How to Secure wcf Services between two applications

Question

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 my wcf services to be acccessed 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.

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