Principal Propagation SOAP-RFC

Hi,

I have a scenario where I have to propagate the user context from a mobile app to my ECC system.

MobileApp -> PI -> ECC

SOAP -> RFC

I have made principal propagation settings as per the blog:

http://scn.sap.com/community/pi-and-soa-middleware/blog/2007/01/16/principal-propagation-in-sap-xi

I have made the PI and ECC system as trusted systems.

So in my receiver RFC adapter why should I have to give basic authentication details to connect to the ECC system?

And there is no place in my receiver RFC adapter where I can specify that the system should use certificates.

Can anyone clarify the concept?

Thanks

Shakthi