I would first challenge the question a little bit. I don't know what a “top secret” cloud is. If a cloud is a shared resource that people have access to for lots of good reasons, then in order to make that top secret you have to do it with access control. Access control is basically just a system where your top secret data is stored and you limit the access to it in some way.
On June 7th, 2022. See this statement in context.