Update readme

Author: JoepdeJong

README.md

@@ -1,2 +1,18 @@
 # passes
+
 Wallet passes integration
+
+## Convery key to legacy
+
+Make sure to convert the apple key to AES-256-CBC:
+https://stackoverflow.com/a/72600724/4858692
+
+```sh
+# in 3.x.x
+openssl pkcs12 -in old -nodes -provider legacy -provider default -out temp && openssl pkcs12 -in temp -export -out new
+# or simpler
+openssl pkcs12 -in old -nodes -legacy -out temp && openssl pkcs12 -in temp -export -out new
+
+# in 1.x.x
+openssl pkcs12 -in old -nodes -out temp && openssl pkcs12 -in temp -export -descert -out new
+```