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RedHat 9 (Linux i386) - man page for ssh-keygen (redhat section 1)

SSH-KEYGEN(1)			   BSD General Commands Manual			    SSH-KEYGEN(1)

NAME
     ssh-keygen -- authentication key generation, management and conversion

SYNOPSIS
     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 -U reader [-f input_keyfile]

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 proto-
     col version 2. The type of key to be generated is specified with the -t option.

     Normally each user wishing to use SSH with RSA or DSA authentication runs this once to cre-
     ate the authentication key in $HOME/.ssh/identity, $HOME/.ssh/id_dsa or $HOME/.ssh/id_rsa.
     Additionally, the system administrator may use this to generate host keys, as seen in
     /etc/rc.

     Normally this program generates the key and asks for a file in which to store the private
     key.  The public key is stored in a file with the same name but ``.pub'' appended.  The pro-
     gram also asks for a passphrase.  The passphrase may be empty to indicate no passphrase
     (host keys must have an empty passphrase), or it may be a string of arbitrary length.  A
     passphrase is similar to a password, except it can be a phrase with a series of words, punc-
     tuation, numbers, whitespace, or any string of characters you want.  Good passphrases are
     10-30 characters long, are not simple sentences or otherwise easily guessable (English prose
     has only 1-2 bits of entropy per character, and provides very bad passphrases), and contain
     a mix of upper and lowercase letters, numbers, and non-alphanumeric characters.  The
     passphrase can be changed later by using the -p option.

     There is no way to recover a lost passphrase.  If the passphrase is lost or forgotten, a new
     key must be generated and 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 initialized 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:

     -b bits
	     Specifies the number of bits in the key to create.  Minimum is 512 bits.  Generally
	     1024 bits is considered sufficient, and key sizes above that no longer improve secu-
	     rity but make things slower.  The default is 1024 bits.

     -c      Requests changing the comment in the private and public key files.  This operation
	     is only supported for RSA1 keys.  The program will prompt for the file containing
	     the private keys, for the passphrase if the key has one, and for the new comment.

     -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 filename
	     Specifies the filename of the key file.

     -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 sup-
	     ported.  For RSA and DSA keys ssh-keygen tries to find the matching public key file
	     and prints its fingerprint.

     -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.

     -y      This option will read a private OpenSSH format file and print an OpenSSH public key
	     to stdout.

     -t type
	     Specifies the type of the key to create.  The possible values are ``rsa1'' for pro-
	     tocol version 1 and ``rsa'' or ``dsa'' for protocol version 2.

     -B      Show the bubblebabble digest of specified private or public key file.

     -C comment
	     Provides the new comment.

     -D reader
	     Download the RSA public key stored in the smartcard in reader.

     -N new_passphrase
	     Provides the new passphrase.

     -P passphrase
	     Provides the (old) passphrase.

     -U reader
	     Upload an existing RSA private key into the smartcard in reader.

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 user.  It is possible to specify a
	     passphrase when generating the key; that passphrase will be used to encrypt the pri-
	     vate 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 authentication.  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 con-
	     tents 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 user.  It is possible to specify a
	     passphrase when generating the key; that passphrase will be used to encrypt the pri-
	     vate 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 authentication.  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 user.  It is possible to specify a
	     passphrase when generating the key; that passphrase will be used to encrypt the pri-
	     vate 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 authentication.  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.

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.

SEE ALSO
     ssh(1), ssh-add(1), ssh-agent(1), sshd(8)

     J. Galbraith and R. Thayer, SECSH Public Key File Format, draft-ietf-secsh-
     publickeyfile-01.txt, March 2001, work in progress material.

BSD					September 25, 1999				      BSD


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