Secure webservices?


I am needing to connect to a .NET webservice from flash, and it needs to be as secure as possible.

What are my options for doing this? I need it to be as absolutely secure as possible. Is just using HTTPS my best option? I have read a bit about the WS-Security specification - can this be used with Flash 8 / Actionscript 2.0? Does AS 3 add anything for this?

thanks in advance.