update vkh

diff --git a/vkh b/vkh
index 0c9b7b9e6181a24673afcf4b87d850f405659308..3b64b87a871cd7652a4b6abc97d26f766c532e82 160000 (submodule)
--- a/vkh
+++ b/vkh
@@ -1 +1 @@
-Subproject commit 0c9b7b9e6181a24673afcf4b87d850f405659308
+Subproject commit 3b64b87a871cd7652a4b6abc97d26f766c532e82