2
Secure Channel and the CIA Triad
In this chapter, we discuss the fundamental objective of cryptography and computer security, namely enabling two parties to communicate securely over an insecure communication channel. As we will see shortly, this is not an easy task to accomplish because the communication needs to be secure against both passive and active attackers.
But how can we achieve security if the attacker is allowed to listen to the entire communication and even manipulate the messages sent over the channel? And what are the fundamental design principles that we must follow to build systems that can protect that communication?
To answer these questions, we will cover the most important cryptographic definitions, essential design principles, and central cryptographic goals. We will show how these goals can be achieved in principle, leaving the technical details for the chapters to follow. Finally, we will introduce the notion of a secure channel, which lies at the heart of TLS...