1.\" $OpenBSD: ssh-keygen.1,v 1.132 2016/05/03 18:38:12 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: May 3 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 , 392a visual ASCII art representation of the key is supplied with the 393fingerprint. 394.It Fl M Ar memory 395Specify the amount of memory to use (in megabytes) when generating 396candidate moduli for DH-GEX. 397.It Fl m Ar key_format 398Specify a key format for the 399.Fl i 400(import) or 401.Fl e 402(export) conversion options. 403The supported key formats are: 404.Dq RFC4716 405(RFC 4716/SSH2 public or private key), 406.Dq PKCS8 407(PEM PKCS8 public key) 408or 409.Dq PEM 410(PEM public key). 411The default conversion format is 412.Dq RFC4716 . 413.It Fl N Ar new_passphrase 414Provides the new passphrase. 415.It Fl n Ar principals 416Specify one or more principals (user or host names) to be included in 417a certificate when signing a key. 418Multiple principals may be specified, separated by commas. 419Please see the 420.Sx CERTIFICATES 421section for details. 422.It Fl O Ar option 423Specify a certificate option when signing a key. 424This option may be specified multiple times. 425Please see the 426.Sx CERTIFICATES 427section for details. 428The options that are valid for user certificates are: 429.Bl -tag -width Ds 430.It Ic clear 431Clear all enabled permissions. 432This is useful for clearing the default set of permissions so permissions may 433be added individually. 434.It Ic force-command Ns = Ns Ar command 435Forces the execution of 436.Ar command 437instead of any shell or command specified by the user when 438the certificate is used for authentication. 439.It Ic no-agent-forwarding 440Disable 441.Xr ssh-agent 1 442forwarding (permitted by default). 443.It Ic no-port-forwarding 444Disable port forwarding (permitted by default). 445.It Ic no-pty 446Disable PTY allocation (permitted by default). 447.It Ic no-user-rc 448Disable execution of 449.Pa ~/.ssh/rc 450by 451.Xr sshd 8 452(permitted by default). 453.It Ic no-x11-forwarding 454Disable X11 forwarding (permitted by default). 455.It Ic permit-agent-forwarding 456Allows 457.Xr ssh-agent 1 458forwarding. 459.It Ic permit-port-forwarding 460Allows port forwarding. 461.It Ic permit-pty 462Allows PTY allocation. 463.It Ic permit-user-rc 464Allows execution of 465.Pa ~/.ssh/rc 466by 467.Xr sshd 8 . 468.It Ic permit-x11-forwarding 469Allows X11 forwarding. 470.It Ic source-address Ns = Ns Ar address_list 471Restrict the source addresses from which the certificate is considered valid. 472The 473.Ar address_list 474is a comma-separated list of one or more address/netmask pairs in CIDR 475format. 476.El 477.Pp 478At present, no options are valid for host keys. 479.It Fl o 480Causes 481.Nm 482to save private keys using the new OpenSSH format rather than 483the more compatible PEM format. 484The new format has increased resistance to brute-force password cracking 485but is not supported by versions of OpenSSH prior to 6.5. 486Ed25519 keys always use the new private key format. 487.It Fl P Ar passphrase 488Provides the (old) passphrase. 489.It Fl p 490Requests changing the passphrase of a private key file instead of 491creating a new private key. 492The program will prompt for the file 493containing the private key, for the old passphrase, and twice for the 494new passphrase. 495.It Fl Q 496Test whether keys have been revoked in a KRL. 497.It Fl q 498Silence 499.Nm ssh-keygen . 500.It Fl R Ar hostname 501Removes all keys belonging to 502.Ar hostname 503from a 504.Pa known_hosts 505file. 506This option is useful to delete hashed hosts (see the 507.Fl H 508option above). 509.It Fl r Ar hostname 510Print the SSHFP fingerprint resource record named 511.Ar hostname 512for the specified public key file. 513.It Fl S Ar start 514Specify start point (in hex) when generating candidate moduli for DH-GEX. 515.It Fl s Ar ca_key 516Certify (sign) a public key using the specified CA key. 517Please see the 518.Sx CERTIFICATES 519section for details. 520.Pp 521When generating a KRL, 522.Fl s 523specifies a path to a CA public key file used to revoke certificates directly 524by key ID or serial number. 525See the 526.Sx KEY REVOCATION LISTS 527section for details. 528.It Fl T Ar output_file 529Test DH group exchange candidate primes (generated using the 530.Fl G 531option) for safety. 532.It Fl t Cm dsa | ecdsa | ed25519 | rsa | rsa1 533Specifies the type of key to create. 534The possible values are 535.Dq rsa1 536for protocol version 1 and 537.Dq dsa , 538.Dq ecdsa , 539.Dq ed25519 , 540or 541.Dq rsa 542for protocol version 2. 543.It Fl u 544Update a KRL. 545When specified with 546.Fl k , 547keys listed via the command line are added to the existing KRL rather than 548a new KRL being created. 549.It Fl V Ar validity_interval 550Specify a validity interval when signing a certificate. 551A validity interval may consist of a single time, indicating that the 552certificate is valid beginning now and expiring at that time, or may consist 553of two times separated by a colon to indicate an explicit time interval. 554The start time may be specified as a date in YYYYMMDD format, a time 555in YYYYMMDDHHMMSS format or a relative time (to the current time) consisting 556of a minus sign followed by a relative time in the format described in the 557TIME FORMATS section of 558.Xr sshd_config 5 . 559The end time may be specified as a YYYYMMDD date, a YYYYMMDDHHMMSS time or 560a relative time starting with a plus character. 561.Pp 562For example: 563.Dq +52w1d 564(valid from now to 52 weeks and one day from now), 565.Dq -4w:+4w 566(valid from four weeks ago to four weeks from now), 567.Dq 20100101123000:20110101123000 568(valid from 12:30 PM, January 1st, 2010 to 12:30 PM, January 1st, 2011), 569.Dq -1d:20110101 570(valid from yesterday to midnight, January 1st, 2011). 571.It Fl v 572Verbose mode. 573Causes 574.Nm 575to print debugging messages about its progress. 576This is helpful for debugging moduli generation. 577Multiple 578.Fl v 579options increase the verbosity. 580The maximum is 3. 581.It Fl W Ar generator 582Specify desired generator when testing candidate moduli for DH-GEX. 583.It Fl y 584This option will read a private 585OpenSSH format file and print an OpenSSH public key to stdout. 586.It Fl z Ar serial_number 587Specifies a serial number to be embedded in the certificate to distinguish 588this certificate from others from the same CA. 589The default serial number is zero. 590.Pp 591When generating a KRL, the 592.Fl z 593flag is used to specify a KRL version number. 594.El 595.Sh MODULI GENERATION 596.Nm 597may be used to generate groups for the Diffie-Hellman Group Exchange 598(DH-GEX) protocol. 599Generating these groups is a two-step process: first, candidate 600primes are generated using a fast, but memory intensive process. 601These candidate primes are then tested for suitability (a CPU-intensive 602process). 603.Pp 604Generation of primes is performed using the 605.Fl G 606option. 607The desired length of the primes may be specified by the 608.Fl b 609option. 610For example: 611.Pp 612.Dl # ssh-keygen -G moduli-2048.candidates -b 2048 613.Pp 614By default, the search for primes begins at a random point in the 615desired length range. 616This may be overridden using the 617.Fl S 618option, which specifies a different start point (in hex). 619.Pp 620Once a set of candidates have been generated, they must be screened for 621suitability. 622This may be performed using the 623.Fl T 624option. 625In this mode 626.Nm 627will read candidates from standard input (or a file specified using the 628.Fl f 629option). 630For example: 631.Pp 632.Dl # ssh-keygen -T moduli-2048 -f moduli-2048.candidates 633.Pp 634By default, each candidate will be subjected to 100 primality tests. 635This may be overridden using the 636.Fl a 637option. 638The DH generator value will be chosen automatically for the 639prime under consideration. 640If a specific generator is desired, it may be requested using the 641.Fl W 642option. 643Valid generator values are 2, 3, and 5. 644.Pp 645Screened DH groups may be installed in 646.Pa /etc/moduli . 647It is important that this file contains moduli of a range of bit lengths and 648that both ends of a connection share common moduli. 649.Sh CERTIFICATES 650.Nm 651supports signing of keys to produce certificates that may be used for 652user or host authentication. 653Certificates consist of a public key, some identity information, zero or 654more principal (user or host) names and a set of options that 655are signed by a Certification Authority (CA) key. 656Clients or servers may then trust only the CA key and verify its signature 657on a certificate rather than trusting many user/host keys. 658Note that OpenSSH certificates are a different, and much simpler, format to 659the X.509 certificates used in 660.Xr ssl 8 . 661.Pp 662.Nm 663supports two types of certificates: user and host. 664User certificates authenticate users to servers, whereas host certificates 665authenticate server hosts to users. 666To generate a user certificate: 667.Pp 668.Dl $ ssh-keygen -s /path/to/ca_key -I key_id /path/to/user_key.pub 669.Pp 670The resultant certificate will be placed in 671.Pa /path/to/user_key-cert.pub . 672A host certificate requires the 673.Fl h 674option: 675.Pp 676.Dl $ ssh-keygen -s /path/to/ca_key -I key_id -h /path/to/host_key.pub 677.Pp 678The host certificate will be output to 679.Pa /path/to/host_key-cert.pub . 680.Pp 681It is possible to sign using a CA key stored in a PKCS#11 token by 682providing the token library using 683.Fl D 684and identifying the CA key by providing its public half as an argument 685to 686.Fl s : 687.Pp 688.Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub 689.Pp 690In all cases, 691.Ar key_id 692is a "key identifier" that is logged by the server when the certificate 693is used for authentication. 694.Pp 695Certificates may be limited to be valid for a set of principal (user/host) 696names. 697By default, generated certificates are valid for all users or hosts. 698To generate a certificate for a specified set of principals: 699.Pp 700.Dl $ ssh-keygen -s ca_key -I key_id -n user1,user2 user_key.pub 701.Dl "$ ssh-keygen -s ca_key -I key_id -h -n host.domain host_key.pub" 702.Pp 703Additional limitations on the validity and use of user certificates may 704be specified through certificate options. 705A certificate option may disable features of the SSH session, may be 706valid only when presented from particular source addresses or may 707force the use of a specific command. 708For a list of valid certificate options, see the documentation for the 709.Fl O 710option above. 711.Pp 712Finally, certificates may be defined with a validity lifetime. 713The 714.Fl V 715option allows specification of certificate start and end times. 716A certificate that is presented at a time outside this range will not be 717considered valid. 718By default, certificates are valid from 719.Ux 720Epoch to the distant future. 721.Pp 722For certificates to be used for user or host authentication, the CA 723public key must be trusted by 724.Xr sshd 8 725or 726.Xr ssh 1 . 727Please refer to those manual pages for details. 728.Sh KEY REVOCATION LISTS 729.Nm 730is able to manage OpenSSH format Key Revocation Lists (KRLs). 731These binary files specify keys or certificates to be revoked using a 732compact format, taking as little as one bit per certificate if they are being 733revoked by serial number. 734.Pp 735KRLs may be generated using the 736.Fl k 737flag. 738This option reads one or more files from the command line and generates a new 739KRL. 740The files may either contain a KRL specification (see below) or public keys, 741listed one per line. 742Plain public keys are revoked by listing their hash or contents in the KRL and 743certificates revoked by serial number or key ID (if the serial is zero or 744not available). 745.Pp 746Revoking keys using a KRL specification offers explicit control over the 747types of record used to revoke keys and may be used to directly revoke 748certificates by serial number or key ID without having the complete original 749certificate on hand. 750A KRL specification consists of lines containing one of the following directives 751followed by a colon and some directive-specific information. 752.Bl -tag -width Ds 753.It Cm serial : Ar serial_number Ns Op - Ns Ar serial_number 754Revokes a certificate with the specified serial number. 755Serial numbers are 64-bit values, not including zero and may be expressed 756in decimal, hex or octal. 757If two serial numbers are specified separated by a hyphen, then the range 758of serial numbers including and between each is revoked. 759The CA key must have been specified on the 760.Nm 761command line using the 762.Fl s 763option. 764.It Cm id : Ar key_id 765Revokes a certificate with the specified key ID string. 766The CA key must have been specified on the 767.Nm 768command line using the 769.Fl s 770option. 771.It Cm key : Ar public_key 772Revokes the specified key. 773If a certificate is listed, then it is revoked as a plain public key. 774.It Cm sha1 : Ar public_key 775Revokes the specified key by its SHA1 hash. 776.El 777.Pp 778KRLs may be updated using the 779.Fl u 780flag in addition to 781.Fl k . 782When this option is specified, keys listed via the command line are merged into 783the KRL, adding to those already there. 784.Pp 785It is also possible, given a KRL, to test whether it revokes a particular key 786(or keys). 787The 788.Fl Q 789flag will query an existing KRL, testing each key specified on the command line. 790If any key listed on the command line has been revoked (or an error encountered) 791then 792.Nm 793will exit with a non-zero exit status. 794A zero exit status will only be returned if no key was revoked. 795.Sh FILES 796.Bl -tag -width Ds -compact 797.It Pa ~/.ssh/identity 798Contains the protocol version 1 RSA authentication identity of the user. 799This file should not be readable by anyone but the user. 800It is possible to 801specify a passphrase when generating the key; that passphrase will be 802used to encrypt the private part of this file using 3DES. 803This file is not automatically accessed by 804.Nm 805but it is offered as the default file for the private key. 806.Xr ssh 1 807will read this file when a login attempt is made. 808.Pp 809.It Pa ~/.ssh/identity.pub 810Contains the protocol version 1 RSA public key for authentication. 811The contents of this file should be added to 812.Pa ~/.ssh/authorized_keys 813on all machines 814where the user wishes to log in using RSA authentication. 815There is no need to keep the contents of this file secret. 816.Pp 817.It Pa ~/.ssh/id_dsa 818.It Pa ~/.ssh/id_ecdsa 819.It Pa ~/.ssh/id_ed25519 820.It Pa ~/.ssh/id_rsa 821Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA 822authentication identity of the user. 823This file should not be readable by anyone but the user. 824It is possible to 825specify a passphrase when generating the key; that passphrase will be 826used to encrypt the private part of this file using 128-bit AES. 827This file is not automatically accessed by 828.Nm 829but it is offered as the default file for the private key. 830.Xr ssh 1 831will read this file when a login attempt is made. 832.Pp 833.It Pa ~/.ssh/id_dsa.pub 834.It Pa ~/.ssh/id_ecdsa.pub 835.It Pa ~/.ssh/id_ed25519.pub 836.It Pa ~/.ssh/id_rsa.pub 837Contains the protocol version 2 DSA, ECDSA, Ed25519 or RSA 838public key for authentication. 839The contents of this file should be added to 840.Pa ~/.ssh/authorized_keys 841on all machines 842where the user wishes to log in using public key authentication. 843There is no need to keep the contents of this file secret. 844.Pp 845.It Pa /etc/moduli 846Contains Diffie-Hellman groups used for DH-GEX. 847The file format is described in 848.Xr moduli 5 . 849.El 850.Sh SEE ALSO 851.Xr ssh 1 , 852.Xr ssh-add 1 , 853.Xr ssh-agent 1 , 854.Xr moduli 5 , 855.Xr sshd 8 856.Rs 857.%R RFC 4716 858.%T "The Secure Shell (SSH) Public Key File Format" 859.%D 2006 860.Re 861.Sh AUTHORS 862OpenSSH is a derivative of the original and free 863ssh 1.2.12 release by Tatu Ylonen. 864Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, 865Theo de Raadt and Dug Song 866removed many bugs, re-added newer features and 867created OpenSSH. 868Markus Friedl contributed the support for SSH 869protocol versions 1.5 and 2.0. 870