Message Authentication Codes
DOI link for Message Authentication Codes
Message Authentication Codes book
This chapter shows how to achieve message integrity by using cryptographic techniques to detect any spoofed messages or any tampering of messages sent over an unprotected communication channel. One might mistakenly think that encryption solves the problem of message authentication. This is due to the fuzzy, and incorrect, reasoning that since a ciphertext completely hides the contents of the message, an adversary cannot possibly modify an encrypted message in any meaningful way. The aim of a message authentication code is to prevent an adversary from modifying a message sent by one party to another, or from injecting a new message, without the receiver detecting that the message did not originate from the intended party. The crucial point is that what constitutes a meaningful message is entirely application dependent.