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

Understanding the OpenSSL error queue

When running the rsa-encrypt program, many things can go wrong, such as the following:

  • The public key file may be corrupted or not contain a key. In this case, key loading will fail.
  • The public key file may contain a non-RSA key. In this case, key loading will succeed, but encryption will fail.
  • The input file may be too big. In this case, encryption will also fail but for another reason.

How do we handle such errors? Those OpenSSL functions that can fail usually indicate so by returning NULL, 0, or a negative number. Success is usually indicated by returning 1. Some functions also add an error to the OpenSSL error queue on failure.

The OpenSSL error queue is a container for errors that the OpenSSL library wants to report. Every thread of the process has its own OpenSSL error queue. The error queue does not require initialization or uninitialization; OpenSSL automatically handles it. Every thread starts with an empty error...