Fair Exchange: Theory and Practice of Digital Belongings
by Carlos Molina-Jimenez, Dann Toliver, Hazem Danny Nakib, and Jon Crowcroft
World Scientific Publishing 2024.
ISBN ISBN: 978-1-80061-516-8 (hardcover), ISBN: 978-1-80061-518-2 (ebook)
292 pages + xxiii
Reviewed by Sven Dietrich 06/04/2024
We are talking about fair exchange protocols here. The world of exchanging information or digital goods in a fair way in our digital economy can get tricky and test the trust relationships of the concerned parties. It can lead to sometimes even going as far as two parties mutually, or in turns writing or adding one letter of a contract at a time.
The author team at the University of Cambridge, Carlos Molina-Jimenez, Dann Toliver, Hazem Danny Nakib, and Jon Crowcroft, have set out to create a book that introduces the reader to the world of fair exchange, from theory to practice. And they succeeded in this task. This almost 300-page book is divided into three parts and twenty chapters. Throughout the book, you will find both black-and-white as well as color illustrations and figures, all of which are listed in a List of Figures and List of Tables. A roadmap in the beginning of the book helps the reader understand the flow of the book. A set of references, a glossary, and an index round off the book. Part 1 discusses "A Framework for Fair Exchange" and contains 7 chapters. This is a thorough introduction to the field of fair exchange. The first chapter "Fair Exchange Protocols" goes into the basics, such as definitions, the history, trust assumptions, and other properties one may encounter in this context. The second chapter "Categories of Items" describes the items in the context of fair exchange, such as copyable items, unique items, and digitally inaccessible items, and sets the stage further for grasping this world. The third chapter "Operations of Fair Exchange" shows what the basic operations are, from the initial handshake to the deposit, verify, and synchronize, up to the final release or restore stages. Next, the fourth chapter "Environments for Operation," as well as the fifth chapter "A Diagram Language for Fair Exchange" set up the reader for describing the fair exchange protocols better. As a logical next chapter, "The Fundamental Limits of Fair Exchange" shows how the pieces are put together in understanding the various stages shown in Chapter 3 more thoroughly. The last chapter on "Attestables" describes an interface for independent computation. Part 2, in turn, is on "Protocols Old and New," and also comprises 7 chapters. Armed with the building blocks from Part 1, the reader can now analyze existing protocols, and even create new ones, partially helped by the "attestable" concept introduced in chapter 7. The categorization of protocols divides the space for a better understanding of fair exchange protocols, and goes on to further critique protocols, from escrow-based to optimistic ones, from gradual-release to attestable fair exchange protocols. This leads to a wrap-up of Part 2, Fair Exchange Without Disputes and a family of such protocols. Part 3 "Real World Fair Exchange" has a focus on the real world, keeping in line with the title "theory and practice." Over 6 chapters, the authors connect the topic of fair exchange to real-world scenarios. In "Risk Analysis," the authors discusses topics such as false positives, risk quantification, as well as the impact of faulty environments. In "Legal Considerations," the reader will find topics such as records and evidence, the types of disputes that may (or not) be eliminated by certain fair exchange protocols, and a sample set of protocol phases. "Operational Concerns" and "Commercial Analysis and Use Cases" delve deeper into making it work, such as exchanges of signatures and legal contracts, as well as completing missing information from such a fair exchange protocol. Last but not least, the connection is made to timely topics along the exchange of digital goods, such as smart contracts, secure multiparty computation, and zero-knowledge information exchange. Overall the book is aimed at researchers, industry practitioners in technology, e-commerce, and online marketplaces, and postgraduate students that seek in-depth information about fair exchange protocols, from the tried and true to the latest and greatest ideas. The authors did a fine job at assembling relevant topics of this important aspect of our online presence. I met one of the authors at a conference where smart contracts and blockchain topics were being presented: it is a an excellent connection for this book, as mentioned in Part 3. I very much enjoyed reading this book, and the book will find its place on my bookshelf for any needed reference on this fascinating topic.