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 with RSA programmatically

OpenSSL 3.0 provides the following APIs for RSA encryption:

  • A legacy API with the RSA_ prefix and the RSA_public_encrypt() function. This API has been deprecated since OpenSSL 3.0, so we are not going to use it.
  • The EVP_PKEY API, particularly the EVP_PKEY_encrypt() function. We are going to use this API.
  • The EVP_Seal API. This is a hybrid encryption API that generates a session key, encrypts the session key with RSA, and then encrypts the user data with the session key. This API contains the EVP_SealInit(), EVP_SealUpdate(), and EVP_SealFinal() functions, which work similarly to EVP_EncryptInit(), EVP_EncryptUpdate(), and EVP_EncryptFinal(). EVP_SealUpdate() is just #define for EVP_EncryptUpdate(). There are also the corresponding EVP_Open functions for decrypting the sealsEVP_OpenInit(), EVP_OpenUpdate(), and EVP_OpenFinal(). Unfortunately, the EVP_Seal API is rather inflexible. It supports only RSA encryption of...