Yes exactly. key = f(data); upload(encrypt(data, key)); store_key(filename, key); Which is to say that every file has a globally 1-to-1 mapping to its encry

Yes exactly. key = f(data); upload(encrypt(data, key)); store_key(filename, key); Which is to say that every file has a globally 1-to-1 mapping to its encrypted version. I'm not sure how they are storing the (User, [(Filename,Key)]) data, but this is ideally encrypted on a per user basis, making any sort of per-user lookup attacks moot.