I think what you're really looking for here is to be able to create a secure connection between your site and the user's browser. I believe what you need to do this is a ssl certificate. I haven't done this before (though I am somewhat interested, so I'm glad you asked...).
I think its a three step process:
1) Generate an ssl request:
https://cp.freehostia.com/tutorials/sup ... st_csr.htm
2) Submit your request to a certificate authority (??? not sure how)
3) upload your certificate to your website:
https://cp.freehostia.com/tutorials/sup ... ficate.htm
This will allow encrypted communications between user's browsers and your site.
Hope that helps, let us know if you work this out. Also you might want to open a ticket with freehostia to have them help you more.