With a paypal pro there is a NVP API interface (name value pair) that you post from an https server, I am trying to send address details for a subscription from flash.

Here is an old version of the NVP docs, not sure if current pdf is publicly available and figured you would not want to download http://www.scribd.com/doc/6035142/PP-NVPAPI-Developer-Guide

Anyway I am worried about hard coding API password etc in a swf, so was thinking since they want the address fields in the swf that maybe external interface would be more secure that way atleast the API password could stay in hidden form fields in the https html.

I don't really know much about https or flash security issues for this area I am only working on the flash part, and thought maybe someone may have some knowledge. As I said maybe this would be better as html but that is not what is on the wireframe. My other worry is that if the swf is not cached which might be good for security but not so for download times ( there is some other stuff like fb connection to flash ( I guess it will still work once the page is https? and streamed or progressive video )).

Anyway https/paypal/flash security experts please comment ( code welcome )

I mean send from the html page but use External Interface to send the data to the https html from flash.

we moved the from to html it just seemed a better option.