How to secure wcf services between two application hosted on same machine

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security

ASP.NET4

WCFServices

I am having Two Application. Assume First application name is AAA and second application name is BBB. The Application with name BBB are having wcf services. Now i dont want  to access my wcf services to application AAA . In other words I want to prevent the application AAA consuming my wcf services . These two application are hosted on the same computer. Apart from authentication and authorization what else can be used. Any url or help is much appreciated.

For better understanding I have attached my image

What I have tried:

I have explored with user id and password. But i am not looking for this as my apllication doest fit this requirement