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

19.6 Attacks on encryption schemes

If Eve attacks an encryption scheme utilizing available ciphertext, she can try to recover either the plaintext of the encrypted messages or the secret key itself used by the encryption scheme.

Recovery of the secret key is typically considered a stronger attack (or, equivalently, a more severe security compromise) than deducing plaintext from the ciphertext. As an example, if Alice and Bob use some standard, pre-defined messages that significantly vary in size – that is, to an extent that is not compensated by padding – Eve can easily guess the plaintext for a given ciphertext even if the encryption scheme is perfectly secret.

On the other hand, to determine the secret key, Eve must find statistical relations between the plaintext and the ciphertext. As far as we know, this is practically impossible for standardized ciphers, let alone for perfectly secret encryption schemes.

19.6.1 Brute-force attack

A brute-force attack is simply an...