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 encrypt and decrypt with AES on the command line

We are going to encrypt a file using the openssl command-line tool.

Let’s generate a sample file:

$ seq 1000 >somefile.txt

Using our knowledge of the symmetric encryption concepts, we are choosing the following parameters for our encryption:

  • Cipher: AES-256
  • Operation mode: CBC (we should have chosen GCM, but that mode is not supported by the command-line tool)
  • Padding type: standard block padding

How can we find out how to encrypt the command line from the documentation? We can begin with the openssl tool man page:

$ man openssl

On that man page, we can see different subcommands that the openssl tool supports. From the man page, we can figure out that we need the enc subcommand. We can then refer to the openssl-enc man page for documentation on the enc subcommand:

$ man openssl-enc

From the openssl-enc man page, we can figure out which parameters the subcommand needs. We see...