How to secure SWFs in same domain name?

I want to secure and to load two SWFs files from the same domain, does anyone have any examples and methods applying with allowDomain() that can be used to allow the SWFs to communicate and share data and functions.

ex: www.example.com
main.swf

about.swf (child)
contact.swf (child)

Most articles that I found it’s based on cross-domain which is not what I want.