User Commands ssh-keygen(1)
NAME
ssh-keygen - authentication key generation
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 -F hostname [-f known_hosts_file]
ssh-keygen -H [-f known_hosts_file]
ssh-keygen -R hostname [-f known_hosts_file]
DESCRIPTION
The ssh-keygen utility 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 begenerated is specified with the -t option.
Normally, each user wishing to use SSH with RSA or DSA authentication runs this once to create the authenticationkey in $HOME/.ssh/identity, $HOME/.ssh/id_dsa, or
$HOME/.ssh/id_rsa. The system administrator can also use
this to generate host keys..SunOS 5.11 Last change: 29 Mar 2010 1
User Commands ssh-keygen(1)
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 can be empty to indicate no passphrase (host keys must have empty passphrases), or it can be a string ofarbitrary length. Good passphrases are 10-30 characters
long, are not simple sentences or otherwise easy to guess, and contain a mix of uppercase and lowercase letters,numbers, and non-alphanumeric characters. (English prose has
only 1-2 bits of entropy per word and provides very poor
passphrases.) If a passphrase is set, it must be at least 4 characters long.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 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'' whenthe 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. OPTIONS The following options are supported:-b bits Specifies the number of bits in the key
to create. The minimum number is 512bits. Generally, 2048 bits is con-
sidered sufficient. Key sizes above that no longer improve security but make things slower. The default is 2048 bits.-B Shows the bubblebabble digest of the
specified private or public key file.-c Requests changing the comment in the
private and public key files. The pro-
gram prompts for the file containingSunOS 5.11 Last change: 29 Mar 2010 2
User Commands ssh-keygen(1)
the private keys, for the passphrase ifthe key has one, and for the new com-
ment. This option only applies to rsa1 (SSHv1) keys.-C comment Provides the new comment.
-e This option reads a private or public
OpenSSH key file and prints the key in a "SECSH" Public Key File Format to stdout. This option allows exporting keys for use by several other SSH implementations.-f Specifies the filename of the key file.
-F Search for the specified hostname in a
known_hosts file, listing any
occurrences found. This option is use-
ful to find hashed host names oraddresses and can also be used in con-
junction with the -H option to print
found keys in a hashed format.-H Hash a known_hosts file. This replaces
all host names 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 ssh and sshd, but they do not reveal identifying information should the file's contents be disclosed. This option does not modify existing hashed host names and is therefore safe to useon files that mix hashed and non-hashed
names.-i This option reads an unencrypted
private (or public) key file in SSH2-
compatible format and prints an OpenSSH compatible private (or public) key tostdout. ssh-keygen also reads the
"SECSH" Public Key File Format. ThisSunOS 5.11 Last change: 29 Mar 2010 3
User Commands ssh-keygen(1)
option allows importing keys from several other SSH implementations.-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 prompts for the file containing the private key, for the old passphrase, and prompts twice for the new passphrase.-P passphrase Provides the (old) passphrase.
-q Silences ssh-keygen.
-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.-R hostname Removes all keys belonging to hostname
from a known_hosts file. This option is
useful to delete hashed hosts. See -H.
-x Obsolete. Replaced by the -e option.
-X Obsolete. Replaced by the -i option.
-y This option reads a private OpenSSH
format file and prints an OpenSSH pub-
lic key to stdout. EXIT STATUS The following exit values are returned: 0 Successful completion.SunOS 5.11 Last change: 29 Mar 2010 4
User Commands ssh-keygen(1)
1 An error occurred. FILES$HOME/.ssh/identity This file contains the RSA
private key for the SSHv1 proto-
col. This file should not be readable by anyone but the user. It is possible to specify a passphrase when generating the key; that passphrase is used to encrypt the private part of this file using 3DES. This file is notautomatically accessed by ssh-
keygen, but it is offered as the default file for the private key. sshd(1M) reads this file when a login attempt is made.$HOME/.ssh/identity.pub This file contains the RSA public
key for the SSHv1 protocol. The contents of this file should be added to$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 These files contain, respec-
$HOME/.ssh/id_rsa tively, the DSA or RSA private
key for the SSHv2 protocol. These files should not be readable byanyone but the user. It is possi-
ble to specify a passphrase when generating the key; that passphrase is used to encrypt the private part of the file using 3DES. Neither of these files isautomatically accessed by ssh-
keygen but is offered as the default file for the private key. sshd(1M) reads this file when a login attempt is made.$HOME/.ssh/id_dsa.pub These files contain, respec-
$HOME/.ssh/id_rsa.pub tively, the DSA or RSA public key
for the SSHv2 protocol. The con-
tents of these files should beSunOS 5.11 Last change: 29 Mar 2010 5
User Commands ssh-keygen(1)
added, respectively, to$HOME/.ssh/authorized_keys on all
machines where you wish to log in using DSA or RSA authentication.There is no need to keep the con-
tents of these files secret.ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | network/ssh/ssh-key |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
SEE ALSO
ssh(1), ssh-add(1), ssh-agent(1), sshd(1M), attributes(5)
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