ABSTRACT
This chapter discusses various methods used to calculate message authentication codes and various hashing algorithms. Hash functions play the core role in message authentication where hash functions are iterative algorithms that operate in an arbitrary length message and return a fixed-length output. Message Authentication is the mechanism which lets the sending party and the receiving party maintains the integrity of the messages being shared. A hash function is a function which takes variable-length input of data and returns a fix-sized hash value. The hash generated has even distribution and is random. A message digest is a cryptographic hash function that takes any arbitrary length input and converts into an output of predefined fixed length known as hash or digest. The message Authentication code is a piece of authentication information used to verify the sending authority of the information and the integrity of the message. Hash message authentication code means applying a message authentication code algorithm using only cryptographic hash functions.
