ftp:ssl-allow (boolean)
              if true, try to negotiate SSL connection with ftp server for non-anonymous access. Default is true. This and other ssl settings are  only
              available if lftp was compiled with an ssl/tls library.

       ftp:ssl-data-use-keys (boolean)
              if  true,  lftp  loads ssl:key-file for protected data connection too. When false, it does not, and the server can match data and control
              connections by session ID.  Default is true.

       ftp:ssl-force (boolean)
              if true, refuse to send password in clear when server does not support SSL.  Default is false.

       ftp:ssl-protect-data (boolean)
              if true, request ssl connection for data transfers. This is cpu-intensive but provides privacy. Default is false.

       ftp:ssl-protect-fxp (boolean)
              if true, request ssl connection for data transfer between two ftp servers in FXP mode. CPSV or SSCN command will be used in that case. If
              ssl  connection  fails  for  some reason, lftp would try unprotected FXP transfer unless ftp:ssl-force is set for any of the two servers.
              Default is false.

       ftp:ssl-protect-list (boolean)
              if true, request ssl connection for file list transfers. Default is true.

       ftp:ssl-use-ccc (boolean)
              if true, lftp would issue CCC command after logon, thus disable ssl protection layer on control connection.