SSH-KEYGEN(1)              OpenBSD Reference Manual              SSH-KEYGEN(1)NAME     ssh-keygen - authentication key generation, management and conversionSYNOPSIS     ssh-keygen [-q] [-b bits] -t type [-N new_passphrase] [-C comment]                [-f output_keyfile]     ssh-keygen -p [-P old_passphrase] [-N new_passphrase] [-f keyfile]     ssh-keygen -i [-f input_keyfile]     ssh-keygen -e [-f input_keyfile]     ssh-keygen -y [-f input_keyfile]     ssh-keygen -c [-P passphrase] [-C comment] [-f keyfile]     ssh-keygen -l [-f input_keyfile]     ssh-keygen -B [-f input_keyfile]     ssh-keygen -D reader     ssh-keygen -F hostname [-f known_hosts_file]     ssh-keygen -H [-f known_hosts_file]     ssh-keygen -R hostname [-f known_hosts_file]     ssh-keygen -U reader [-f input_keyfile]     ssh-keygen -r hostname [-f input_keyfile] [-g]     ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point]     ssh-keygen -T output_file -f input_file [-v] [-a num_trials] [-W                generator]DESCRIPTION     ssh-keygen generates, manages and converts authentication keys for     ssh(1).  ssh-keygen can create RSA keys for use by SSH protocol version 1     and RSA or DSA keys for use by SSH protocol version 2.  The type of key     to be generated is specified with the -t option.     ssh-keygen is also used to generate groups for use in Diffie-Hellman     group exchange (DH-GEX).  See the MODULI GENERATION section for details.     Normally each user wishing to use SSH with RSA or DSA authentication runs     this once to create the authentication key in $HOME/.ssh/identity,     $HOME/.ssh/id_dsa or $HOME/.ssh/id_rsa.  Additionally, the system admin-     istrator may use this to generate host keys, as seen in /etc/rc.     Normally this program generates the key and asks for a file in which to     store the private key.  The public key is stored in a file with the same     name but ``.pub'' appended.  The program also asks for a passphrase.  The     passphrase may be empty to indicate no passphrase (host keys must have an     empty passphrase), or it may be a string of arbitrary length.  A     passphrase is similar to a password, except it can be a phrase with a se-     ries of words, punctuation, numbers, whitespace, or any string of charac-     ters you want.  Good passphrases are 10-30 characters long, are not sim-     ple sentences or otherwise easily guessable (English prose has only 1-2     bits of entropy per character, and provides very bad passphrases), and     contain a mix of upper and lowercase letters, numbers, and non-alphanu-     meric characters.  The passphrase can be changed later by using the -p     option.     There is no way to recover a lost passphrase.  If the passphrase is lost     or forgotten, a new key must be generated and copied to the corresponding     public key to other machines.     For RSA1 keys, there is also a comment field in the key file that is only     for convenience to the user to help identify the key.  The comment can     tell what the key is for, or whatever is useful.  The comment is initial-     ized to ``user@host'' when the key is created, but can be changed using     the -c option.     After a key is generated, instructions below detail where the keys should     be placed to be activated.     The options are as follows:     -a trials             Specifies the number of primality tests to perform when screening             DH-GEX candidates using the -T command.     -B      Show the bubblebabble digest of specified private or public key             file.     -b bits             Specifies the number of bits in the key to create.  Minimum is             512 bits.  Generally, 1024 bits is considered sufficient.  The             default is 1024 bits.     -C comment             Provides a new comment.     -c      Requests changing the comment in the private and public key             files.  This operation is only supported for RSA1 keys.  The pro-             gram will prompt for the file containing the private keys, for             the passphrase if the key has one, and for the new comment.     -D reader             Download the RSA public key stored in the smartcard in reader.     -e      This option will read a private or public OpenSSH key file and             print the key in a `SECSH Public Key File Format' to stdout.             This option allows exporting keys for use by several commercial             SSH implementations.     -F hostname             Search for the specified hostname in a known_hosts file, listing             any occurrences found.  This option is useful to find hashed host             names or addresses and may also be used in conjunction with the             -H option to print found keys in a hashed format.     -f filename             Specifies the filename of the key file.     -G output_file             Generate candidate primes for DH-GEX.  These primes must be             screened for safety (using the -T option) before use.     -g      Use generic DNS format when printing fingerprint resource records             using the -r command.     -H      Hash a known_hosts file, printing the result to standard output.             This replaces all hostnames and addresses with hashed representa-             tions.  These hashes may be used normally by ssh and sshd, but             they do not reveal identifying information should the file's con-             tents 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.     -i      This option will read an unencrypted private (or public) key file             in SSH2-compatible format and print an OpenSSH compatible private             (or public) key to stdout.  ssh-keygen also reads the `SECSH             Public Key File Format'.  This option allows importing keys from             several commercial SSH implementations.     -l      Show fingerprint of specified public key file.  Private RSA1 keys             are also supported.  For RSA and DSA keys ssh-keygen tries to             find the matching public key file and prints its fingerprint.     -M memory             Specify the amount of memory to use (in megabytes) when generat-             ing candidate moduli for DH-GEX.     -N new_passphrase             Provides the new passphrase.     -P passphrase             Provides the (old) passphrase.     -p      Requests changing the passphrase of a private key file instead of             creating a new private key.  The program will prompt for the file             containing the private key, for the old passphrase, and twice for             the new passphrase.     -q      Silence ssh-keygen.  Used by /etc/rc when creating a new key.     -R hostname             Removes all keys belonging to hostname from a known_hosts file.             This option is useful to delete hashed hosts (see the -H option             above).     -r hostname             Print the SSHFP fingerprint resource record named hostname for             the specified public key file.     -S start             Specify start point (in hex) when generating candidate moduli for             DH-GEX.     -T output_file             Test DH group exchange candidate primes (generated using the -G             option) for safety.     -t type             Specifies the type of key to create.  The possible values are             ``rsa1'' for protocol version 1 and ``rsa'' or ``dsa'' for proto-             col version 2.     -U reader             Upload an existing RSA private key into the smartcard in reader.     -v      Verbose mode.  Causes ssh-keygen to print debugging messages             about its progress.  This is helpful for debugging moduli genera-             tion.  Multiple -v options increase the verbosity.  The maximum             is 3.     -W generator             Specify desired generator when testing candidate moduli for DH-             GEX.     -y      This option will read a private OpenSSH format file and print an             OpenSSH public key to stdout.MODULI GENERATION     ssh-keygen may be used to generate groups for the Diffie-Hellman Group     Exchange (DH-GEX) protocol.  Generating these groups is a two-step pro-     cess: first, candidate primes are generated using a fast, but memory in-     tensive process.  These candidate primes are then tested for suitability     (a CPU-intensive process).     Generation of primes is performed using the -G option.  The desired     length of the primes may be specified by the -b option.  For example:           # ssh-keygen -G moduli-2048.candidates -b 2048     By default, the search for primes begins at a random point in the desired     length range.  This may be overridden using the -S option, which speci-     fies a different start point (in hex).     Once a set of candidates have been generated, they must be tested for     suitability.  This may be performed using the -T option.  In this mode     ssh-keygen will read candidates from standard input (or a file specified     using the -f option).  For example:           # ssh-keygen -T moduli-2048 -f moduli-2048.candidates     By default, each candidate will be subjected to 100 primality tests.     This may be overridden using the -a option.  The DH generator value will     be chosen automatically for the prime under consideration.  If a specific     generator is desired, it may be requested using the -W option.  Valid     generator values are 2, 3, and 5.     Screened DH groups may be installed in /etc/moduli.  It is important that     this file contains moduli of a range of bit lengths and that both ends of     a connection share common moduli.FILES     $HOME/.ssh/identity             Contains the protocol version 1 RSA authentication identity of             the user.  This file should not be readable by anyone but the us-             er.  It is possible to specify a passphrase when generating the             key; that passphrase will be used to encrypt the private part of             this file using 3DES.  This file is not automatically accessed by             ssh-keygen but it is offered as the default file for the private             key.  ssh(1) will read this file when a login attempt is made.     $HOME/.ssh/identity.pub             Contains the protocol version 1 RSA public key for authentica-             tion.  The contents of this file should be added to             $HOME/.ssh/authorized_keys on all machines where the user wishes             to log in using RSA authentication.  There is no need to keep the             contents of this file secret.     $HOME/.ssh/id_dsa             Contains the protocol version 2 DSA authentication identity of             the user.  This file should not be readable by anyone but the us-             er.  It is possible to specify a passphrase when generating the             key; that passphrase will be used to encrypt the private part of             this file using 3DES.  This file is not automatically accessed by             ssh-keygen but it is offered as the default file for the private             key.  ssh(1) will read this file when a login attempt is made.     $HOME/.ssh/id_dsa.pub             Contains the protocol version 2 DSA public key for authentica-             tion.  The contents of this file should be added to             $HOME/.ssh/authorized_keys on all machines where the user wishes             to log in using public key authentication.  There is no need to             keep the contents of this file secret.     $HOME/.ssh/id_rsa             Contains the protocol version 2 RSA authentication identity of             the user.  This file should not be readable by anyone but the us-             er.  It is possible to specify a passphrase when generating the             key; that passphrase will be used to encrypt the private part of             this file using 3DES.  This file is not automatically accessed by             ssh-keygen but it is offered as the default file for the private             key.  ssh(1) will read this file when a login attempt is made.     $HOME/.ssh/id_rsa.pub             Contains the protocol version 2 RSA public key for authentica-             tion.  The contents of this file should be added to             $HOME/.ssh/authorized_keys on all machines where the user wishes             to log in using public key authentication.  There is no need to             keep the contents of this file secret.     /etc/moduli             Contains Diffie-Hellman groups used for DH-GEX.  The file format             is described in moduli(5).SEE ALSO     ssh(1), ssh-add(1), ssh-agent(1), moduli(5), sshd(8)     J. Galbraith and R. Thayer, SECSH Public Key File Format, draft-ietf-     secsh-publickeyfile-01.txt, March 2001, work in progress material.AUTHORS     OpenSSH is a derivative of the original and free ssh 1.2.12 release by     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo     de Raadt and Dug Song removed many bugs, re-added newer features and     created OpenSSH.  Markus Friedl contributed the support for SSH protocol     versions 1.5 and 2.0.OpenBSD 3.6                   September 25, 1999                             5