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 X509v3 extensions?

X509v3 extensions are additional fields that can be added to an X.509 certificate. X509v3 extensions can impose constraints on certificate usage or provide additional information on the certificate. As an example, let’s go through the X509v3 extensions found in the website certificate:

  • Key Usage and Extended Key Usage: These extensions are constraints that limit certificate usage to certain purposes. It is up to the software that verifies the certificate to enforce X509v3 constraints. If the verifying software does not recognize or enforce certain X509v3 constraints, they will be ignored.
  • The CA:FALSE basic constraint: This extension asserts that the certificate must not be used to issue other certificates, meaning that the verification software must not consider such a certificate as an intermediate or root CA certificate.
  • Subject Key Identifier and Authority Key Identifier: Informational extensions that help to look...