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TLS Cryptography In-Depth

TLS Cryptography In-Depth

By : Dr. Paul Duplys, Dr. Roland Schmitz
4.7 (3)
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TLS Cryptography In-Depth

TLS Cryptography In-Depth

4.7 (3)
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)
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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

13.1 TLS client state machine

Appendix A of RFC 8446, the IETF specification of TLS 1.3, summarizes valid states and state transitions for TLS 1.3 server and client. The client state machine is shown in Figure 13.1. Labels in square brackets indicate actions the client performs only under specific circumstances. Label k = x indicates that the key k is set to value x.

Figure 13.1: State machine and state transitions of a TLS 1.3 client

Figure 13.1: State machine and state transitions of a TLS 1.3 client

Client Bob starts the TLS handshake by sending the ClientHello message to server Alice. If Bob and Alice have agreed upon a secret key in a previous TLS session, Bob may use this key to encrypt early data.

Bob then transitions into state WAIT˙SH, denoted by WSH, where he waits for the ServerHello message from Alice. If Bob’s ClientHello contains parameter values that Alice does not support, she replies with a HelloRetryRequest message, thereby making Bob switch back to the initial state and re-send ClientHello with different parameters...

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