Introduction to Cryptography with Open-Source Software

Chapter 1

Introduction to cryptography

This chapter “se ts the scene” for cryptogr aphy, and provides the basic security

context into which much of crypto graphy is used. In particular, the following

topics will be discussed:

• The need for information security.

• Basic definitions and terminology.

• Distinction between “secr e t key” (symmetric) and “public key” (asym-

metric) cryptosy stems.

• What it means to attack, and to break a cryptosystem, and some means

for doing so.

• Some cryptographic problems and protocols.

• Some simple pencil-a nd-paper systems, designed to provide examples for

the material of this chapter.

1.1 Hiding information: Confiden