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)
1
Part 1: Introduction
3
Part 2: Symmetric Cryptography
8
Part 3: Asymmetric Cryptography and Certificates
12
Part 4: TLS Connections and Secure Communication
16
Part 5: Running a Mini-CA

MAC, encryption, and the Cryptographic Doom Principle

When combining a MAC with encryption, one of the following schemes is used:

  • Encrypt-then-MAC (EtM): Here, the plaintext is encrypted, then the MAC is calculated on the ciphertext and sent together with the ciphertext.
  • Encrypt-and-MAC (E&M): Here, the plaintext is encrypted, but the MAC is calculated on the plaintext instead of the ciphertext. The ciphertext and the MAC are then sent together.
  • MAC-then-Encrypt (MtE): Here, the MAC is calculated on the plaintext. Concatenation of the plaintext and the MAC is then encrypted.

On the receiving side, the EtM scheme allows you to check the authenticity of the encrypted message before the decryption operation. The other two schemes require decryption of the whole plaintext before the MAC can be verified.

Security researchers regard EtM as the most secure scheme, provided that a strong and unforgeable MAC function is used. From a security point of view, it makes...