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

Using the Online Certificate Status Protocol

In this section, we will learn about OCSP. First, we will learn what it is and how it works. Then, we will learn how to use OCSP on the command line and in C programs.

Understanding the Online Certificate Status Protocol

OCSP is a more modern method of certificate revocation checking that uses much less network traffic than CRL. When using OCSP, you don’t need to download large CRL files. Instead, it is possible to query an OCSP server, also known as an OCSP responder, about the status of a particular certificate. Similar to how CRLs are published by the issuer of a particular certificate, OCSP servers are also maintained by the certificate issuer.

When querying an OCSP responder, an OCSP client sends an ASN.1-encoded OCSP request, containing a list of certificates to check for revocation. The OCSP server responds with an ASN.1-encoded OCSP response, which contains the queried certificate statuses, the validity period of...