1.\" $OpenBSD: ssh-keygen.1,v 1.130 2016/02/17 07:38:19 jmc Exp $ 2.\" 3.\" Author: Tatu Ylonen <ylo@cs.hut.fi> 4.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5.\" All rights reserved 6.\" 7.\" As far as I am concerned, the code I have written for this software 8.\" can be used freely for any purpose. Any derived versions of this 9.\" software must be clearly marked as such, and if the derived work is 10.\" incompatible with the protocol description in the RFC file, it must be 11.\" called by a name other than "ssh" or "Secure Shell". 12.\" 13.\" 14.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. 15.\" Copyright (c) 1999 Aaron Campbell. All rights reserved. 16.\" Copyright (c) 1999 Theo de Raadt. All rights reserved. 17.\" 18.\" Redistribution and use in source and binary forms, with or without 19.\" modification, are permitted provided that the following conditions 20.\" are met: 21.\" 1. Redistributions of source code must retain the above copyright 22.\" notice, this list of conditions and the following disclaimer. 23.\" 2. Redistributions in binary form must reproduce the above copyright 24.\" notice, this list of conditions and the following disclaimer in the 25.\" documentation and/or other materials provided with the distribution. 26.\" 27.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37.\" 38.Dd $Mdocdate: February 17 2016 $ 39.Dt SSH-KEYGEN 1 40.Os 41.Sh NAME 42.Nm ssh-keygen 43.Nd authentication key generation, management and conversion 44.Sh SYNOPSIS 45.Bk -words 46.Nm ssh-keygen 47.Op Fl q 48.Op Fl b Ar bits 49.Op Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1 50.Op Fl N Ar new_passphrase 51.Op Fl C Ar comment 52.Op Fl f Ar output_keyfile 53.Nm ssh-keygen 54.Fl p 55.Op Fl P Ar old_passphrase 56.Op Fl N Ar new_passphrase 57.Op Fl f Ar keyfile 58.Nm ssh-keygen 59.Fl i 60.Op Fl m Ar key_format 61.Op Fl f Ar input_keyfile 62.Nm ssh-keygen 63.Fl e 64.Op Fl m Ar key_format 65.Op Fl f Ar input_keyfile 66.Nm ssh-keygen 67.Fl y 68.Op Fl f Ar input_keyfile 69.Nm ssh-keygen 70.Fl c 71.Op Fl P Ar passphrase 72.Op Fl C Ar comment 73.Op Fl f Ar keyfile 74.Nm ssh-keygen 75.Fl l 76.Op Fl v 77.Op Fl E Ar fingerprint_hash 78.Op Fl f Ar input_keyfile 79.Nm ssh-keygen 80.Fl B 81.Op Fl f Ar input_keyfile 82.Nm ssh-keygen 83.Fl D Ar pkcs11 84.Nm ssh-keygen 85.Fl F Ar hostname 86.Op Fl f Ar known_hosts_file 87.Op Fl l 88.Nm ssh-keygen 89.Fl H 90.Op Fl f Ar known_hosts_file 91.Nm ssh-keygen 92.Fl R Ar hostname 93.Op Fl f Ar known_hosts_file 94.Nm ssh-keygen 95.Fl r Ar hostname 96.Op Fl f Ar input_keyfile 97.Op Fl g 98.Nm ssh-keygen 99.Fl G Ar output_file 100.Op Fl v 101.Op Fl b Ar bits 102.Op Fl M Ar memory 103.Op Fl S Ar start_point 104.Nm ssh-keygen 105.Fl T Ar output_file 106.Fl f Ar input_file 107.Op Fl v 108.Op Fl a Ar rounds 109.Op Fl J Ar num_lines 110.Op Fl j Ar start_line 111.Op Fl K Ar checkpt 112.Op Fl W Ar generator 113.Nm ssh-keygen 114.Fl s Ar ca_key 115.Fl I Ar certificate_identity 116.Op Fl h 117.Op Fl n Ar principals 118.Op Fl O Ar option 119.Op Fl V Ar validity_interval 120.Op Fl z Ar serial_number 121.Ar 122.Nm ssh-keygen 123.Fl L 124.Op Fl f Ar input_keyfile 125.Nm ssh-keygen 126.Fl A 127.Nm ssh-keygen 128.Fl k 129.Fl f Ar krl_file 130.Op Fl u 131.Op Fl s Ar ca_public 132.Op Fl z Ar version_number 133.Ar 134.Nm ssh-keygen 135.Fl Q 136.Fl f Ar krl_file 137.Ar 138.Ek 139.Sh DESCRIPTION 140.Nm 141generates, manages and converts authentication keys for 142.Xr ssh 1 . 143.Nm 144can create keys for use by SSH protocol versions 1 and 2. 145Protocol 1 should not be used 146and is only offered to support legacy devices. 147It suffers from a number of cryptographic weaknesses 148and doesn't support many of the advanced features available for protocol 2. 149.Pp 150The type of key to be generated is specified with the 151.Fl t 152option. 153If invoked without any arguments, 154.Nm 155will generate an RSA key for use in SSH protocol 2 connections. 156.Pp 157.Nm 158is also used to generate groups for use in Diffie-Hellman group 159exchange (DH-GEX). 160See the 161.Sx MODULI GENERATION 162section for details. 163.Pp 164Finally, 165.Nm 166can be used to generate and update Key Revocation Lists, and to test whether 167given keys have been revoked by one. 168See the 169.Sx KEY REVOCATION LISTS 170section for details. 171.Pp 172Normally each user wishing to use SSH 173with public key authentication runs this once to create the authentication 174key in 175.Pa ~/.ssh/identity , 176.Pa ~/.ssh/id_dsa , 177.Pa ~/.ssh/id_ecdsa , 178.Pa ~/.ssh/id_ed25519 179or 180.Pa ~/.ssh/id_rsa . 181Additionally, the system administrator may use this to generate host keys, 182as seen in 183.Pa /etc/rc . 184.Pp 185Normally this program generates the key and asks for a file in which 186to store the private key. 187The public key is stored in a file with the same name but 188.Dq .pub 189appended. 190The program also asks for a passphrase. 191The passphrase may be empty to indicate no passphrase 192(host keys must have an empty passphrase), or it may be a string of 193arbitrary length. 194A passphrase is similar to a password, except it can be a phrase with a 195series of words, punctuation, numbers, whitespace, or any string of 196characters you want. 197Good passphrases are 10-30 characters long, are 198not simple sentences or otherwise easily guessable (English 199prose has only 1-2 bits of entropy per character, and provides very bad 200passphrases), and contain a mix of upper and lowercase letters, 201numbers, and non-alphanumeric characters. 202The passphrase can be changed later by using the 203.Fl p 204option. 205.Pp 206There is no way to recover a lost passphrase. 207If the passphrase is lost or forgotten, a new key must be generated 208and the corresponding public key copied to other machines. 209.Pp 210For RSA1 keys, 211there is also a comment field in the key file that is only for 212convenience to the user to help identify the key. 213The comment can tell what the key is for, or whatever is useful. 214The comment is initialized to 215.Dq user@host 216when the key is created, but can be changed using the 217.Fl c 218option. 219.Pp 220After a key is generated, instructions below detail where the keys 221should be placed to be activated. 222.Pp 223The options are as follows: 224.Bl -tag -width Ds 225.It Fl A 226For each of the key types (rsa1, rsa, dsa, ecdsa and ed25519) 227for which host keys 228do not exist, generate the host keys with the default key file path, 229an empty passphrase, default bits for the key type, and default comment. 230This is used by 231.Pa /etc/rc 232to generate new host keys. 233.It Fl a Ar rounds 234When saving a new-format private key (i.e. an ed25519 key or any SSH protocol 2352 key when the 236.Fl o 237flag is set), this option specifies the number of KDF (key derivation function) 238rounds used. 239Higher numbers result in slower passphrase verification and increased 240resistance to brute-force password cracking (should the keys be stolen). 241.Pp 242When screening DH-GEX candidates ( 243using the 244.Fl T 245command). 246This option specifies the number of primality tests to perform. 247.It Fl B 248Show the bubblebabble digest of specified private or public key file. 249.It Fl b Ar bits 250Specifies the number of bits in the key to create. 251For RSA keys, the minimum size is 1024 bits and the default is 2048 bits. 252Generally, 2048 bits is considered sufficient. 253DSA keys must be exactly 1024 bits as specified by FIPS 186-2. 254For ECDSA keys, the 255.Fl b 256flag determines the key length by selecting from one of three elliptic 257curve sizes: 256, 384 or 521 bits. 258Attempting to use bit lengths other than these three values for ECDSA keys 259will fail. 260Ed25519 keys have a fixed length and the 261.Fl b 262flag will be ignored. 263.It Fl C Ar comment 264Provides a new comment. 265.It Fl c 266Requests changing the comment in the private and public key files. 267This operation is only supported for RSA1 keys. 268The program will prompt for the file containing the private keys, for 269the passphrase if the key has one, and for the new comment. 270.It Fl D Ar pkcs11 271Download the RSA public keys provided by the PKCS#11 shared library 272.Ar pkcs11 . 273When used in combination with 274.Fl s , 275this option indicates that a CA key resides in a PKCS#11 token (see the 276.Sx CERTIFICATES 277section for details). 278.It Fl E Ar fingerprint_hash 279Specifies the hash algorithm used when displaying key fingerprints. 280Valid options are: 281.Dq md5 282and 283.Dq sha256 . 284The default is 285.Dq sha256 . 286.It Fl e 287This option will read a private or public OpenSSH key file and 288print to stdout the key in one of the formats specified by the 289.Fl m 290option. 291The default export format is 292.Dq RFC4716 . 293This option allows exporting OpenSSH keys for use by other programs, including 294several commercial SSH implementations. 295.It Fl F Ar hostname 296Search for the specified 297.Ar hostname 298in a 299.Pa known_hosts 300file, listing any occurrences found. 301This option is useful to find hashed host names or addresses and may also be 302used in conjunction with the 303.Fl H 304option to print found keys in a hashed format. 305.It Fl f Ar filename 306Specifies the filename of the key file. 307.It Fl G Ar output_file 308Generate candidate primes for DH-GEX. 309These primes must be screened for 310safety (using the 311.Fl T 312option) before use. 313.It Fl g 314Use generic DNS format when printing fingerprint resource records using the 315.Fl r 316command. 317.It Fl H 318Hash a 319.Pa known_hosts 320file. 321This replaces all hostnames and addresses with hashed representations 322within the specified file; the original content is moved to a file with 323a .old suffix. 324These hashes may be used normally by 325.Nm ssh 326and 327.Nm sshd , 328but they do not reveal identifying information should the file's contents 329be disclosed. 330This option will not modify existing hashed hostnames and is therefore safe 331to use on files that mix hashed and non-hashed names. 332.It Fl h 333When signing a key, create a host certificate instead of a user 334certificate. 335Please see the 336.Sx CERTIFICATES 337section for details. 338.It Fl I Ar certificate_identity 339Specify the key identity when signing a public key. 340Please see the 341.Sx CERTIFICATES 342section for details. 343.It Fl i 344This option will read an unencrypted private (or public) key file 345in the format specified by the 346.Fl m 347option and print an OpenSSH compatible private 348(or public) key to stdout. 349This option allows importing keys from other software, including several 350commercial SSH implementations. 351The default import format is 352.Dq RFC4716 . 353.It Fl J Ar num_lines 354Exit after screening the specified number of lines 355while performing DH candidate screening using the 356.Fl T 357option. 358.It Fl j Ar start_line 359Start screening at the specified line number 360while performing DH candidate screening using the 361.Fl T 362option. 363.It Fl K Ar checkpt 364Write the last line processed to the file 365.Ar checkpt 366while performing DH candidate screening using the 367.Fl T 368option. 369This will be used to skip lines in the input file that have already been 370processed if the job is restarted. 371.It Fl k 372Generate a KRL file. 373In this mode, 374.Nm 375will generate a KRL file at the location specified via the 376.Fl f 377flag that revokes every key or certificate presented on the command line. 378Keys/certificates to be revoked may be specified by public key file or 379using the format described in the 380.Sx KEY REVOCATION LISTS 381section. 382.It Fl L 383Prints the contents of one or more certificates. 384.It Fl l 385Show fingerprint of specified public key file. 386Private RSA1 keys are also supported. 387For RSA and DSA keys 388.Nm 389tries to find the matching public key file and prints its fingerprint. 390If combined with 391.Fl v , 392an ASCII art representation of the key is supplied with the fingerprint. 393.It Fl M Ar memory 394Specify the amount of memory to use (in megabytes) when generating 395candidate moduli for DH-GEX. 396.It Fl m Ar key_format 397Specify a key format for the 398.Fl i 399(import) or 400.Fl e 401(export) conversion options. 402The supported key formats are: 403.Dq RFC4716 404(RFC 4716/SSH2 public or private key), 405.Dq PKCS8 406(PEM PKCS8 public key) 407or 408.Dq PEM 409(PEM public key). 410The default conversion format is 411.Dq RFC4716 . 412.It Fl N Ar new_passphrase 413Provides the new passphrase. 414.It Fl n Ar principals 415Specify one or more principals (user or host names) to be included in 416a certificate when signing a key. 417Multiple principals may be specified, separated by commas. 418Please see the 419.Sx CERTIFICATES 420section for details. 421.It Fl O Ar option 422Specify a certificate option when signing a key. 423This option may be specified multiple times. 424Please see the 425.Sx CERTIFICATES 426section for details. 427The options that are valid for user certificates are: 428.Bl -tag -width Ds 429.It Ic clear 430Clear all enabled permissions. 431This is useful for clearing the default set of permissions so permissions may 432be added individually. 433.It Ic force-command Ns = Ns Ar command 434Forces the execution of 435.Ar command 436instead of any shell or command specified by the user when 437the certificate is used for authentication. 438.It Ic no-agent-forwarding 439Disable 440.Xr ssh-agent 1 441forwarding (permitted by default). 442.It Ic no-port-forwarding 443Disable port forwarding (permitted by default). 444.It Ic no-pty 445Disable PTY allocation (permitted by default). 446.It Ic no-user-rc 447Disable execution of 448.Pa ~/.ssh/rc 449by 450.Xr sshd 8 451(permitted by default). 452.It Ic no-x11-forwarding 453Disable X11 forwarding (permitted by default). 454.It Ic permit-agent-forwarding 455Allows 456.Xr ssh-agent 1 457forwarding. 458.It Ic permit-port-forwarding 459Allows port forwarding. 460.It Ic permit-pty 461Allows PTY allocation. 462.It Ic permit-user-rc 463Allows execution of 464.Pa ~/.ssh/rc 465by 466.Xr sshd 8 . 467.It Ic permit-x11-forwarding 468Allows X11 forwarding. 469.It Ic source-address Ns = Ns Ar address_list 470Restrict the source addresses from which the certificate is considered valid. 471The 472.Ar address_list 473is a comma-separated list of one or more address/netmask pairs in CIDR 474format. 475.El 476.Pp 477At present, no options are valid for host keys. 478.It Fl o 479Causes 480.Nm 481to save private keys using the new OpenSSH format rather than 482the more compatible PEM format. 483The new format has increased resistance to brute-force password cracking 484but is not supported by versions of OpenSSH prior to 6.5. 485Ed25519 keys always use the new private key format. 486.It Fl P Ar passphrase 487Provides the (old) passphrase. 488.It Fl p 489Requests changing the passphrase of a private key file instead of 490creating a new private key. 491The program will prompt for the file 492containing the private key, for the old passphrase, and twice for the 493new passphrase. 494.It Fl Q 495Test whether keys have been revoked in a KRL. 496.It Fl q 497Silence 498.Nm ssh-keygen . 499.It Fl R Ar hostname 500Removes all keys belonging to 501.Ar hostname 502from a 503.Pa known_hosts 504file. 505This option is useful to delete hashed hosts (see the 506.Fl H 507option above). 508.It Fl r Ar hostname 509Print the SSHFP fingerprint resource record named 510.Ar hostname 511for the specified public key file. 512.It Fl S Ar start 513Specify start point (in hex) when generating candidate moduli for DH-GEX. 514.It Fl s Ar ca_key 515Certify (sign) a public key using the specified CA key. 516Please see the 517.Sx CERTIFICATES 518section for details. 519.Pp 520When generating a KRL, 521.Fl s 522specifies a path to a CA public key file used to revoke certificates directly 523by key ID or serial number. 524See the 525.Sx KEY REVOCATION LISTS 526section for details. 527.It Fl T Ar output_file 528Test DH group exchange candidate primes (generated using the 529.Fl G 530option) for safety. 531.It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1 532Specifies the type of key to create. 533The possible values are 534.Dq rsa1 535for protocol version 1 and 536.Dq dsa , 537.Dq ecdsa , 538.Dq ed25519 , 539or 540.Dq rsa 541for protocol version 2. 542.It Fl u 543Update a KRL. 544When specified with 545.Fl k , 546keys listed via the command line are added to the existing KRL rather than 547a new KRL being created. 548.It Fl V Ar validity_interval 549Specify a validity interval when signing a certificate. 550A validity interval may consist of a single time, indicating that the 551certificate is valid beginning now and expiring at that time, or may consist 552of two times separated by a colon to indicate an explicit time interval. 553The start time may be specified as a date in YYYYMMDD format, a time 554in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting 555of a minus sign followed by a relative time in the format described in the 556TIME FORMATS section of 557.Xr sshd_config 5 . 558The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or 559a relative time starting with a plus character. 560.Pp 561For example: 562.Dq +52w1d 563(valid from now to 52 weeks and one day from now), 564.Dq -4w:+4w 565(valid from four weeks ago to four weeks from now), 566.Dq 20100101123000:20110101123000 567(valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), 568.Dq -1d:20110101 569(valid from yesterday to midnight, January 1st, 2011). 570.It Fl v 571Verbose mode. 572Causes 573.Nm 574to print debugging messages about its progress. 575This is helpful for debugging moduli generation. 576Multiple 577.Fl v 578options increase the verbosity. 579The maximum is 3. 580.It Fl W Ar generator 581Specify desired generator when testing candidate moduli for DH-GEX. 582.It Fl y 583This option will read a private 584OpenSSH format file and print an OpenSSH public key to stdout. 585.It Fl z Ar serial_number 586Specifies a serial number to be embedded in the certificate to distinguish 587this certificate from others from the same CA. 588The default serial number is zero. 589.Pp 590When generating a KRL, the 591.Fl z 592flag is used to specify a KRL version number. 593.El 594.Sh MODULI GENERATION 595.Nm 596may be used to generate groups for the Diffie-Hellman Group Exchange 597(DH-GEX) protocol. 598Generating these groups is a two-step process: first, candidate 599primes are generated using a fast, but memory intensive process. 600These candidate primes are then tested for suitability (a CPU-intensive 601process). 602.Pp 603Generation of primes is performed using the 604.Fl G 605option. 606The desired length of the primes may be specified by the 607.Fl b 608option. 609For example: 610.Pp 611.Dl # ssh-keygen -G moduli-2048.candidates -b 2048 612.Pp 613By default, the search for primes begins at a random point in the 614desired length range. 615This may be overridden using the 616.Fl S 617option, which specifies a different start point (in hex). 618.Pp 619Once a set of candidates have been generated, they must be screened for 620suitability. 621This may be performed using the 622.Fl T 623option. 624In this mode 625.Nm 626will read candidates from standard input (or a file specified using the 627.Fl f 628option). 629For example: 630.Pp 631.Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates 632.Pp 633By default, each candidate will be subjected to 100 primality tests. 634This may be overridden using the 635.Fl a 636option. 637The DH generator value will be chosen automatically for the 638prime under consideration. 639If a specific generator is desired, it may be requested using the 640.Fl W 641option. 642Valid generator values are 2, 3, and 5. 643.Pp 644Screened DH groups may be installed in 645.Pa /etc/moduli . 646It is important that this file contains moduli of a range of bit lengths and 647that both ends of a connection share common moduli. 648.Sh CERTIFICATES 649.Nm 650supports signing of keys to produce certificates that may be used for 651user or host authentication. 652Certificates consist of a public key, some identity information, zero or 653more principal (user or host) names and a set of options that 654are signed by a Certification Authority (CA) key. 655Clients or servers may then trust only the CA key and verify its signature 656on a certificate rather than trusting many user/host keys. 657Note that OpenSSH certificates are a different, and much simpler, format to 658the X.509 certificates used in 659.Xr ssl 8 . 660.Pp 661.Nm 662supports two types of certificates: user and host. 663User certificates authenticate users to servers, whereas host certificates 664authenticate server hosts to users. 665To generate a user certificate: 666.Pp 667.Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub 668.Pp 669The resultant certificate will be placed in 670.Pa /path/to/user_key-cert.pub . 671A host certificate requires the 672.Fl h 673option: 674.Pp 675.Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub 676.Pp 677The host certificate will be output to 678.Pa /path/to/host_key-cert.pub . 679.Pp 680It is possible to sign using a CA key stored in a PKCS#11 token by 681providing the token library using 682.Fl D 683and identifying the CA key by providing its public half as an argument 684to 685.Fl s : 686.Pp 687.Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub 688.Pp 689In all cases, 690.Ar key_id 691is a "key identifier" that is logged by the server when the certificate 692is used for authentication. 693.Pp 694Certificates may be limited to be valid for a set of principal (user/host) 695names. 696By default, generated certificates are valid for all users or hosts. 697To generate a certificate for a specified set of principals: 698.Pp 699.Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub 700.Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub" 701.Pp 702Additional limitations on the validity and use of user certificates may 703be specified through certificate options. 704A certificate option may disable features of the SSH session, may be 705valid only when presented from particular source addresses or may 706force the use of a specific command. 707For a list of valid certificate options, see the documentation for the 708.Fl O 709option above. 710.Pp 711Finally, certificates may be defined with a validity lifetime. 712The 713.Fl V 714option allows specification of certificate start and end times. 715A certificate that is presented at a time outside this range will not be 716considered valid. 717By default, certificates are valid from 718.Ux 719Epoch to the distant future. 720.Pp 721For certificates to be used for user or host authentication, the CA 722public key must be trusted by 723.Xr sshd 8 724or 725.Xr ssh 1 . 726Please refer to those manual pages for details. 727.Sh KEY REVOCATION LISTS 728.Nm 729is able to manage OpenSSH format Key Revocation Lists (KRLs). 730These binary files specify keys or certificates to be revoked using a 731compact format, taking as little as one bit per certificate if they are being 732revoked by serial number. 733.Pp 734KRLs may be generated using the 735.Fl k 736flag. 737This option reads one or more files from the command line and generates a new 738KRL. 739The files may either contain a KRL specification (see below) or public keys, 740listed one per line. 741Plain public keys are revoked by listing their hash or contents in the KRL and 742certificates revoked by serial number or key ID (if the serial is zero or 743not available). 744.Pp 745Revoking keys using a KRL specification offers explicit control over the 746types of record used to revoke keys and may be used to directly revoke 747certificates by serial number or key ID without having the complete original 748certificate on hand. 749A KRL specification consists of lines containing one of the following directives 750followed by a colon and some directive-specific information. 751.Bl -tag -width Ds 752.It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number 753Revokes a certificate with the specified serial number. 754Serial numbers are 64-bit values, not including zero and may be expressed 755in decimal, hex or octal. 756If two serial numbers are specified separated by a hyphen, then the range 757of serial numbers including and between each is revoked. 758The CA key must have been specified on the 759.Nm 760command line using the 761.Fl s 762option. 763.It Cm id : Ar key_id 764Revokes a certificate with the specified key ID string. 765The CA key must have been specified on the 766.Nm 767command line using the 768.Fl s 769option. 770.It Cm key : Ar public_key 771Revokes the specified key. 772If a certificate is listed, then it is revoked as a plain public key. 773.It Cm sha1 : Ar public_key 774Revokes the specified key by its SHA1 hash. 775.El 776.Pp 777KRLs may be updated using the 778.Fl u 779flag in addition to 780.Fl k . 781When this option is specified, keys listed via the command line are merged into 782the KRL, adding to those already there. 783.Pp 784It is also possible, given a KRL, to test whether it revokes a particular key 785(or keys). 786The 787.Fl Q 788flag will query an existing KRL, testing each key specified on the command line. 789If any key listed on the command line has been revoked (or an error encountered) 790then 791.Nm 792will exit with a non-zero exit status. 793A zero exit status will only be returned if no key was revoked. 794.Sh FILES 795.Bl -tag -width Ds -compact 796.It Pa ~/.ssh/identity 797Contains the protocol version 1 RSA authentication identity of the user. 798This file should not be readable by anyone but the user. 799It is possible to 800specify a passphrase when generating the key; that passphrase will be 801used to encrypt the private part of this file using 3DES. 802This file is not automatically accessed by 803.Nm 804but it is offered as the default file for the private key. 805.Xr ssh 1 806will read this file when a login attempt is made. 807.Pp 808.It Pa ~/.ssh/identity.pub 809Contains the protocol version 1 RSA public key for authentication. 810The contents of this file should be added to 811.Pa ~/.ssh/authorized_keys 812on all machines 813where the user wishes to log in using RSA authentication. 814There is no need to keep the contents of this file secret. 815.Pp 816.It Pa ~/.ssh/id_dsa 817.It Pa ~/.ssh/id_ecdsa 818.It Pa ~/.ssh/id_ed25519 819.It Pa ~/.ssh/id_rsa 820Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA 821authentication identity of the user. 822This file should not be readable by anyone but the user. 823It is possible to 824specify a passphrase when generating the key; that passphrase will be 825used to encrypt the private part of this file using 128-bit AES. 826This file is not automatically accessed by 827.Nm 828but it is offered as the default file for the private key. 829.Xr ssh 1 830will read this file when a login attempt is made. 831.Pp 832.It Pa ~/.ssh/id_dsa.pub 833.It Pa ~/.ssh/id_ecdsa.pub 834.It Pa ~/.ssh/id_ed25519.pub 835.It Pa ~/.ssh/id_rsa.pub 836Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA 837public key for authentication. 838The contents of this file should be added to 839.Pa ~/.ssh/authorized_keys 840on all machines 841where the user wishes to log in using public key authentication. 842There is no need to keep the contents of this file secret. 843.Pp 844.It Pa /etc/moduli 845Contains Diffie-Hellman groups used for DH-GEX. 846The file format is described in 847.Xr moduli 5 . 848.El 849.Sh SEE ALSO 850.Xr ssh 1 , 851.Xr ssh-add 1 , 852.Xr ssh-agent 1 , 853.Xr moduli 5 , 854.Xr sshd 8 855.Rs 856.%R RFC 4716 857.%T "The Secure Shell (SSH) Public Key File Format" 858.%D 2006 859.Re 860.Sh AUTHORS 861OpenSSH is a derivative of the original and free 862ssh 1.2.12 release by Tatu Ylonen. 863Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, 864Theo de Raadt and Dug Song 865removed many bugs, re-added newer features and 866created OpenSSH. 867Markus Friedl contributed the support for SSH 868protocol versions 1.5 and 2.0. 869