Fully or partially Decrypting Data with Multiple keys Is there any good paper or research carried out till now that a data is encrypted by a single key or onwer(user) and their are 2 or more decryption keys. One key can decrypt the entire data. Other keys decrypt partial data or a portion of data. A person having no key cannot decrypt the data but those having keys can fully or partially decrypt data based on the keys.
Functional encryption might fit your description; as far as I know it's still far from practical though.