1. Introduction

1.1 Tutorial's Goal

This tutorial aims to provide an introduction to key management, focusing specifically on public key cryptography. We will learn how to generate a pair of keys (public and private), and how to use these keys to encrypt and decrypt data.

1.2 Learning Outcomes

By the end of this tutorial, you will be able to:

• Understand the principles of public key cryptography.
• Generate a pair of keys.
• Use the keys to encrypt and decrypt data.

1.3 Prerequisites

Basic knowledge of Python programming is required as we will be using Python for our examples and exercises.

2. Step-by-Step Guide

2.1 Concepts

Public key cryptography, also known as asymmetric cryptography, uses a pair of keys: a public key, which is shared freely, and a private key, which is kept secret. Anyone can encrypt a message using the public key, but only the holder of the private key can decrypt it.

2.2 Best Practices

• Always keep your private key secret and secure.
• Use strong and random keys.
• Regularly update your keys.

3. Code Examples

3.1 Generating Key Pair

We will use rsa package to generate and use RSA keys in Python.

from rsa.key import newkeys

# generate public and private keys
publicKey, privateKey = newkeys(2048)

print(publicKey)
print(privateKey)

This will print out the public and private keys. The number 2048 is the key size in bits and it is recommended to use a high value for stronger keys.

3.2 Encryption and Decryption

Now let's encrypt and decrypt a message.

import rsa

message = 'Hello, World!'

# Encryption
encrypted_message = rsa.encrypt(message.encode(), publicKey)
print(encrypted_message)

# Decryption
decrypted_message = rsa.decrypt(encrypted_message, privateKey)
print(decrypted_message.decode())

The encrypt function takes the message and the public key, and returns the encrypted message. The decrypt function takes the encrypted message and the private key, and returns the decrypted message.

4. Summary

In this tutorial, we have covered the basics of public key cryptography, including generating a key pair and using these keys to encrypt and decrypt data. We have also discussed some best practices in key management.

For further learning, you may want to explore more advanced topics such as key exchange protocols and digital signatures.

5. Practice Exercises

5.1 Exercise 1: Key Generation

Write a function that generates and returns a pair of keys.

5.2 Exercise 2: Encryption

Write a function that takes a message and a public key, and returns the encrypted message.

5.3 Exercise 3: Decryption

Write a function that takes an encrypted message and a private key, and returns the decrypted message.

Remember to test your functions to make sure they work as expected!

For further practice, you could try to implement these exercises in another programming language, or explore other types of public key cryptography such as ElGamal or ECC.