Generation of MACs (Menu Indiv. Procedures \ Hash)

The dialog Message Authentication Code (MAC) shows how the digital fingerprint of a file is created using a hash function. The purpose of a MAC is to ensure authenticity.

Sender and receiver agree on a secret key and cryptographical hash function prior to message transmission. The sender links the message and the key (i.e. by appending) and hashes the created file. Then the hash value is transmitted together with the original message.

To check the authenticity, the receiver executes the same operations as the sender. He hashes the (received) message together with the secret key and compares the resulting hash value with the one he received. The message is authentic only if the two hash values are equal.