Real-World Cryptography

3 Message authentication codes

This chapter covers

• Message authentication codes (MACs)
• The security properties and the pitfalls of MACs
• The widely adopted standards for MACs

Mix a hash function with a secret key and you obtain something called a message authentication code (MAC), a cryptographic primitive to protect the integrity of data. The addition of a secret key is the foundation behind any type of security: without keys there can be no confidentiality, and there can be no authentication. While hash functions can provide authentication or integrity for arbitrary data, they do that thanks to an additional trusted channel that cannot be tampered with. In this chapter, you will see how a MAC can be used to create such a trusted channel ...