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 7
The Secure Channel

Finally we come to the first of the real-world problems we will solve. The secure channel is probably the most common of all practical problems.

7.1 Properties of a Secure Channel

Informally, we can define the problem as creating a secure connection between Alice and Bob. We'll have to formalize this a bit before it becomes clear what we are talking about.

7.1.1 Roles

First, most connections are bi-directional. Alice sends messages to Bob, and Bob sends messages to Alice. You don't want to confuse the two streams of messages, so there must be some kind of asymmetry in the protocol. In real systems, maybe one party is the client and the other the server, or maybe it is easier to speak of the initiator (the party that initiated the secure connection) and the responder. It doesn't matter how you do it, but you have to assign the Alice and Bob roles to the two parties in question in such a way that each of them knows who is playing which role...