Block Cipher Modes of Operation - Other Modes and Other Cryptographic Primitives

Other Modes and Other Cryptographic Primitives

Many more modes of operation for block ciphers have been suggested. Some have been accepted, fully described (even standardized), and are in use. Others have been found insecure, and should never be used. Still others don't categorize as confidentiality, authenticity, or authenticated encryption - for example Key Feedback Mode (KFM) and AES-hash.

NIST maintains a list of proposed modes for block ciphers at Modes Development.

Disk encryption often uses special purpose modes specifically designed for the application. Tweakable narrow-block encryption modes (LRW, XEX, and XTS) and wide-block encryption modes (CMC and EME) are designed to securely encrypt sectors of a disk. (See disk encryption theory)

Block ciphers can also be used in other cryptographic protocols. They are generally used in modes of operation similar to the block modes described here. As with all protocols, to be cryptographically secure, care must be taken to build them correctly.

There are several schemes which use a block cipher to build a cryptographic hash function. See one-way compression function for descriptions of several such methods.

Cryptographically secure pseudorandom number generators (CSPRNGs) can also be built using block ciphers.

Message authentication codes (MACs) are often built from block ciphers. CBC-MAC, OMAC and PMAC are examples.

Authenticated encryption also uses block ciphers as components. It means to both encrypt and MAC at the same time. That is to both provide confidentiality and authentication. IAPM, CCM, CWC, EAX, GCM and OCB are such authenticated encryption modes.