We introduce the concepts of cryptography-based security step by step.
The first step is the cryptographic algorithms—ciphers and cryptographic hashes—that are introduced in this section. They are not a solution in themselves, but rather building blocks from which a solution
can be built. Cryptographic algorithms are parameterized by keys, and
Section 8.2 addresses the problem of distributing the keys. In the next step
(Section 8.3), we describe how to incorporate the cryptographic building blocks into protocols that provide secure communication between
participants who possess the correct keys. Finally, Section 8.4 examines
several complete security protocols and systems in current use.