CCM mode (original) (raw)

CCM mode (counter with cipher block chaining message authentication code; 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. The nonce of CCM must be carefully chosen to never be used more than once for a given key.This is because CCM is a derivation of counter (CTR) mode and the latter is effectively a stream cipher.