Mastering Blockchain - Second Edition

MACs using block ciphers

With this approach, block ciphers are used in the Cipher Block Chaining (CBC) mode in order to generate a MAC. Any block cipher, for example AES in the CBC mode, can be used. The MAC of the message is, in fact, the output of the last round of the CBC operation. The length of the MAC output is the same as the block length of the block cipher used to generate the MAC.

MACs are verified simply by computing the MAC of the message and comparing it to the received MAC. If they are the same, then the message integrity is confirmed; otherwise, the message is considered altered. It should also be noted that MACs work like digital signatures, however they cannot provide non-repudiation service due to their symmetric nature. ...