Disk encryption software
Disk encryption generally refers to wholesale encryption that operates on an entire volume mostly transparently to the user, the system, and applications. This is generally distinguished from file-level encryption that operates by user invocation on a single file or group of files, and which requires the user to decide which specific files should be encrypted. Disk encryption usually includes all aspects of the disk, including directories, so that an adversary cannot determine content, name or size of any file. It is well suited to portable devices such as laptop computers and thumb drives which are particularly susceptible to being lost or stolen. If used properly, someone finding a lost device cannot penetrate actual data, or even know what files might be present.
Functional encryption
More precisely, a functional encryption scheme for a given functionality formula_1 consists of the following four algorithms:Functional encryption generalizes several existing primitives including Identity-based encryption (IBE) and Attribute-based encryption (ABE).
In the IBE case, define formula_12 to be equal to formula_9 when formula_7 corresponds to an identity that is allowed to decrypt, and formula_15 otherwise.
Similarly, in the ABE case, define formula_16 when formula_7 encodes attributes with permission to decrypt and formula_15 otherwise.