15. Using PuTTY with SSH2 Keys to Access (Open)SSH Servers

   1. Generate a new key pair using the PuTTYgen program on your PC:

      . Select SSH2 DSA, 1024 bits in the key and click on Generate
      . Follow the instructions to wiggle your mouse and wait .
      . Make sure that you type a Key passphrase into the box and the same
        pass phrase into the Confirm passphrase box.
      . Save the generated key by clicking on Save private key choosing the
        name of the computer, eg. bohrg, which you will wish to access
        using this key.  A file eg. bohrg.ppk will be saved to your default
        directory.

   2. Whilst still using PuTTYgen:

      . Copy the public key text (printed in the large box) into a file for
        the remote server (the computer which you will want to access).
        The file containing your keys on the remote server will need to be
        called .ssh/authorized_keys2 (or .ssh/authorized_keys on older
        computers like psiphi).
      . This is most easily accomplished by using copy (CTRL-c) and then
        paste into a file on your PC.   Very important note: each public
        key must be on one single continuous line:  The line will start
        with ssh-dss, then a space, then a long text string ending with
        == dsa-key-.... with no intervening new-line characters.
      . You must then have this file transferred onto the server if you are
        unable to ftp or sftp it there yourself, and the contents of the
        current authorized_keys file, if there is one, must be merged with
        it.  This final step is analogous to transferring a key file
        (.ssh/id_dsa.pub) which was generated using ssh-keygen on unix or
        cygwin (see http://mctalby.mc.man.ac.uk/~mc/_ssh/ssh.2.html).

   3. To log into the remote server using PuTTY and keys:

         . Select the SHH Category and select Preferred SSH protocol
           version 2 only
         . Select the SSH-Auth category and click on Browse and select your
           private key file eg. bohrg.ppk.
         . Return to Session category and use PuTTY as normal, entering the
           hostname of the server and finally clicking on Open.
         . An alternative to specifying the private key file using the SSH-
           Auth-Browse method above is to double click on the bohrg.ppk
           file icon, enter the passphrase and let PuTTY use the Pageant
           program to deal with your keys automatically in the background .