Functional Encryption: New Perspectives and Lower Bounds

Functional encryption is a new paradigm for public-key encryption that enables fine-grained control of access to encrypted data. It extends several previous notions, most notably identity-based encryption and provides, for instance, the ability to generate and release secret keys associated with a keyword that can decrypt only those documents that contain the keyword. More generally, functional encryption allows the owner of a "Master" secret key to release restricted secret keys that reveal a specific function of encrypted data. This stands in stark contrast to traditional encryption, where access to the encrypted data is all or nothing: namely, given the secret key, one can decrypt and read the entire plaintext, but without it, nothing about the plaintext is revealed at all (other than its length).