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

11.5 Message authentication codes

If Alice wants to securely transmit a message m to Bob, she must use a so-called Message Authentication Code (MAC) to prevent Eve from tampering with that message. More precisely, a MAC prevents Mallory from doing the following:

  • Modifying m without Bob noticing it

  • Presenting Bob a message m′ generated by Mallory, mm, without Bob noticing that m′ was not sent by Alice

Therefore, a MAC helps us to achieve the two security objectives integrity protection and message authentication (see Chapter 2, Secure Channel and the CIA Triad and Chapter 5, Entity Authentication). Note that a MAC cannot prevent the tampering itself, nor can it prevent message replay. The active attacker Mallory can always manipulate the genuine message m, or present Bob with the message m′ and pretend that it was sent by Alice. A MAC only gives Bob the ability to detect that something went wrong during the transmission of the message he...