Book Image

Demystifying Cryptography with OpenSSL 3.0

By : Alexei Khlebnikov
Book Image

Demystifying Cryptography with OpenSSL 3.0

By: Alexei Khlebnikov

Overview of this book

Security and networking are essential features of software today. The modern internet is full of worms, Trojan horses, men-in-the-middle, and other threats. This is why maintaining security is more important than ever. OpenSSL is one of the most widely used and essential open source projects on the internet for this purpose. If you are a software developer, system administrator, network security engineer, or DevOps specialist, you’ve probably stumbled upon this toolset in the past – but how do you make the most out of it? With the help of this book, you will learn the most important features of OpenSSL, and gain insight into its full potential. This book contains step-by-step explanations of essential cryptography and network security concepts, as well as practical examples illustrating the usage of those concepts. You’ll start by learning the basics, such as how to perform symmetric encryption and calculate message digests. Next, you will discover more about cryptography: MAC and HMAC, public and private keys, and digital signatures. As you progress, you will explore best practices for using X.509 certificates, public key infrastructure, and TLS connections. By the end of this book, you’ll be able to use the most popular features of OpenSSL, allowing you to implement cryptography and TLS in your applications and network infrastructure.
Table of Contents (20 chapters)
Part 1: Introduction
Part 2: Symmetric Cryptography
Part 3: Asymmetric Cryptography and Certificates
Part 4: TLS Connections and Secure Communication
Part 5: Running a Mini-CA

What are message digests and cryptographic hash functions?

A message in cryptography is any piece of data, big or small, that is processed by a cryptographic algorithm.

A cryptographic hash function is an algorithm that maps a message of arbitrary size to a relatively short (for example, 256 bits) fixed-size array of bits. This fixed-size bit array is called a message digest or a cryptographic hash.

In other words, a message digest is the output of a cryptographic hash function. As we mentioned in the previous chapter, we can say that a message digest is a cryptographically strong checksum.

A good cryptographic hash function has the following properties:

  • It is deterministic, meaning that processing the same message must always yield the same message digest.
  • It is irreversible, meaning that it must be impossible or extremely difficult to recover the original message by its digest. The only way to reverse the hash should be brute force and it must be too computationally...