5.1. Introduction

As we pointed out in Chapter 1, cryptography tends to guard sensitive data from unauthorized access. We shortly describe some algorithms that achieve this goal. We restrict ourselves only to public-key algorithms. In practice, however, public-key algorithms are used in tandem with secret-key algorithms. In this chapter, we describe only the basic routines to which are input mathematical entities like integers, points in finite fields or on curves. Message encoding will be dealt with in Chapter 6.