Book Image

Cryptography Engineering

By : Niels Ferguson‚ÄØ, Tadayoshi Kohno, Bruce Schneier
Book Image

Cryptography Engineering

By: Niels Ferguson‚ÄØ, Tadayoshi Kohno, Bruce Schneier

Overview of this book

Cryptography is vital to keeping information safe, in an era when the formula to do so becomes more and more challenging. Written by a team of world-renowned cryptography experts, this essential guide is the definitive introduction to all major areas of cryptography: message security, key negotiation, and key management. You'll learn how to think like a cryptographer. You'll discover techniques for building cryptography into products from the start and you'll examine the many technical changes in the field. After a basic overview of cryptography and what it means today, this indispensable resource covers such topics as block ciphers, block modes, hash functions, encryption modes, message authentication codes, implementation issues, negotiation protocols, and more. Helpful examples and hands-on exercises enhance your understanding of the multi-faceted field of cryptography.
Table of Contents (9 chapters)

Chapter 13
Introduction to Cryptographic Protocols

Cryptographic protocols consist of an exchange of messages between participants. We've already seen a simple cryptographic protocol in Chapter 11.

Creating secure protocols is challenging. The main problem is that as a designer or implementer, you are not in control. Up to now we have been designing a system, and have had control over the behavior of various parts. Once you start communicating with other parties, you have no control over their behavior. The other party has a different set of interests than you do, and he could deviate from the rules to try to get an advantage. When working on protocols, you must assume that you are dealing with the enemy.

13.1 Roles

Protocols are typically described as being executed by Alice and Bob, or between a customer and a merchant. Names like “Alice,” “Bob,” “customer,” and “merchant” are not really meant to identify a particular individual...