On some ftp servers you can require SSL encryption. However that's only for the login. As far as your friends go, it's relatively easy to get them a "static" ip address. I haven't tested this theory yet, but I think it will work. Go to dyndns.org and sign up for their dns server. They will give you a domain name like bob.isa-geek.com. Next get a dns updater, the site will give you options or you can go to download.com and get one. It essentially gives your machine the same IP address but the domain name is mapped to the dynamic ip. Pretty sure that you can give the dns access as opposed to an IP. Just a theory, but I think it will work.