Hide Post from other authors

Hello,

I’ve scoured the internet looking for this but can’t seem to find it anywhere, I may just be wording a simple question strangely.

I have a blog with multiple contributors as authors. Is there a way to set a post by Author A to be not visible to the public as well as not visible to Author B? Preferably without passwords? Both authors should be able to post to the normal blog but also keep super seekret diaries that are hidden from each other.

Can anyone suggest a plugin or another forum post suggesting an answer, or even just an answer?

Thanks

Tom