The ssh-keygen utility generates and manages authentication keys for ssh(1). ssh-keygen defaults to generating an RSA key for use by protocol 2.0.

Each user wishing to use SSH with RSA or DSA authentication normally runs this once to create the authentication key in $HOME/.ssh/identity or $HOME/.ssh/id_dsa. The system administrator may also use this to generate host keys.

Ordinarily, 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 with the ``.pub'' extension appended. The program also asks for a passphrase. The passphrase may be empty to indicate no passphrase (host keys must have empty passphrases), or it may be a string of arbitrary length. Good passphrases are 10-30 characters long and are not simple sentences or otherwise easy to guess. (English prose has only 1-2 bits of entropy per word, and provides very poor passphrases.) 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, you will have to generate a new key and copy the corresponding public key to other machines.

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 ``user@host'' when the key is created, but can be changed using the -c option.

After a key is generated, instructions below detail where to place the keys to activate them.

The following options are supported:

-b bits

Specifies the number of bits in the key to create. The minimum number is 512 bits. Generally, 1024 bits is considered sufficient. Key sizes above that no longer improve security but make things slower. The default is 1024 bits.

-c

Requests changing the comment in the private and public key files. The program will prompt for the file containing the private keys, for the passphrase if the key has one, and for the new comment.

-C comment

Provides the new comment.

-f

Specifies the filename of the key file.

-l

Shows the fingerprint of the specified private or public key file.

-N new_passphrase

Provides the new 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 will prompt twice for the new passphrase.

-P passphrase

Provides the (old) passphrase.

-q

Silences ssh-keygen. Used by /etc/rc when creating a new key.

-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.

-t type

Specifies the algorithm used for the key, where type is one of rsa, dsa, and rsa1. Type rsa1 is used only for the SSHv1 protocol

-x

Reads a private OpenSSH DSA format file and prints an SSH2-compatible public key to stdout.

-X

Reads an unencrypted SSH2-compatible private (or public) key file and prints an OpenSSH compatible private (or public) key to stdout.

-y

Reads a private OpenSSH DSA format file and prints an OpenSSH DSA public key to stdout.

The following exit values are returned:

0

Successful completion.

1

An error occurred.

$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 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. sshd(1M) will read this file when a login attempt is made.

$HOME/.ssh/identity.pub

Contains the public key for authentication. The contents of this file should be added to $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.

$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 ssh-keygen but it is offered as the default file for the private key. sshd(1M) will read this file when a login attempt is made.

$HOME/.ssh/id_dsa.pub

Contains the public key for authentication. The contents of this file should be added to $HOME/.ssh/authorized_keys on all machines where you wish to log in using DSA authentication. There is no need to keep the contents of this file secret.

See attributes(5) for descriptions of the following attributes:

ssh(1), ssh-add(1), ssh-agent(1), sshd(1M), attributes(5)

To view license terms, attribution, and copyright for OpenSSH, the default path is /var/sadm/pkg/SUNWsshdr/install/copyright. If the Solaris operating environment has been installed anywhere other than the default, modify the given path to access the file at the installed location.