[lisper]

> How would I know the hash? I'd have to save the individual key(hash) for every file I upload?

Yes, but that's no different from keeping any other kind of directory structure. And you can apply the same trick to the directory structure itself, so all you really need to keep is a "root hash" to your (encrypted) directory.

> Also, if I wanted to know if you had a specific file (and I had access to all your encrypted files) this would be trivial, correct?

What do you mean by "I had access to all your encrypted files"? If you've broken in to the server, everything is encrypted, including the directories. The only thing you can tell is whether a particular encrypted block corresponds to data that you already possess (or possessed at some time in the past). But that by itself tells you nothing.