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

How to sign and verify a signature on the command line

OpenSSL provides several subcommands for signing and verifying signatures. Let’s take a look:

  • The deprecated RSA-specific openssl rsautl subcommand.
  • The openssl dgst subcommand: This is usually used for message digest calculation but can also be used to sign the produced digests. This means that it cannot be used to sign PureEdDSA because that signature algorithm does not sign digests.
  • The openssl pkeyutl subcommand: This subcommand can be used to sign with any signature algorithm supported by OpenSSL. Before OpenSSL 3.0, openssl pkeyutl did not support signing long inputs; the user had to make the message digest before signing. Since OpenSSL 3.0, openssl pkeyutl supports both “raw input,” as it is called in the documentation, and a message digest as input.

We are going to use the openssl pkeyutl subcommand for our examples. Its documentation can be found on the openssl-pkeyutl man page...