diff --git a/webapp/services/callback/InAppPurchase.php b/webapp/services/callback/InAppPurchase.php
index 8f3cae19..fa4cb5d1 100644
--- a/webapp/services/callback/InAppPurchase.php
+++ b/webapp/services/callback/InAppPurchase.php
@@ -204,4 +204,9 @@ class InAppPurchase {
         $this->_rspOk();
     }
 
+    private function verifySign()
+    {
+
+    }
+
 }