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

18.1 Symmetric cipher suites in TLS 1.3

TLS 1.3 specifies a set of so-called symmetric cipher suites that Alice and Bob can use to protect the data transmitted via the TLS Record protocol. Each symmetric cipher suite is a pair composed of two cryptographic algorithms:

  • An AEAD algorithm used for protecting the confidentiality and integrity of TLS records

  • A hash algorithm used within the HKDF function to derive TLS secrets and shared keys

The name of a TLS symmetric cipher suite starts with the string TLS and has the following format:


TLS_<AEAD algorithm>_<Hash algorithm>

where ¡AEAD algorithm and ¡Hash algorithm¿ are placeholders for specific algorithms. In addition, every cipher suite has a unique 2-byte identification value associated with it.

Table 18.1 shows the symmetric cipher suites that Alice and Bob can use according to the TLS 1.3 standard.

...
Cipher suite 2-byte identifier
TLS˙AES˙128˙GCM˙SHA256 0x13,0x01