2.6 Secure channels and the CIA triad

So far, we have discussed three important cryptographic goals: confidentiality, integrity, and authentication. For the purposes of this book, the term secure system can be defined as a system that provides a combination of those three goals. Taken together, confidentiality, integrity, and authentication are oftentimes referred to as the CIA triad.

Some modern-day scholars and newer books on computer security use the term availability instead of authentication for the A in CIA. In this book, we deliberately stick to the classical definition. The main reason for this is that, strictly speaking, availability belongs to the realm of security engineering, not cryptography. While cybersecurity threats such as denial-of-service attacks are sometimes discussed in cryptography-related literature, a cryptographic protocol and mechanism by itself is in principle unable to guarantee availability. As a rather simple example, any cryptographic protocol assumes...