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 14
Key Negotiation

Finally, we are ready to tackle the key negotiation protocol. The purpose of this protocol is to derive a shared key that can then be used for the secure channel we defined in Chapter 7.

Complete protocols get quite complicated, and it can be confusing to present the final protocol all at once. Instead, we will present a sequence of protocols, each of which adds a bit more functionality. Keep in mind that the intermediate protocols are not fully functional, and will have various weaknesses.

There are different methods for designing key negotiation protocol, some with supporting proofs of security and some without. We designed our protocol from the ground up—not only because it leads to a cleaner explanation, but also because it allows us to highlight nuances and challenges at each stage of the protocol's design.

14.1 The Setting

There are two parties in the protocol: Alice and Bob. Alice and Bob want to communicate securely. They will first conduct...