// Enabling the authentication service, all other WCF services in your web application will have to compatible with ASP.NET
    // http://msdn.microsoft.com/en-us/library/aa702682.aspx
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    public class PrimeService : IPrimeService
    {
        public int NextPrime(int n)
        {
            // HttpContext.Current.User.Identity.IsAuthenticated is true because 
            // Application_AuthenticateRequest set the authenticated user into the context
            if (!HttpContext.Current.User.Identity.IsAuthenticated)
            {
                throw new FaultException<SecurityAccessDeniedException>(new SecurityAccessDeniedException());
            }
            // calculate prime number
        }
    }