diff --git a/messenger.py b/messenger.py
index 0c6a6a7..d797b59 100644
--- a/messenger.py
+++ b/messenger.py
@@ -21,8 +21,7 @@ class MessengerServer:
         return
 
     def signCert(self, cert):
-        raise Exception("not implemented!")
-        return
+        return self.server_signing_key.sign(cert, ec.ECDSA(hashes.SHA256()))
 
 class MessengerClient: