Book Image

TLS Cryptography In-Depth

By : Dr. Paul Duplys, Dr. Roland Schmitz
Book Image

TLS Cryptography In-Depth

By: Dr. Paul Duplys, Dr. Roland Schmitz

Overview of this book

TLS is the most widely used cryptographic protocol today, enabling e-commerce, online banking, and secure online communication. Written by Dr. Paul Duplys, Security, Privacy & Safety Research Lead at Bosch, and Dr. Roland Schmitz, Internet Security Professor at Stuttgart Media University, this book will help you gain a deep understanding of how and why TLS works, how past attacks on TLS were possible, and how vulnerabilities that enabled them were addressed in the latest TLS version 1.3. By exploring the inner workings of TLS, you’ll be able to configure it and use it more securely. Starting with the basic concepts, you’ll be led step by step through the world of modern cryptography, guided by the TLS protocol. As you advance, you’ll be learning about the necessary mathematical concepts from scratch. Topics such as public-key cryptography based on elliptic curves will be explained with a view on real-world applications in TLS. With easy-to-understand concepts, you’ll find out how secret keys are generated and exchanged in TLS, and how they are used to creating a secure channel between a client and a server. By the end of this book, you’ll have the knowledge to configure TLS servers securely. Moreover, you’ll have gained a deep knowledge of the cryptographic primitives that make up TLS.
Table of Contents (30 chapters)
1
Part I Getting Started
8
Part II Shaking Hands
16
Part III Off the Record
22
Part IV Bleeding Hearts and Biting Poodles
27
Bibliography
28
Index

17.7 An experiment with the OpenSSL s_client

We use the OpenSSL s˙client again to see the TLS record protocol at work. For this purpose, we use the OpenSSL Docker container from the previous chapter.

17.7.1 Getting started

To start the container, execute the following command:

$ docker container run --rm -it openssl310

Once the Docker container is up and running, it will give you a command-line prompt similar to the following one, where you can call the s˙client tool:

root@07c3ba265c69:/opt/openssl#

17.7.2 Retrieving a website via TLS

Our goal is to retrieve a web page from the server in order to see what the TLS records look like. To demonstrate this, we will use the website www.cr.yp.to of the American-German mathematician and cryptographer Daniel (Dan) Bernstein, the author of the x25519 elliptic curve.

HTTP uses a GET request method to retrieve a web page. The GET request specifies the path of the page to be retrieved and the HTTP version. The standard HTTP version...