How can I securely accept form data in a jsonp request within my mvc app?

I have a need to accept form data from other web sites to a central MVC application. The fo开发者_如何学Pythonrm data is just strings of name value pairs and they vary from site-to-site. I plan to concatenate all values and delimit them with a special character. Up to this point, I think I can do this with a JSONP type request using AJAX. What I'm concerned with is authenticating the incoming 'post'.

So is this possible? Is this the worst way to do it? (I've been known to pick 'em!)