CCM mode

CCM mode (Counter with CBC-MAC) is a mode of operation for cryptographic block ciphers. It is an authenticated encryption algorithm designed to provide both authentication and confidentiality. CCM mode is only defined for block ciphers with a block length of 128 bits. In RFC 3610, it is defined for use with AES.

Encryption and authentication

As the name suggests, CCM mode combines the well-known counter mode of encryption with the well-known CBC-MAC mode of authentication. The key insight is that the same encryption key can be used for both, provided that the counter values used in the encryption do not collide with the (pre-)initialization vector used in the authentication. A exists for this combination, based on the security of the underlying block cipher. The proof also applies to a generalization of CCM for any size block cipher, and for any size cryptographically strong pseudo-random function (since in both counter mode and CBC-MAC, the block cipher is only ever used in one direction).

CCM mode was designed by Russ Housley, Doug Whiting and Niels Ferguson. At the time CCM mode was developed, Russ Housley was employed by RSA Laboratories.

A minor variation of the CCM, called CCM*, is used in the ZigBee standard. CCM* includes all of the features of CCM and additionally offers encryption-only and integrity-only capabilities.

Performance

CCM requires two block cipher encryption operations per each block of encrypted and authenticated message and one encryption per...
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