See Also: MACTripleDES Members
A MAC can be used to determine whether a message sent over an insecure channel has been tampered with, provided that the sender and receiver share a secret key. The sender computes the MAC for the original data, and sends both as a single message. The receiver recomputes the MAC on the received message, and checks that the computed MAC matches the transmitted MAC.
Any change to the data or the MAC results in a mismatch, because knowledge of the secret key is required to change the message and reproduce the correct MAC. Therefore, if the codes match, the message is authenticated.
System.Security.Cryptography.MACTripleDES uses a key that is 16 or 24 bytes long, and produces a hash sequence that is 8 bytes long.