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.
Convergent encryption
Convergent encryption, also known as content hash keying, is a cryptosystem that produces identical ciphertext from identical plaintext files. This has applications in cloud computing to remove duplicate files from storage without the provider having access to the encryption keys. The combination of deduplication and convergent encryption was described in a backup system patent filed by Stac Electronics in 1995. This combination has been used by Farsite, Permabit, Freenet, MojoNation, GNUnet, flud, and the Tahoe Least-Authority File Store.