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)
1
Part 1: Introduction
3
Part 2: Symmetric Cryptography
8
Part 3: Asymmetric Cryptography and Certificates
12
Part 4: TLS Connections and Secure Communication
16
Part 5: Running a Mini-CA

How to calculate the message digest programmatically

We are going to implement the digest program that will calculate SHA3-256 message digest of a file.

Our digest program will receive only one command-line argument: the name of the input file to be hashed.

As with symmetric encryption in the previous chapter, let’s make a high-level plan for calculating the message digest:

  1. First, we must initialize the message digest calculation context.
  2. Then, we must feed data to the message digest calculation context chunk by chunk, reading chunks from the input file.
  3. Next, we must finalize the calculation and get the message digest.
  4. Finally, we must print the calculated message digest to stdout.

Similar to symmetric encryption, OpenSSL contains the new EVP API and the old, deprecated low-level API for message digest calculation. The functions of the EVP API start with the EVP_ prefix, while the functions of the low-level API start with hash function-specific...