS section.\n", "flag": "-k" }, { "name": "-L", "content": "", "flag": "-L" }, { "name": "-l", "content": "to find the matching public key file and prints its fingerprint. If combined with -v,\na visual ASCII art representation of the key is supplied with the fingerprint.\n", "flag": "-l" }, { "name": "-M generate", "content": "Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for eventual use\nby the ‘diffie-hellman-group-exchange-*’ key exchange methods. The numbers generated\nby this operation must be further screened before use. See the MODULI GENERATION sec‐\ntion for more information.\n", "flag": "-M" }, { "name": "-M screen", "content": "Screen candidate parameters for Diffie-Hellman Group Exchange. This will accept a list\nof candidate numbers and test that they are safe (Sophie Germain) primes with accept‐\nable group generators. The results of this operation may be added to the\n/etc/ssh/moduli file. See the MODULI GENERATION section for more information.\n", "flag": "-M" }, { "name": "-m", "content": "Specify a key format for key generation, the -i (import), -e (export) conversion op‐\ntions, and the -p change passphrase operation. The latter may be used to convert be‐\ntween OpenSSH private key and PEM private key formats. The supported key formats are:\n“RFC4716” (RFC 4716/SSH2 public or private key), “PKCS8” (PKCS8 public or private key)\nor “PEM” (PEM public key). By default OpenSSH will write newly-generated private keys\nin its own format, but when converting public keys for export the default format is\n“RFC4716”. Setting a format of “PEM” when generating or updating a supported private\nkey type will cause the key to be stored in the legacy PEM private key format.\n", "flag": "-m" }, { "name": "-N", "content": "Provides the new passphrase.\n", "flag": "-N" }, { "name": "-n", "content": "Specify one or more principals (user or host names) to be included in a certificate\nwhen signing a key. Multiple principals may be specified, separated by commas. See\nthe CERTIFICATES section for details.\n", "flag": "-n" }, { "name": "-O", "content": "Specify a key/value option. These are specific to the operation that ssh-keygen has\nbeen requested to perform.\n\nWhen signing certificates, one of the options listed in the CERTIFICATES section may be\nspecified here.\n\nWhen performing moduli generation or screening, one of the options listed in the MODULI\nGENERATION section may be specified.\n\nWhen generating a key that will be hosted on a FIDO authenticator, this flag may be\nused to specify key-specific options. Those supported at present are:\n\napplication\nOverride the default FIDO application/origin string of “ssh:”. This may be\nuseful when generating host or domain-specific resident keys. The specified\napplication string must begin with “ssh:”.\n\nchallenge=path\nSpecifies a path to a challenge string that will be passed to the FIDO token\nduring key generation. The challenge string may be used as part of an out-of-\nband protocol for key enrollment (a random challenge is used by default).\n\ndevice Explicitly specify a fido(4) device to use, rather than letting the token mid‐\ndleware select one.\n\nno-touch-required\nIndicate that the generated private key should not require touch events (user\npresence) when making signatures. Note that sshd(8) will refuse such signa‐\ntures by default, unless overridden via an authorizedkeys option.\n\nresident\nIndicate that the key should be stored on the FIDO authenticator itself. Resi‐\ndent keys may be supported on FIDO2 tokens and typically require that a PIN be\nset on the token prior to generation. Resident keys may be loaded off the to‐\nken using ssh-add(1).\n\nuser A username to be associated with a resident key, overriding the empty default\nusername. Specifying a username may be useful when generating multiple resi‐\ndent keys for the same application name.\n\nverify-required\nIndicate that this private key should require user verification for each signa‐\nture. Not all FIDO tokens support this option. Currently PIN authentication\nis the only supported verification method, but other methods may be supported\nin the future.\n\nwrite-attestation=path\nMay be used at key generation time to record the attestation data returned from\nFIDO tokens during key generation. This information is potentially sensitive.\nBy default, this information is discarded.\n\nWhen performing signature-related options using the -Y flag, the following options are\naccepted:\n\nhashalg=algorithm\nSelects the hash algorithm to use for hashing the message to be signed. Valid\nalgorithms are “sha256” and “sha512.” The default is “sha512.”\n\nprint-pubkey\nPrint the full public key to standard output after signature verification.\n\nverify-time=timestamp\nSpecifies a time to use when validating signatures instead of the current time.\nThe time may be specified as a date in YYYYMMDD format or a time in YYYYMMD‐\nDHHMM[SS] format.\n\nThe -O option may be specified multiple times.\n", "flag": "-O" }, { "name": "-P", "content": "Provides the (old) passphrase.\n", "flag": "-P" }, { "name": "-p", "content": "vate key. The program will prompt for the file containing the private key, for the old\npassphrase, and twice for the new passphrase.\n", "flag": "-p" }, { "name": "-Q -l", "content": "the contents of the KRL will be printed.\n", "flag": "-l" }, { "name": "-q", "content": "", "flag": "-q" }, { "name": "-R", "content": "Removes all keys belonging to the specified hostname (with optional port number) from a\nknownhosts file. This option is useful to delete hashed hosts (see the -H option\nabove).\n", "flag": "-R" }, { "name": "-r", "content": "Print the SSHFP fingerprint resource record named hostname for the specified public key\nfile.\n", "flag": "-r" }, { "name": "-s", "content": "Certify (sign) a public key using the specified CA key. See the CERTIFICATES section\nfor details.\n\nWhen generating a KRL, -s specifies a path to a CA public key file used to revoke cer‐\ntificates directly by key ID or serial number. See the KEY REVOCATION LISTS section\nfor details.\n", "flag": "-s" }, { "name": "-t", "content": "Specifies the type of key to create. The possible values are “dsa”, “ecdsa”,\n“ecdsa-sk”, “ed25519”, “ed25519-sk”, or “rsa”.\n\nThis flag may also be used to specify the desired signature type when signing certifi‐\ncates using an RSA CA key. The available RSA signature variants are “ssh-rsa” (SHA1\nsignatures, not recommended), “rsa-sha2-256”, and “rsa-sha2-512” (the default).\n", "flag": "-t" }, { "name": "-U -s", "content": "ssh-agent(1). See the CERTIFICATES section for more information.\n", "flag": "-s" }, { "name": "-u -k", "content": "the existing KRL rather than a new KRL being created.\n", "flag": "-k" }, { "name": "-V", "content": "Specify a validity interval when signing a certificate. A validity interval may con‐\nsist of a single time, indicating that the certificate is valid beginning now and ex‐\npiring at that time, or may consist of two times separated by a colon to indicate an\nexplicit time interval.\n\nThe start time may be specified as the string “always” to indicate the certificate has\nno specified start time, a date in YYYYMMDD format, a time in YYYYMMDDHHMM[SS] format,\na relative time (to the current time) consisting of a minus sign followed by an inter‐\nval in the format described in the TIME FORMATS section of sshdconfig(5).\n\nThe end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMM[SS] time, a relative\ntime starting with a plus character or the string “forever” to indicate that the cer‐\ntificate has no expiry date.\n\nFor example: “+52w1d” (valid from now to 52 weeks and one day from now), “-4w:+4w”\n(valid from four weeks ago to four weeks from now), “20100101123000:20110101123000”\n(valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), “-1d:20110101”\n(valid from yesterday to midnight, January 1st, 2011), “-1m:forever” (valid from one\nminute ago and never expiring).\n", "flag": "-V" }, { "name": "-v", "content": "is helpful for debugging moduli generation. Multiple -v options increase the ver‐\nbosity. The maximum is 3.\n", "flag": "-v" }, { "name": "-w", "content": "Specifies a path to a library that will be used when creating FIDO authenticator-hosted\nkeys, overriding the default of using the internal USB HID support.\n", "flag": "-w" }, { "name": "-Y find-principals", "content": "Find the principal(s) associated with the public key of a signature, provided using the\n-s flag in an authorized signers file provided using the -f flag. The format of the\nallowed signers file is documented in the ALLOWED SIGNERS section below. If one or\nmore matching principals are found, they are returned on standard output.\n", "flag": "-Y" }, { "name": "-Y match-principals", "content": "Find principal matching the principal name provided using the -I flag in the authorized\nsigners file specified using the -f flag. If one or more matching principals are\nfound, they are returned on standard output.\n", "flag": "-Y" }, { "name": "-Y check-novalidate", "content": "Checks that a signature generated using ssh-keygen -Y sign has a valid structure. This\ndoes not validate if a signature comes from an authorized signer. When testing a sig‐\nnature, ssh-keygen accepts a message on standard input and a signature namespace using\n-n. A file containing the corresponding signature must also be supplied using the -s\nflag. Successful testing of the signature is signalled by ssh-keygen returning a zero\nexit status.\n", "flag": "-Y" }, { "name": "-Y sign", "content": "Cryptographically sign a file or some data using a SSH key. When signing, ssh-keygen\naccepts zero or more files to sign on the command-line - if no files are specified then\nssh-keygen will sign data presented on standard input. Signatures are written to the\npath of the input file with “.sig” appended, or to standard output if the message to be\nsigned was read from standard input.\n\nThe key used for signing is specified using the -f option and may refer to either a\nprivate key, or a public key with the private half available via ssh-agent(1). An ad‐\nditional signature namespace, used to prevent signature confusion across different do‐\nmains of use (e.g. file signing vs email signing) must be provided via the -n flag.\nNamespaces are arbitrary strings, and may include: “file” for file signing, “email” for\nemail signing. For custom uses, it is recommended to use names following a NAME‐\nSPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces.\n", "flag": "-Y" }, { "name": "-Y verify", "content": "Request to verify a signature generated using ssh-keygen -Y sign as described above.\nWhen verifying a signature, ssh-keygen accepts a message on standard input and a signa‐\nture namespace using -n. A file containing the corresponding signature must also be\nsupplied using the -s flag, along with the identity of the signer using -I and a list\nof allowed signers via the -f flag. The format of the allowed signers file is docu‐\nmented in the ALLOWED SIGNERS section below. A file containing revoked keys can be\npassed using the -r flag. The revocation file may be a KRL or a one-per-line list of\npublic keys. Successful verification by an authorized signer is signalled by\nssh-keygen returning a zero exit status.\n", "flag": "-Y" }, { "name": "-y", "content": "stdout.\n", "flag": "-y" }, { "name": "-Z", "content": "Specifies the cipher to use for encryption when writing an OpenSSH-format private key\nfile. The list of available ciphers may be obtained using \"ssh -Q cipher\". The de‐\nfault is “aes256-ctr”.\n", "flag": "-Z" }, { "name": "-z", "content": "Specifies a serial number to be embedded in the certificate to distinguish this cer‐\ntificate from others from the same CA. If the serialnumber is prefixed with a ‘+’\ncharacter, then the serial number will be incremented for each certificate signed on a\nsingle command-line. The default serial number is zero.\n\nWhen generating a KRL, the -z flag is used to specify a KRL version number.\n", "flag": "-z" } ] }, "MODULI GENERATION": { "content": "ssh-keygen may be used to generate groups for the Diffie-Hellman Group Exchange (DH-GEX) proto‐\ncol. Generating these groups is a two-step process: first, candidate primes are generated us‐\ning a fast, but memory intensive process. These candidate primes are then tested for suitabil‐\nity (a CPU-intensive process).\n\nGeneration of primes is performed using the -M generate option. The desired length of the\nprimes may be specified by the -O bits option. For example:\n\n# ssh-keygen -M generate -O bits=2048 moduli-2048.candidates\n\nBy default, the search for primes begins at a random point in the desired length range. This\nmay be overridden using the -O start option, which specifies a different start point (in hex).\n\nOnce a set of candidates have been generated, they must be screened for suitability. This may\nbe performed using the -M screen option. In this mode ssh-keygen will read candidates from\nstandard input (or a file specified using the -f option). For example:\n\n# ssh-keygen -M screen -f moduli-2048.candidates moduli-2048\n\nBy default, each candidate will be subjected to 100 primality tests. This may be overridden\nusing the -O prime-tests option. The DH generator value will be chosen automatically for the\nprime under consideration. If a specific generator is desired, it may be requested using the", "subsections": [ { "name": "-O", "content": "Screened DH groups may be installed in /etc/ssh/moduli. It is important that this file con‐\ntains moduli of a range of bit lengths.\n\nA number of options are available for moduli generation and screening via the -O flag:\n\nlines=number\nExit after screening the specified number of lines while performing DH candidate\nscreening.\n\nstart-line=line-number\nStart screening at the specified line number while performing DH candidate screening.\n\ncheckpoint=filename\nWrite the last line processed to the specified file while performing DH candidate\nscreening. This will be used to skip lines in the input file that have already been\nprocessed if the job is restarted.\n\nmemory=mbytes\nSpecify the amount of memory to use (in megabytes) when generating candidate moduli for\nDH-GEX.\n\nstart=hex-value\nSpecify start point (in hex) when generating candidate moduli for DH-GEX.\n\ngenerator=value\nSpecify desired generator (in decimal) when testing candidate moduli for DH-GEX.\n", "flag": "-O" } ] }, "CERTIFICATES": { "content": "ssh-keygen supports signing of keys to produce certificates that may be used for user or host\nauthentication. Certificates consist of a public key, some identity information, zero or more\nprincipal (user or host) names and a set of options that are signed by a Certification Author‐\nity (CA) key. Clients or servers may then trust only the CA key and verify its signature on a\ncertificate rather than trusting many user/host keys. Note that OpenSSH certificates are a\ndifferent, and much simpler, format to the X.509 certificates used in ssl(8).\n\nssh-keygen supports two types of certificates: user and host. User certificates authenticate\nusers to servers, whereas host certificates authenticate server hosts to users. To generate a\nuser certificate:\n\n$ ssh-keygen -s /path/to/cakey -I keyid /path/to/userkey.pub\n\nThe resultant certificate will be placed in /path/to/userkey-cert.pub. A host certificate re‐\nquires the -h option:\n\n$ ssh-keygen -s /path/to/cakey -I keyid -h /path/to/hostkey.pub\n\nThe host certificate will be output to /path/to/hostkey-cert.pub.\n\nIt is possible to sign using a CA key stored in a PKCS#11 token by providing the token library\nusing -D and identifying the CA key by providing its public half as an argument to -s:\n\n$ ssh-keygen -s cakey.pub -D libpkcs11.so -I keyid userkey.pub\n\nSimilarly, it is possible for the CA key to be hosted in a ssh-agent(1). This is indicated by\nthe -U flag and, again, the CA key must be identified by its public half.\n\n$ ssh-keygen -Us cakey.pub -I keyid userkey.pub\n\nIn all cases, keyid is a \"key identifier\" that is logged by the server when the certificate is\nused for authentication.\n\nCertificates may be limited to be valid for a set of principal (user/host) names. By default,\ngenerated certificates are valid for all users or hosts. To generate a certificate for a spec‐\nified set of principals:\n\n$ ssh-keygen -s cakey -I keyid -n user1,user2 userkey.pub\n$ ssh-keygen -s cakey -I keyid -h -n host.domain hostkey.pub\n\nAdditional limitations on the validity and use of user certificates may be specified through\ncertificate options. A certificate option may disable features of the SSH session, may be\nvalid only when presented from particular source addresses or may force the use of a specific\ncommand.\n\nThe options that are valid for user certificates are:\n\nclear Clear all enabled permissions. This is useful for clearing the default set of permis‐\nsions so permissions may be added individually.\n\ncritical:name[=contents]\nextension:name[=contents]\nIncludes an arbitrary certificate critical option or extension. The specified name\nshould include a domain suffix, e.g. “name@example.com”. If contents is specified then\nit is included as the contents of the extension/option encoded as a string, otherwise\nthe extension/option is created with no contents (usually indicating a flag). Exten‐\nsions may be ignored by a client or server that does not recognise them, whereas un‐\nknown critical options will cause the certificate to be refused.\n\nforce-command=command\nForces the execution of command instead of any shell or command specified by the user\nwhen the certificate is used for authentication.\n", "subsections": [ { "name": "no-agent-forwarding", "content": "Disable ssh-agent(1) forwarding (permitted by default).\n" }, { "name": "no-port-forwarding", "content": "Disable port forwarding (permitted by default).\n\nno-pty Disable PTY allocation (permitted by default).\n" }, { "name": "no-user-rc", "content": "Disable execution of ~/.ssh/rc by sshd(8) (permitted by default).\n" }, { "name": "no-x11-forwarding", "content": "Disable X11 forwarding (permitted by default).\n" }, { "name": "permit-agent-forwarding", "content": "Allows ssh-agent(1) forwarding.\n" }, { "name": "permit-port-forwarding", "content": "Allows port forwarding.\n" }, { "name": "permit-pty", "content": "Allows PTY allocation.\n" }, { "name": "permit-user-rc", "content": "Allows execution of ~/.ssh/rc by sshd(8).\n" }, { "name": "permit-X11-forwarding", "content": "Allows X11 forwarding.\n" }, { "name": "no-touch-required", "content": "Do not require signatures made using this key include demonstration of user presence\n(e.g. by having the user touch the authenticator). This option only makes sense for\nthe FIDO authenticator algorithms ecdsa-sk and ed25519-sk.\n\nsource-address=addresslist\nRestrict the source addresses from which the certificate is considered valid. The\naddresslist is a comma-separated list of one or more address/netmask pairs in CIDR\nformat.\n" }, { "name": "verify-required", "content": "Require signatures made using this key indicate that the user was first verified. This\noption only makes sense for the FIDO authenticator algorithms ecdsa-sk and ed25519-sk.\nCurrently PIN authentication is the only supported verification method, but other meth‐\nods may be supported in the future.\n\nAt present, no standard options are valid for host keys.\n\nFinally, certificates may be defined with a validity lifetime. The -V option allows specifica‐\ntion of certificate start and end times. A certificate that is presented at a time outside\nthis range will not be considered valid. By default, certificates are valid from the UNIX\nEpoch to the distant future.\n\nFor certificates to be used for user or host authentication, the CA public key must be trusted\nby sshd(8) or ssh(1). Refer to those manual pages for details.\n" } ] }, "KEY REVOCATION LISTS": { "content": "ssh-keygen is able to manage OpenSSH format Key Revocation Lists (KRLs). These binary files\nspecify keys or certificates to be revoked using a compact format, taking as little as one bit\nper certificate if they are being revoked by serial number.\n\nKRLs may be generated using the -k flag. This option reads one or more files from the command\nline and generates a new KRL. The files may either contain a KRL specification (see below) or\npublic keys, listed one per line. Plain public keys are revoked by listing their hash or con‐\ntents in the KRL and certificates revoked by serial number or key ID (if the serial is zero or\nnot available).\n\nRevoking keys using a KRL specification offers explicit control over the types of record used\nto revoke keys and may be used to directly revoke certificates by serial number or key ID with‐\nout having the complete original certificate on hand. A KRL specification consists of lines\ncontaining one of the following directives followed by a colon and some directive-specific in‐\nformation.\n\nserial: serialnumber[-serialnumber]\nRevokes a certificate with the specified serial number. Serial numbers are 64-bit val‐\nues, not including zero and may be expressed in decimal, hex or octal. If two serial\nnumbers are specified separated by a hyphen, then the range of serial numbers including\nand between each is revoked. The CA key must have been specified on the ssh-keygen\ncommand line using the -s option.\n\nid: keyid\nRevokes a certificate with the specified key ID string. The CA key must have been\nspecified on the ssh-keygen command line using the -s option.\n\nkey: publickey\nRevokes the specified key. If a certificate is listed, then it is revoked as a plain\npublic key.\n\nsha1: publickey\nRevokes the specified key by including its SHA1 hash in the KRL.\n\nsha256: publickey\nRevokes the specified key by including its SHA256 hash in the KRL. KRLs that revoke\nkeys by SHA256 hash are not supported by OpenSSH versions prior to 7.9.\n\nhash: fingerprint\nRevokes a key using a fingerprint hash, as obtained from a sshd(8) authentication log\nmessage or the ssh-keygen -l flag. Only SHA256 fingerprints are supported here and re‐\nsultant KRLs are not supported by OpenSSH versions prior to 7.9.\n\nKRLs may be updated using the -u flag in addition to -k. When this option is specified, keys\nlisted via the command line are merged into the KRL, adding to those already there.\n\nIt is also possible, given a KRL, to test whether it revokes a particular key (or keys). The", "subsections": [ { "name": "-Q", "content": "listed on the command line has been revoked (or an error encountered) then ssh-keygen will exit\nwith a non-zero exit status. A zero exit status will only be returned if no key was revoked.\n", "flag": "-Q" } ] }, "ALLOWED SIGNERS": { "content": "When verifying signatures, ssh-keygen uses a simple list of identities and keys to determine\nwhether a signature comes from an authorized source. This \"allowed signers\" file uses a format\npatterned after the AUTHORIZEDKEYS FILE FORMAT described in sshd(8). Each line of the file\ncontains the following space-separated fields: principals, options, keytype, base64-encoded\nkey. Empty lines and lines starting with a ‘#’ are ignored as comments.\n\nThe principals field is a pattern-list (see PATTERNS in sshconfig(5)) consisting of one or\nmore comma-separated USER@DOMAIN identity patterns that are accepted for signing. When verify‐\ning, the identity presented via the -I option must match a principals pattern in order for the\ncorresponding key to be considered acceptable for verification.\n\nThe options (if present) consist of comma-separated option specifications. No spaces are per‐\nmitted, except within double quotes. The following option specifications are supported (note\nthat option keywords are case-insensitive):\n", "subsections": [ { "name": "cert-authority", "content": "Indicates that this key is accepted as a certificate authority (CA) and that certifi‐\ncates signed by this CA may be accepted for verification.\n\nnamespaces=namespace-list\nSpecifies a pattern-list of namespaces that are accepted for this key. If this option\nis present, the signature namespace embedded in the signature object and presented on\nthe verification command-line must match the specified list before the key will be con‐\nsidered acceptable.\n\nvalid-after=timestamp\nIndicates that the key is valid for use at or after the specified timestamp, which may\nbe a date in YYYYMMDD format or a time in YYYYMMDDHHMM[SS] format.\n\nvalid-before=timestamp\nIndicates that the key is valid for use at or before the specified timestamp.\n\nWhen verifying signatures made by certificates, the expected principal name must match both the\nprincipals pattern in the allowed signers file and the principals embedded in the certificate\nitself.\n\nAn example allowed signers file:\n\n# Comments allowed at start of line\nuser1@example.com,user2@example.com ssh-rsa AAAAX1...\n# A certificate authority, trusted for all principals in a domain.\n*@example.com cert-authority ssh-ed25519 AAAB4...\n# A key that is accepted only for file signing.\nuser2@example.com namespaces=\"file\" ssh-ed25519 AAA41...\n" } ] }, "ENVIRONMENT": { "content": "SSHSKPROVIDER\nSpecifies a path to a library that will be used when loading any FIDO authenticator-\nhosted keys, overriding the default of using the built-in USB HID support.\n", "subsections": [] }, "FILES": { "content": "~/.ssh/iddsa\n~/.ssh/idecdsa\n~/.ssh/idecdsask\n~/.ssh/ided25519\n~/.ssh/ided25519sk\n~/.ssh/idrsa\nContains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, authenticator-hosted\nEd25519 or RSA authentication identity of the user. This file should not be readable\nby anyone but the user. It is possible to specify a passphrase when generating the\nkey; that passphrase will be used to encrypt the private part of this file using\n128-bit AES. This file is not automatically accessed by ssh-keygen but it is offered\nas the default file for the private key. ssh(1) will read this file when a login at‐\ntempt is made.\n\n~/.ssh/iddsa.pub\n~/.ssh/idecdsa.pub\n~/.ssh/idecdsask.pub\n~/.ssh/ided25519.pub\n~/.ssh/ided25519sk.pub\n~/.ssh/idrsa.pub\nContains the DSA, ECDSA, authenticator-hosted ECDSA, Ed25519, authenticator-hosted\nEd25519 or RSA public key for authentication. The contents of this file should be\nadded to ~/.ssh/authorizedkeys on all machines where the user wishes to log in using\npublic key authentication. There is no need to keep the contents of this file secret.\n\n/etc/ssh/moduli\nContains Diffie-Hellman groups used for DH-GEX. The file format is described in\nmoduli(5).\n", "subsections": [] }, "SEE ALSO": { "content": "ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8)\n\nThe Secure Shell (SSH) Public Key File Format, RFC 4716, 2006.\n", "subsections": [] }, "AUTHORS": { "content": "OpenSSH is a derivative of the original and free ssh 1.2.12 release by Tatu Ylonen. Aaron\nCampbell, Bob Beck, Markus Friedl, Niels Provos, Theo de Raadt and Dug Song removed many bugs,\nre-added newer features and created OpenSSH. Markus Friedl contributed the support for SSH\nprotocol versions 1.5 and 2.0.\n\nBSD February 6, 2022 BSD", "subsections": [] } }, "summary": "ssh-keygen — OpenSSH authentication key utility", "flags": [ { "flag": "-c", "long": null, "arg": null, "description": "It is still possible for ssh-keygen to write the previously-used PEM format private keys using the -m flag. This may be used when generating new keys, and existing new-format keys may be converted using this option in conjunction with the -p (change passphrase) flag. After a key is generated, ssh-keygen will ask where the keys should be placed to be activated. The options are as follows:" }, { "flag": "-A", "long": null, "arg": null, "description": "ist, generate the host keys with the default key file path, an empty passphrase, de‐ fault 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 system administration scripts to generate new host keys." }, { "flag": "-a", "long": null, "arg": null, "description": "When saving a private key, this option specifies the number of KDF (key derivation function, currently bcryptpbkdf(3)) rounds used. Higher numbers result in slower passphrase verification and increased resistance to brute-force password cracking (should the keys be stolen). The default is 16 rounds." }, { "flag": "-B", "long": null, "arg": null, "description": "" }, { "flag": "-b", "long": null, "arg": null, "description": "Specifies the number of bits in the key to create. For RSA keys, the minimum size is 1024 bits and the default is 3072 bits. Generally, 3072 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. ECDSA-SK, Ed25519 and Ed25519-SK keys have a fixed length and the -b flag will be ignored." }, { "flag": "-C", "long": null, "arg": null, "description": "Provides a new comment." }, { "flag": "-c", "long": null, "arg": null, "description": "prompt for the file containing the private keys, for the passphrase if the key has one, and for the new comment." }, { "flag": "-D", "long": null, "arg": null, "description": "Download the 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)." }, { "flag": "-E", "long": null, "arg": null, "description": "Specifies the hash algorithm used when displaying key fingerprints. Valid options are: “md5” and “sha256”. The default is “sha256”." }, { "flag": "-e", "long": null, "arg": null, "description": "key in one of the formats specified by the -m option. The default export format is “RFC4716”. This option allows exporting OpenSSH keys for use by other programs, in‐ cluding several commercial SSH implementations." }, { "flag": "-F", "long": null, "arg": null, "description": "Search for the specified hostname (with optional port number) in a knownhosts file, listing any occurrences found. This option is useful to find hashed host names or ad‐ dresses and may also be used in conjunction with the -H option to print found keys in a hashed format." }, { "flag": "-f", "long": null, "arg": null, "description": "Specifies the filename of the key file." }, { "flag": "-r", "long": null, "arg": null, "description": "" }, { "flag": "-H", "long": null, "arg": null, "description": "sentations 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." }, { "flag": "-h", "long": null, "arg": null, "description": "CERTIFICATES section for details." }, { "flag": "-I", "long": null, "arg": null, "description": "Specify the key identity when signing a public key. See the CERTIFICATES section for details." }, { "flag": "-i", "long": null, "arg": null, "description": "fied by the -m option and print an OpenSSH compatible private (or public) key to std‐ out. This option allows importing keys from other software, including several commer‐ cial SSH implementations. The default import format is “RFC4716”." }, { "flag": "-K", "long": null, "arg": null, "description": "written to the current directory for each downloaded key. If multiple FIDO authentica‐ tors are attached, keys will be downloaded from the first touched authenticator." }, { "flag": "-k", "long": null, "arg": null, "description": "specified via the -f flag that revokes every key or certificate presented on the com‐ mand line. Keys/certificates to be revoked may be specified by public key file or us‐ ing the format described in the KEY REVOCATION LISTS section." }, { "flag": "-L", "long": null, "arg": null, "description": "" }, { "flag": "-l", "long": null, "arg": null, "description": "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." }, { "flag": "-M", "long": null, "arg": null, "description": "Generate candidate Diffie-Hellman Group Exchange (DH-GEX) parameters for eventual use by the ‘diffie-hellman-group-exchange-*’ key exchange methods. The numbers generated by this operation must be further screened before use. See the MODULI GENERATION sec‐ tion for more information." }, { "flag": "-M", "long": null, "arg": null, "description": "Screen candidate parameters for Diffie-Hellman Group Exchange. This will accept a list of candidate numbers and test that they are safe (Sophie Germain) primes with accept‐ able group generators. The results of this operation may be added to the /etc/ssh/moduli file. See the MODULI GENERATION section for more information." }, { "flag": "-m", "long": null, "arg": null, "description": "Specify a key format for key generation, the -i (import), -e (export) conversion op‐ tions, and the -p change passphrase operation. The latter may be used to convert be‐ tween OpenSSH private key and PEM private key formats. The supported key formats are: “RFC4716” (RFC 4716/SSH2 public or private key), “PKCS8” (PKCS8 public or private key) or “PEM” (PEM public key). By default OpenSSH will write newly-generated private keys in its own format, but when converting public keys for export the default 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." }, { "flag": "-N", "long": null, "arg": null, "description": "Provides the new passphrase." }, { "flag": "-n", "long": null, "arg": null, "description": "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. See the CERTIFICATES section for details." }, { "flag": "-O", "long": null, "arg": null, "description": "Specify a key/value option. These are specific to the operation that ssh-keygen has been requested to perform. When signing certificates, one of the options listed in the CERTIFICATES section may be specified here. When performing moduli generation or screening, one of the options listed in the MODULI GENERATION section may be specified. When generating a key that will be hosted on a FIDO authenticator, this flag may be used to specify key-specific options. Those supported at present are: application Override the default FIDO application/origin string of “ssh:”. This may be useful when generating host or domain-specific resident keys. The specified application string must begin with “ssh:”. challenge=path Specifies a path to a challenge string that will be passed to the FIDO token during key generation. The challenge string may be used as part of an out-of- band protocol for key enrollment (a random challenge is used by default). device Explicitly specify a fido(4) device to use, rather than letting the token mid‐ dleware select one. no-touch-required Indicate that the generated private key should not require touch events (user presence) when making signatures. Note that sshd(8) will refuse such signa‐ tures by default, unless overridden via an authorizedkeys option. resident Indicate that the key should be stored on the FIDO authenticator itself. Resi‐ dent keys may be supported on FIDO2 tokens and typically require that a PIN be set on the token prior to generation. Resident keys may be loaded off the to‐ ken using ssh-add(1). user A username to be associated with a resident key, overriding the empty default username. Specifying a username may be useful when generating multiple resi‐ dent keys for the same application name. verify-required Indicate that this private key should require user verification for each signa‐ ture. Not all FIDO tokens support this option. Currently PIN authentication is the only supported verification method, but other methods may be supported in the future. write-attestation=path May be used at key generation time to record the attestation data returned from FIDO tokens during key generation. This information is potentially sensitive. By default, this information is discarded. When performing signature-related options using the -Y flag, the following options are accepted: hashalg=algorithm Selects the hash algorithm to use for hashing the message to be signed. Valid algorithms are “sha256” and “sha512.” The default is “sha512.” print-pubkey Print the full public key to standard output after signature verification. verify-time=timestamp Specifies a time to use when validating signatures instead of the current time. The time may be specified as a date in YYYYMMDD format or a time in YYYYMMD‐ DHHMM[SS] format. The -O option may be specified multiple times." }, { "flag": "-P", "long": null, "arg": null, "description": "Provides the (old) passphrase." }, { "flag": "-p", "long": null, "arg": null, "description": "vate key. The program will prompt for the file containing the private key, for the old passphrase, and twice for the new passphrase." }, { "flag": "-l", "long": null, "arg": null, "description": "the contents of the KRL will be printed." }, { "flag": "-q", "long": null, "arg": null, "description": "" }, { "flag": "-R", "long": null, "arg": null, "description": "Removes all keys belonging to the specified hostname (with optional port number) from a knownhosts file. This option is useful to delete hashed hosts (see the -H option above)." }, { "flag": "-r", "long": null, "arg": null, "description": "Print the SSHFP fingerprint resource record named hostname for the specified public key file." }, { "flag": "-s", "long": null, "arg": null, "description": "Certify (sign) a public key using the specified CA key. See the CERTIFICATES section for details. When generating a KRL, -s specifies a path to a CA public key file used to revoke cer‐ tificates directly by key ID or serial number. See the KEY REVOCATION LISTS section for details." }, { "flag": "-t", "long": null, "arg": null, "description": "Specifies the type of key to create. The possible values are “dsa”, “ecdsa”, “ecdsa-sk”, “ed25519”, “ed25519-sk”, or “rsa”. This flag may also be used to specify the desired signature type when signing certifi‐ cates using an RSA CA key. The available RSA signature variants are “ssh-rsa” (SHA1 signatures, not recommended), “rsa-sha2-256”, and “rsa-sha2-512” (the default)." }, { "flag": "-s", "long": null, "arg": null, "description": "ssh-agent(1). See the CERTIFICATES section for more information." }, { "flag": "-k", "long": null, "arg": null, "description": "the existing KRL rather than a new KRL being created." }, { "flag": "-V", "long": null, "arg": null, "description": "Specify a validity interval when signing a certificate. A validity interval may con‐ sist of a single time, indicating that the certificate is valid beginning now and ex‐ piring 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 “always” 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 inter‐ val in the format described in the TIME FORMATS section of sshdconfig(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 “forever” to indicate that the cer‐ tificate has no expiry 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)." }, { "flag": "-v", "long": null, "arg": null, "description": "is helpful for debugging moduli generation. Multiple -v options increase the ver‐ bosity. The maximum is 3." }, { "flag": "-w", "long": null, "arg": null, "description": "Specifies a path to a library that will be used when creating FIDO authenticator-hosted keys, overriding the default of using the internal USB HID support." }, { "flag": "-Y", "long": null, "arg": null, "description": "Find the principal(s) associated with the public key of a signature, provided using the -s flag in an authorized signers file provided using the -f flag. The format of the allowed signers file is documented in the ALLOWED SIGNERS section below. If one or more matching principals are found, they are returned on standard output." }, { "flag": "-Y", "long": null, "arg": null, "description": "Find principal matching the principal name provided using the -I flag in the authorized signers file specified using the -f flag. If one or more matching principals are found, they are returned on standard output." }, { "flag": "-Y", "long": null, "arg": null, "description": "Checks that a signature generated using ssh-keygen -Y sign has a valid structure. This does not validate if a signature comes from an authorized signer. When testing a sig‐ nature, ssh-keygen accepts a message on standard input and a signature namespace using -n. A file containing the corresponding signature must also be supplied using the -s flag. Successful testing of the signature is signalled by ssh-keygen returning a zero exit status." }, { "flag": "-Y", "long": null, "arg": null, "description": "Cryptographically sign a file or some data using a SSH key. When signing, ssh-keygen accepts zero or more files to sign on the command-line - if no files are specified then ssh-keygen will sign data presented on standard input. Signatures are written to the path of the input file with “.sig” appended, or to standard output if the message to be signed was read from standard input. The key used for signing is specified using the -f option and may refer to either a private key, or a public key with the private half available via ssh-agent(1). An ad‐ ditional signature namespace, used to prevent signature confusion across different do‐ mains of use (e.g. file signing vs email signing) must be provided via the -n flag. Namespaces are arbitrary strings, and may include: “file” for file signing, “email” for email signing. For custom uses, it is recommended to use names following a NAME‐ SPACE@YOUR.DOMAIN pattern to generate unambiguous namespaces." }, { "flag": "-Y", "long": null, "arg": null, "description": "Request to verify a signature generated using ssh-keygen -Y sign as described above. When verifying a signature, ssh-keygen accepts a message on standard input and a signa‐ ture namespace using -n. A file containing the corresponding signature must also be supplied using the -s flag, along with the identity of the signer using -I and a list of allowed signers via the -f flag. The format of the allowed signers file is docu‐ mented in the ALLOWED SIGNERS section below. A file containing revoked keys can be passed using the -r flag. The revocation file may be a KRL or a one-per-line list of public keys. Successful verification by an authorized signer is signalled by ssh-keygen returning a zero exit status." }, { "flag": "-y", "long": null, "arg": null, "description": "stdout." }, { "flag": "-Z", "long": null, "arg": null, "description": "Specifies the cipher to use for encryption when writing an OpenSSH-format private key file. The list of available ciphers may be obtained using \"ssh -Q cipher\". The de‐ fault is “aes256-ctr”." }, { "flag": "-z", "long": null, "arg": null, "description": "Specifies a serial number to be embedded in the certificate to distinguish this cer‐ tificate from others from the same CA. If the serialnumber is prefixed with a ‘+’ character, then the serial number will be incremented for each certificate signed on a single command-line. The default serial number is zero. When generating a KRL, the -z flag is used to specify a KRL version number." } ], "examples": [], "see_also": [ { "name": "ssh", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ssh/1/json" }, { "name": "ssh-add", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ssh-add/1/json" }, { "name": "ssh-agent", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/ssh-agent/1/json" }, { "name": "moduli", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/moduli/5/json" }, { "name": "sshd", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/sshd/8/json" } ], "tldr": { "source": "official", "description": "Generate SSH keys used for authentication, password-less logins, and other things.", "examples": [ { "description": "Generate a key interactively", "command": "ssh-keygen" }, { "description": "Generate an ed25519 key with 32 key derivation function rounds and save the key to a specific file", "command": "ssh-keygen -f {{~/.ssh/filename}} -t ed25519 -a 32" }, { "description": "Generate an RSA 4096-bit key with email as a comment", "command": "ssh-keygen -t rsa -b 4096 -C \"{{comment|email}}\"" }, { "description": "Remove the keys of a host from the `known_hosts` file (useful when a known host has a new key)", "command": "ssh-keygen -R {{remote_host}}" }, { "description": "Retrieve the fingerprint of a key in MD5 Hex", "command": "ssh-keygen -f {{~/.ssh/filename}} -l -E md5" }, { "description": "Change the password of a key", "command": "ssh-keygen -f {{~/.ssh/filename}} -p" }, { "description": "Change the type of the key format (for example from OPENSSH format to PEM), the file will be rewritten in-place", "command": "ssh-keygen -f {{~/.ssh/OpenSSH_private_key}} -p -m PEM" }, { "description": "Retrieve public key from private key", "command": "ssh-keygen -f {{~/.ssh/OpenSSH_private_key}} -y" } ] } }