Access control for posts and attchments

Hi,

I am looking for a good way to restrict:

– certain posts. Only login or above certain level users can access. This seems can be done by some role management plug in. But I am open to any suggestion.

– certain files. This is my bigger problem: is there a way I can upload a file and only allow certain users to download? Hiding the link is not good enough, I suppose the search engine still can get to it.

Thanks for any suggestion.

dc