-.\" $OpenBSD: ssh-keygen.1,v 1.66 2005/03/01 18:15:56 jmc Exp $
+.\" $OpenBSD: ssh-keygen.1,v 1.79 2008/07/24 23:55:30 sthen Exp $
.\"
.\" -*- nroff -*-
.\"
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
-.Dd September 25, 1999
+.Dd $Mdocdate: July 24 2008 $
.Dt SSH-KEYGEN 1
.Os
.Sh NAME
.Nm ssh-keygen
.Fl F Ar hostname
.Op Fl f Ar known_hosts_file
+.Op Fl l
.Nm ssh-keygen
.Fl H
.Op Fl f Ar known_hosts_file
The type of key to be generated is specified with the
.Fl t
option.
+If invoked without any arguments,
+.Nm
+will generate an RSA key for use in SSH protocol 2 connections.
.Pp
.Nm
is also used to generate groups for use in Diffie-Hellman group
Normally each user wishing to use SSH
with RSA or DSA authentication runs this once to create the authentication
key in
-.Pa $HOME/.ssh/identity ,
-.Pa $HOME/.ssh/id_dsa
+.Pa ~/.ssh/identity ,
+.Pa ~/.ssh/id_dsa
or
-.Pa $HOME/.ssh/id_rsa .
+.Pa ~/.ssh/id_rsa .
Additionally, the system administrator may use this to generate host keys,
as seen in
.Pa /etc/rc .
Show the bubblebabble digest of specified private or public key file.
.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.
-The default is 1024 bits.
+For RSA keys, the minimum size is 768 bits and the default is 2048 bits.
+Generally, 2048 bits is considered sufficient.
+DSA keys must be exactly 1024 bits as specified by FIPS 186-2.
.It Fl C Ar comment
Provides a new comment.
.It Fl c
.Ar reader .
.It Fl e
This option will read a private or public OpenSSH key file and
-print the key in a
-.Sq SECSH Public Key File Format
+print the key in
+RFC 4716 SSH Public Key File Format
to stdout.
This option allows exporting keys for use by several commercial
SSH implementations.
.It Fl H
Hash a
.Pa known_hosts
-file, printing the result to standard output.
-This replaces all hostnames and addresses with hashed representations.
+file.
+This replaces all hostnames and addresses with hashed representations
+within the specified file; the original content is moved to a file with
+a .old suffix.
These hashes may be used normally by
.Nm ssh
and
(or public) key to stdout.
.Nm
also reads the
-.Sq SECSH Public Key File Format .
+RFC 4716 SSH Public Key File Format.
This option allows importing keys from several commercial
SSH implementations.
.It Fl l
For RSA and DSA keys
.Nm
tries to find the matching public key file and prints its fingerprint.
+If combined with
+.Fl v ,
+an ASCII art representation of the key is supplied with the fingerprint.
.It Fl M Ar memory
Specify the amount of memory to use (in megabytes) when generating
candidate moduli for DH-GEX.
that both ends of a connection share common moduli.
.Sh FILES
.Bl -tag -width Ds
-.It Pa $HOME/.ssh/identity
+.It Pa ~/.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
but it is offered as the default file for the private key.
.Xr ssh 1
will read this file when a login attempt is made.
-.It Pa $HOME/.ssh/identity.pub
+.It Pa ~/.ssh/identity.pub
Contains the protocol version 1 RSA public key for authentication.
The contents of this file should be added to
-.Pa $HOME/.ssh/authorized_keys
+.Pa ~/.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.
-.It Pa $HOME/.ssh/id_dsa
+.It Pa ~/.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
but it is offered as the default file for the private key.
.Xr ssh 1
will read this file when a login attempt is made.
-.It Pa $HOME/.ssh/id_dsa.pub
+.It Pa ~/.ssh/id_dsa.pub
Contains the protocol version 2 DSA public key for authentication.
The contents of this file should be added to
-.Pa $HOME/.ssh/authorized_keys
+.Pa ~/.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.
-.It Pa $HOME/.ssh/id_rsa
+.It Pa ~/.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
but it is offered as the default file for the private key.
.Xr ssh 1
will read this file when a login attempt is made.
-.It Pa $HOME/.ssh/id_rsa.pub
+.It Pa ~/.ssh/id_rsa.pub
Contains the protocol version 2 RSA public key for authentication.
The contents of this file should be added to
-.Pa $HOME/.ssh/authorized_keys
+.Pa ~/.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.
.Xr moduli 5 ,
.Xr sshd 8
.Rs
-.%A J. Galbraith
-.%A R. Thayer
-.%T "SECSH Public Key File Format"
-.%N draft-ietf-secsh-publickeyfile-01.txt
-.%D March 2001
-.%O work in progress material
+.%R RFC 4716
+.%T "The Secure Shell (SSH) Public Key File Format"
+.%D 2006
.Re
.Sh AUTHORS
OpenSSH is a derivative of the original and free