How to verify that library assemblies originate from a given Web site?

Question

How would the following solution be implemented? Would you need to put this code in each library assembly or just in the main assembly that is determining whether it is safe to call the library assembly based on whether or not it originates from a given intranet Web site? Also, who should call the CheckSite method - each library assembly or the main app? Here is the example and solution from a practice exam for the C# Specialist Exam 70-483 that I am referring to:

You are an application developer for a company. You are creating an application on the company’s Web server that will manipulate confidential data from business partners. The application relies on many library assemblies in the company intranet to complete its work. You are required to verify that every assembly originates from the same intranet Web site. Which code should you use to verify the current assembly originates from the company intranet?

public bool CheckSite () {
    SiteMembershipCondition site = new
        SiteMembershipCondition( “http://intranet.company.com” );
    return site.Check( Assembly.GetCallingAssembly().Evidence );
}