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Block Cipher Modes

A block cipher mode, or mode, for short, is an algorithm that features the use of a symmetric key block cipher algorithm to provide an information service, such as confidentiality or authentication.

With the advent of new block ciphers, such as the Advanced Encryption Standard (AES), there is a need to update long-standing modes of operation and an opportunity to consider the development of new modes.

Currently, NIST has approved twelve modes of the approved block ciphers in a series of special publications. As summarized on the Current Modes page, there are six confidentiality modes (ECB, CBC, OFB, CFB, CTR, and XTS-AES), one authentication mode (CMAC), and five combined modes for confidentiality and authentication (CCM, GCM, KW, KWP, and TKW).

Several other modes have been submitted to NIST for consideration; the submission documents are available at the Modes Development page. NIST welcomes public input on whether to approve any of these modes. Comments may be submitted to