pubkey.but

putty

To alter the key comment, just type your comment text into the
\q{Key comment} box before saving the private key. If you want to
change the comment later, you can load the private key back into
PuTTYgen, change the comment, and save it again.

\S{puttygen-passphrase} Setting a \i{passphrase} for your key

\cfg{winhelp-topic}{puttygen.passphrase}

The \q{Key passphrase} and \q{Confirm passphrase} boxes allow you to
choose a passphrase for your key. The passphrase will be used to
\i{encrypt} the key on disk, so you will not be able to use the key
without first entering the passphrase.

When you save the key, PuTTYgen will check that the \q{Key passphrase}
and \q{Confirm passphrase} boxes both contain exactly the same
passphrase, and will refuse to save the key otherwise.

If you leave the passphrase fields blank, the key will be saved
unencrypted. You should \e{not} do this without good reason; if you
do, your private key file on disk will be all an attacker needs to
gain access to any machine configured to accept that key. If you
want to be able to \i{passwordless login}log in without having to
type a passphrase every time, you should consider using Pageant
(\k{pageant}) so that your decrypted key is only held in memory
rather than on disk.

Under special circumstances you may genuinely \e{need} to use a key
with no passphrase; for example, if you need to run an automated
batch script that needs to make an SSH connection, you can't be
there to type the passphrase. In this case we recommend you generate
a special key for each specific batch script (or whatever) that
needs one, and on the server side you should arrange that each key
is \e{restricted} so that it can only be used for that specific
purpose. The documentation for your SSH server should explain how to
do this (it will probably vary between servers).

Choosing a good passphrase is difficult. Just as you shouldn't use a
dictionary word as a password because it's easy for an attacker to
run through a whole dictionary, you should not use a song lyric,
quotation or other well-known sentence as a passphrase. \i{DiceWare}
(\W{http://www.diceware.com/}\cw{www.diceware.com}) recommends using
at least five words each generated randomly by rolling five dice,
which gives over 2^64 possible passphrases and is probably not a bad
scheme. If you want your passphrase to make grammatical sense, this
cuts down the possibilities a lot and you should use a longer one as
a result.

\e{Do not forget your passphrase}. There is no way to recover it.

\S{puttygen-savepriv} Saving your private key to a disk file

\cfg{winhelp-topic}{puttygen.savepriv}

Once you have generated a key, set a comment field and set a
passphrase, you are ready to save your private key to disk.

Press the \q{Save private key} button. PuTTYgen will put up a dialog
box asking you where to save the file. Select a directory, type in a
file name, and press \q{Save}.

This file is in PuTTY's native format (\c{*.\i{PPK}}); it is the one you
will need to tell PuTTY to use for authentication (see
\k{config-ssh-privkey}) or tell Pageant to load (see
\k{pageant-mainwin-addkey}).

\S{puttygen-savepub} Saving your public key to a disk file

\cfg{winhelp-topic}{puttygen.savepub}

RFC 4716 specifies a \I{SSH-2 public key format}standard format for
storing SSH-2 public keys on disk. Some SSH servers (such as
\i\cw{ssh.com}'s) require a public key in this format in order to accept
authentication with the corresponding private key. (Others, such as
OpenSSH, use a different format; see \k{puttygen-pastekey}.)

To save your public key in the SSH-2 standard format, press the
\q{Save public key} button in PuTTYgen. PuTTYgen will put up a
dialog box asking you where to save the file. Select a directory,
type in a file name, and press \q{Save}.

You will then probably want to copy the public key file to your SSH
server machine. See \k{pubkey-gettingready} for general instructions
on configuring public-key authentication once you have generated a
key.

If you use this option with an SSH-1 key, the file PuTTYgen saves
will contain exactly the same text that appears in the \q{Public key
for pasting} box. This is the only existing standard for SSH-1
public keys.

\S{puttygen-pastekey} \q{Public key for pasting into \i{authorized_keys
file}}

\cfg{winhelp-topic}{puttygen.pastekey}

All SSH-1 servers require your public key to be given to it in a
one-line format before it will accept authentication with your
private key. The \i{OpenSSH} server also requires this for SSH-2.

The \q{Public key for pasting into authorized_keys file} gives the
public-key data in the correct one-line format. Typically you will
want to select the entire contents of the box using the mouse, press
Ctrl+C to copy it to the clipboard, and then paste the data into a
PuTTY session which is already connected to the server.

See \k{pubkey-gettingready} for general instructions on configuring
public-key authentication once you have generated a key.

\S{puttygen-load} Reloading a private key

\cfg{winhelp-topic}{puttygen.load}

PuTTYgen allows you to load an existing private key file into
memory. If you do this, you can then change the passphrase and
comment before saving it again; you can also make extra copies of
the public key.

To load an existing key, press the \q{Load} button. PuTTYgen will
put up a dialog box where you can browse around the file system and
find your key file. Once you select the file, PuTTYgen will ask you
for a passphrase (if necessary) and will then display the key
details in the same way as if it had just generated the key.

If you use the Load command to load a foreign key format, it will
work, but you will see a message box warning you that the key you
have loaded is not a PuTTY native key. See \k{puttygen-conversions}
for information about importing foreign key formats.

\S{puttygen-conversions} Dealing with private keys in other formats

\cfg{winhelp-topic}{puttygen.conversions}

Most SSH-1 clients use a standard format for storing private keys on
disk. PuTTY uses this format as well; so if you have generated an
SSH-1 private key using OpenSSH or \cw{ssh.com}'s client, you can use
it with PuTTY, and vice versa.

However, SSH-2 private keys have no standard format. \I{OpenSSH private
key format}OpenSSH and \I{ssh.com private key format}\cw{ssh.com} have
different formats, and PuTTY's is different again.
So a key generated with one client cannot immediately be used with
another.

Using the \I{importing keys}\q{Import} command from the \q{Conversions}
menu, PuTTYgen can load SSH-2 private keys in OpenSSH's format and
\cw{ssh.com}'s format. Once you have loaded one of these key types, you
can then save it back out as a PuTTY-format key (\c{*.\i{PPK}}) so that
you can use it with the PuTTY suite. The passphrase will be unchanged by this
process (unless you deliberately change it). You may want to change
the key comment before you save the key, since OpenSSH's SSH-2 key
format contains no space for a comment and \cw{ssh.com}'s default
comment format is long and verbose.

PuTTYgen can also \i{export private keys} in OpenSSH format and in
\cw{ssh.com} format. To do so, select one of the \q{Export} options
from the \q{Conversions} menu. Exporting a key works exactly like
saving it (see \k{puttygen-savepriv}) - you need to have typed your
passphrase in beforehand, and you will be warned if you are about to
save a key without a passphrase.

Note that since only SSH-2 keys come in different formats, the export
options are not available if you have generated an SSH-1 key.

\H{pubkey-gettingready} Getting ready for public key authentication

Connect to your SSH server using PuTTY with the SSH protocol. When the
connection succeeds you will be prompted for your user name and
password to login. Once logged in, you must configure the server to
accept your public key for authentication:

\b If your server is using the SSH-1 protocol, you should change
into the \i\c{.ssh} directory and open the file \i\c{authorized_keys}
with your favourite editor. (You may have to create this file if
this is the first key you have put in it). Then switch to the
PuTTYgen window, select all of the text in the \q{Public key for
pasting into authorized_keys file} box (see \k{puttygen-pastekey}),
and copy it to the clipboard (\c{Ctrl+C}). Then, switch back to the
PuTTY window and insert the data into the open file, making sure it
ends up all on one line. Save the file.

\b If your server is \i{OpenSSH} and is using the SSH-2 protocol, you
should follow the same instructions, except that in earlier versions
of OpenSSH 2 the file might be called \c{authorized_keys2}. (In
modern versions the same \c{authorized_keys} file is used for both
SSH-1 and SSH-2 keys.)

\b If your server is \i\cw{ssh.com}'s product and is using SSH-2, you
need to save a \e{public} key file from PuTTYgen (see
\k{puttygen-savepub}), and copy that into the \i\c{.ssh2} directory on
the server. Then you should go into that \c{.ssh2} directory, and edit
(or create) a file called \c{authorization}. In this file you should
put a line like \c{Key mykey.pub}, with \c{mykey.pub} replaced by the
name of your key file.

\b For other SSH server software, you should refer to the manual for
that server.

You may also need to ensure that your home directory, your \c{.ssh}
directory, and any other files involved (such as
\c{authorized_keys}, \c{authorized_keys2} or \c{authorization}) are
not group-writable or world-writable. You can typically do this by
using a command such as

\c chmod go-w $HOME $HOME/.ssh $HOME/.ssh/authorized_keys

Your server should now be configured to accept authentication using
your private key. Now you need to configure PuTTY to \e{attempt}
authentication using your private key. You can do this in any of
three ways:

\b Select the private key in PuTTY's configuration. See
\k{config-ssh-privkey} for details.

\b Specify the key file on the command line with the \c{-i} option.
See \k{using-cmdline-identity} for details.

\b Load the private key into Pageant (see \k{pageant}). In this case
PuTTY will automatically try to use it for authentication if it can.