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

17.1 TLS Record protocol

The purpose of the TLS Record protocol is to cryptographically protect data in transit using the shared secret keys that Alice and Bob established using the TLS Handshake protocol. More precisely, the Record protocol takes a message that Alice wants to send, partitions the message into one or multiple blocks, protects these records by cryptographic means, and transmits the protected records. When Bob receives this information, the Record protocol ensures that the records are verified regarding their authenticity and integrity, decrypted using the correct key, and reassembled into the original message sent by Alice.

Every TLS record has one of the following four types:

  • handshake

  • application_data

  • alert

  • change˙cipher˙spec

Having types is beneficial because this way multiple higher-level protocols can use the same record layer. If Alice or Bob receive an unexpected record type, they terminate their TLS session and transmit the unexpected˙message...