secure file copying

hi all, is there a way to copy/move a file (backup) secure over the network ? at this time we use ssh with a useraccount which has no password. sounds unsecure eh ? :) i know that it is possible for everyone on the machine "a" to connect to machine "b" when he knows 1) the non-password useracc and 2) the ip where the ssh-key with no-password is stored. what happens if the ssh-key with the non-passwd is stolen or may be used by an attacker to get more accounts or root ? i don´t know how this could help him, but i think its not the best way to transfer the files with this method. any ideas ? thx Marco A. --