private ZPrincipal GetPrincipal(HttpActionContext actionContext)
 {
     try
     {
         string authHeader = actionContext.Request.Headers.GetValues(AuthConfiguration.AuthHeader).First();
         var    result     = Rijndael.Decrypt(authHeader, Rijndael.GetRandomKeyText());
         return(JsonConvert.DeserializeObject <ZPrincipal>(result));
     }
     catch (Exception)
     {
         return(null);
     }
 }