Allow contributors to password protect posts

Hello,

i’d like to allow contributors to choose a password for their posts.

By default, as I figured out, only the “author” role is able to change the visibility settings in the metabox.

Unfortunately I couldnt find anything in the Codex, which user permission flag is responsible for allowing to change the visibility settings.
Because then I could just add this individual flag to the contributor role.

Important: I dont want to allow contributors to publish posts themselves (like authors), they should just be able to choose a password for each post.

Thank you, best wishes