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

18.6 Mandatory-to-implement cipher suites

For compatibility purposes, every TLS endpoint must fulfill a minimum set of requirements. To ensure this, Chapter 9 in RFC 8446 defines three types of compliance requirements:

  1. Mandatory-to-implement cipher suites

  2. Mandatory-to-implement TLS extensions

  3. Protocol invariants that every TLS endpoint and middlebox must follow

If there is no dedicated application profile standard that prescribes different algorithms, TLS 1.3 specification requires a TLS endpoint to implement cipher suites given in Table 18.2. Note, however, the difference in the requirement level for the specific cipher suites. The exact meaning of the capital words MUST and SHOULD is defined in IETF RFC 2119, Key words for use in RFCs to Indicate Requirement Levels.

The term MUST (or its equivalents, REQUIRED or SHALL) means that the requirement is absolutely mandatory – there is no room for exceptions. In contrast, the term SHOULD (or its equivalent, RECOMMENDED...