static function createStoreRequest(&$auth_request,&$attributeProvider,
                                               $attribute,$value,$openid)
   {
      if(!$auth_request){
         return null;
      }
      $signedAssertion=$attributeProvider->sign($openid,$attribute,$value);
      $store_request=new Auth_OpenID_AX_StoreRequest;
      $store_request->addValue($attribute,base64_encode($value));
      $store_request->addValue($attribute.'/signature',
                                           base64_encode($signedAssertion));
      if($store_request) {
         $auth_request->addExtension($store_request);
         return $auth_request;
      }
   }