# A Basic Cryptosystem

Let's understand what a cryptosystem is in this lesson.

## We'll cover the following

## Introduction

In general, a cryptosystem consists of three types of protocols for the following functions:

- Key generation: Creating a single or a pair of secret key(s).
- Encryption: There’s a protocol $e(\cdot)$ that transforms cleartext $m$ into ciphertext $c$.
- Decryption: There’s a protocol $d(\cdot)$ that transforms the ciphertext $c$ back to its corresponding cleartext $m.$

The figure below shows the scheme of a basic cryptosystem.

### Figure 1

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