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

Comparing OpenSSL with GnuTLS

GnuTLS is a free software TLS library that was created for the needs of the GNU Project. When GnuTLS was created, most applications of the GNU Project were distributed under the GPL 2.0 license, which is incompatible with the old OpenSSL license. The authors of the GPL 2.0 licensed software had to include a licensing exception if they wished to link with OpenSSL. GnuTLS was originally licensed under LGPL 2.0, so it did not require such licensing exceptions.

Currently, GnuTLS is licensed under LGPL 2.1. This license allows users to use the library in free and open source software (FOSS) projects. It is also allowed to use the library in closed source projects, but with certain conditions, such as only dynamic linking.

GnuTLS does not include cryptography, big-number arithmetic functionality, and some other functionality that OpenSSL includes. Instead, GnuTLS uses other libraries from the GNU ecosystem that provide the needed functionality: Nettle for cryptography, GMP for big-number arithmetic, Libtasn1 for ASN.1 (short for Abstract Syntax Notation One), and so on.

An interesting feature of GnuTLS is that it supports not only X.509 certificates but also OpenPGP certificates. Unlike an X.509 certificate, which is signed by its issuer at the time of being issued, an OpenPGP certificate supports the so-called web of trust, can have multiple signatures, and signatures can be added once the certificate has been issued. Unfortunately, OpenPGP certificates have not gained popularity for usage in TLS connections.

Apart from OpenPGP certificate support, GnuTLS and its crypto library, Nettle, support fewer crypto algorithms than OpenSSL, and performance-wise, they are a bit slower than OpenSSL. GnuTLS and Nettle, however, support all popular algorithms.

Should you choose OpenSSL or GnuTLS? I recommend that you choose GnuTLS if you are developing GPL-licensed software; otherwise, choose OpenSSL.

Another competitor to OpenSSL is the NSS library, which we will discover in the next section.