[07] DOES SDF SUPPORT SSH AUTHORIZED_KEYS FOR AUTHENTICATION?

     Yes, to set this up on a Unix system, please follow the steps below.
     Windows users might want to read about PuTTY Key Generator instead.

     1. Run 'ssh-keygen -t rsa' on your host (the machine you plan to login
        from). This will create a public key "id_rsa.pub" and private key
        "id_rsa" under $HOME/.ssh . You have the option of protecting your
        private key with a password, in the event that the $HOME directory
        on your host is ever breached.
        (Note: other types of keys, like DSA and ED25519, are not known to
        work at present.)

     2. Log in to SDF, and put the contents of your newly-created *.pub key
        in the file $HOME/.ssh/authorized_keys (create it if it does not
        already exist).

     3. Set the appropriate permissions on $HOME/.ssh
        (Run 'chmod -R 700 $HOME/.ssh' so that group and world on SDF
        cannot read the directory).

     4. Return to the machine you plan to login from, and create the file
        $HOME/.ssh/config containing the following stanza. Replace ${LOGNAME}
        with your SDF username.
        Host tty.sdf.org
            Hostname tty.sdf.org
            PreferredAuthentications publickey,keyboard-interactive,password
            IdentitiesOnly yes
            IdentityFile ~/.ssh/id_rsa
            User ${LOGNAME}

     You should now be able to login via ssh without being prompted for a
     password (unless you password-protected your private key, in which case
     you will be prompted for the password by your ssh client).