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

7.3 The Diffie-Hellman key-exchange protocol

Alice and Bob communicate over an insecure channel. They can establish a shared secret K using the following protocol steps [49]:

  1. Alice and Bob publicly agree on a cyclic group 𝔾 and a corresponding generator g. Very often, this step is performed out of band long before the actual key agreement. For example, 𝔾 and g might be specified in a public document.

  2. Alice chooses a natural number α, where 1 < α < N, where N is the order of 𝔾. α is Alice’s private key SKAlice. She must not disclose this number to any other party.

  3. Bob does the same as Alice: he independently chooses a number 1 < β < N as his private key SKBob.

  4. Alice computes A = gα in G and sends A to Bob. The number A (together with G and g) can be seen as Alice’s public key: PKAlice = (g,G,A).

  5. Bob computes B = gβ in G and sends B to Alice. The number B (together with G and g) can be seen...