Definition: MAC

(1) For Apple's Mac, see Mac computer.

(2) For the built-in hardware ID, see MAC address.

(3) For the network protocol layer, see MAC layer.

(4) See moves-adds-changes and mandatory access control.

(5) (Multiply And aCcumulate) See matrix multiplication.

(6) (Multiplexed Analog Components) A video format that was analog video and digital audio. See HD analog formats.

(7) (Mission Assurance Category) See DOD cyberspace glossary.

(8) (Medicare Administrative Contractor) See healthcare IT.

(9) (Message Authentication Code) A number computed from the contents of a text message that is used to prove the integrity of a message. The MAC is a checksum that is computed using an algorithm based on the DES or AES ciphers, which use a secret key. The MAC is then sent with the message. The recipient recomputes the MAC at the other end using the same algorithm and secret key and compares it to the one that is sent. If they are the same, it is assumed that the message has not been tampered with.

A MAC is like a digital signature, except that a secret key is used rather than a private key. Also known as the U.S. Government Standard Data Authentication Code (FIPS PUB 113). See digital signature, cryptography, DES and AES.