function verifyAssertion(&$attributeVerifier,$response)
   {
      $ax_resp=Auth_OpenID_AX_FetchResponse::fromSuccessResponse($response);
      if($ax_resp instanceof Auth_OpenID_AX_FetchResponse){
         $ax_args=$ax_resp->getExtensionArgs();
         if($ax_args) {
            $value=base64_decode($ax_args['value.ext1.1']);
            if($attributeVerifier->verify($value)){
               return base64_decode($ax_args['value.ext0.1']);
            } else {
               return null;
            }
         } else {
            return null;
         }
      } else {
         return null;
      }
   }