diff --git a/Charpter 21/TodoList/requirements.txt b/Charpter 21/TodoList/requirements.txt
old mode 100755
new mode 100644
index 184b58f..df5644f
--- a/Charpter 21/TodoList/requirements.txt	
+++ b/Charpter 21/TodoList/requirements.txt	
@@ -9,7 +9,7 @@ chardet==3.0.4
 click==6.7
 cloudpickle==0.5.3
 constantly==15.1.0
-cryptography==2.3.1
+cryptography==3.2
 cssselect==1.0.3
 dask==0.18.2
 decorator==4.3.0