.Nd authentication key generation
.Sh SYNOPSIS
.Nm ssh-keygen
-.Op Fl q
+.Op Fl dq
.Op Fl b Ar bits
.Op Fl N Ar new_passphrase
.Op Fl C Ar comment
.Op Fl N Ar new_passphrase
.Op Fl f Ar keyfile
.Nm ssh-keygen
+.Fl x
+.Op Fl f Ar keyfile
+.Nm ssh-keygen
+.Fl X
+.Op Fl f Ar keyfile
+.Nm ssh-keygen
+.Fl y
+.Op Fl f Ar keyfile
+.Nm ssh-keygen
.Fl c
.Op Fl P Ar passphrase
.Op Fl C Ar comment
.Nm ssh-keygen
.Fl l
.Op Fl f Ar keyfile
-.Sh DESCRIPTION
+.Nm ssh-keygen
+.Fl R
+.Sh DESCRIPTION
.Nm
-generates and manages authentication keys for
+generates and manages authentication keys for
.Xr ssh 1 .
+.Nm
+defaults to generating an RSA key for use by protocols 1.3 and 1.5;
+specifying the
+.Fl d
+flag will create a DSA key instead for use by protocol 2.0.
+.Pp
Normally each user wishing to use SSH
-with RSA authentication runs this once to create the authentication
+with RSA or DSA authentication runs this once to create the authentication
key in
-.Pa $HOME/.ssh/identity .
-Additionally, the system administrator may use this to generate host keys.
+.Pa $HOME/.ssh/identity
+or
+.Pa $HOME/.ssh/id_dsa .
+Additionally, the system administrator may use this to generate host keys,
+as seen in
+.Pa /etc/rc .
.Pp
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
+to store the private key.
+The public key is stored in a file with the same name but
.Dq .pub
-appended. The program also asks for a
-passphrase. The passphrase may be empty to indicate no passphrase
+appended.
+The program also asks for a passphrase.
+The passphrase may be empty to indicate no passphrase
(host keys must have empty passphrase), or it may be a string of
-arbitrary length. Good passphrases are 10-30 characters long and are
+arbitrary length.
+Good passphrases are 10-30 characters long and are
not simple sentences or otherwise easily guessable (English
prose has only 1-2 bits of entropy per word, and provides very bad
-passphrases). The passphrase can be changed later by using the
+passphrases).
+The passphrase can be changed later by using the
.Fl p
option.
.Pp
-There is no way to recover a lost passphrase. If the passphrase is
+There is no way to recover a lost passphrase.
+If the passphrase is
lost or forgotten, you will have to generate a new key and copy the
corresponding public key to other machines.
.Pp
-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
+For RSA, 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
.Dq user@host
when the key is created, but can be changed using the
.Fl c
option.
.Pp
+After a key is generated, instructions below detail where the keys
+should be placed to be activated.
+.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b Ar 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 security but make things slower. The
-default is 1024 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 security but make things slower.
+The default is 1024 bits.
.It Fl c
Requests changing the comment in the private and public key files.
The program will prompt for the file containing the private keys, for
Show fingerprint of specified private or public key file.
.It Fl p
Requests changing the passphrase of a private key file instead of
-creating a new private key. The program will prompt for the file
+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.
.It Fl q
Provides the new passphrase.
.It Fl P Ar passphrase
Provides the (old) passphrase.
+.It Fl R
+If RSA support is functional, immediately exits with code 0. If RSA
+support is not functional, exits with code 1. This flag will be
+removed once the RSA patent expires.
+.It Fl x
+This option will read a private
+OpenSSH DSA format file and print a SSH2-compatible public key to stdout.
+.It Fl X
+This option will read a
+SSH2-compatible public key file and print an OpenSSH DSA compatible public key to stdout.
+.It Fl y
+This option will read a private
+OpenSSH DSA format file and print an OpenSSH DSA public key to stdout.
.El
.Sh FILES
.Bl -tag -width Ds
.It Pa $HOME/.ssh/identity
-Contains the RSA authentication identity of the user. This file
-should not be readable by anyone but the user. It is possible to
+Contains the 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 private part of this file using 3DES. This file
-is not automatically accessed by
+used to encrypt the private part of this file using 3DES.
+This file is not automatically accessed by
.Nm
but it is offered as the default file for the private key.
+.Xr sshd 8
+will read this file when a login attempt is made.
.It Pa $HOME/.ssh/identity.pub
-Contains the public key for authentication. The contents of this file
-should be added to
+Contains the public key for authentication.
+The contents of this file should be added to
.Pa $HOME/.ssh/authorized_keys
on all machines
-where you wish to log in using RSA authentication. There is no
-need to keep the contents of this file secret.
+where you wish to log in using RSA authentication.
+There is no need to keep the contents of this file secret.
+.It Pa $HOME/.ssh/id_dsa
+Contains the 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 private part of this file using 3DES.
+This file is not automatically accessed by
+.Nm
+but it is offered as the default file for the private key.
+.Xr sshd 8
+will read this file when a login attempt is made.
+.It Pa $HOME/.ssh/id_dsa.pub
+Contains the public key for authentication.
+The contents of this file should be added to
+.Pa $HOME/.ssh/authorized_keys2
+on all machines
+where you wish to log in using DSA authentication.
+There is no need to keep the contents of this file secret.
.Sh AUTHOR
Tatu Ylonen <ylo@cs.hut.fi>
.Pp
OpenSSH
is a derivative of the original (free) ssh 1.2.12 release, but with bugs
-removed and newer features re-added. Rapidly after the 1.2.12 release,
-newer versions bore successively more restrictive licenses. This version
-of OpenSSH
+removed and newer features re-added.
+Rapidly after the 1.2.12 release,
+newer versions bore successively more restrictive licenses.
+This version of OpenSSH
.Bl -bullet
.It
-has all components of a restrictive nature (i.e., patents, see
-.Xr ssl 8 )
+has all components of a restrictive nature (i.e., patents)
directly removed from the source code; any licensed or patented components
are chosen from
external libraries.
.It
has been updated to support ssh protocol 1.5.
.It
-contains added support for
+contains added support for
.Xr kerberos 8
authentication and ticket passing.
.It
supports one-time password authentication with
.Xr skey 1 .
.El
-.Pp
-The libraries described in
-.Xr ssl 8
-are required for proper operation.
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-agent 1 ,
.Xr sshd 8 ,
-.Xr ssl 8
andersk / openssh.git / blobdiff