I have a project with the following aspects:
Frontend web application made in PHP, jQuery (Ajax) with a local database for aspects like end users authetication and configuration of the frontend web application.
Backend REST Web Services (running in other domain and machine than frontend application), invoked by the frontend using jQuery and JSONP technique.
I need make that communication in a secure way and I don't know how. I hope someone can help me. I'll be very very grateful.