Customer Reviews

Cryptography Demystified

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If you can make sense of this then you'll be able to make sense of the rest of the book (From Module 4):

Prob[p(t)=1lc(t)={Prob[c(t)=1lp(t)=1]Prob[p(t)=1]}/{Prob[c(t)=1]}
Now,
Prob[c(t)=1lp(t)=1]=Prob[k(t)=0]
and
Prob[c(t)=1]=Prob[p(t)=1]Prob[k(t)=0]+Prob[p(t)=0]Prob[k(t)=1]
therefore,
Prob[p(t)=1lc(t)=1]={prob[k(t)=0]Prob[p(t)=1]}/{Prob[p(t)=1]Prob[k(t)=0}+Prob[p(t)=0]Prob[k(t)=1]}

This book is slanted towards more theory and math than others that deal in practicality, for instance "Cryptography for Dummies". But if you have a solid foundation in mathematics and have the temporal ability to "quantinize" then this is a fantastic book. I would speculate this book is meant for graduate comp. sci/eng coursework as it is broken down into 35 Modules with problem solving exercises at the end of each. At any rate, good luck!

John Hershey's latest book is a skillful blend of information describing, illustrating, and proving the basic foundations and principles of modern cryptography. It combines the experience of a professional cryptographer and researcher with the clear writing and insightful examples of an excellent teacher.

The book focuses on the major components of a cryptographic system and presents in a quite readable way, some very important and subtle concepts that should be followed when designing and implementing a system. He also presents some non-obvious pitfalls that must absolutely be avoided. For those who are able and willing to work through the mathematics, a solid foundation is presented for symmetric cryptography (e.g. DES), public key cryptography (e.g. RSA), and cryptographic key management. However, a mathematical background is not necessary to derive a great deal of benefit from Cryptography Demystified. Even eliminating all of the mathematics, a reader who carefully studies the various concepts and ideas presented will gain a great deal of understanding of which properties make a good cryptographic system and which do not, along with the reasons why.

This book is not a history of cryptography such as David Kahn's The Codebreakers nor an encyclopedia such as Bruce Schneier's massive compendium Applied Cryptography . It is a carefully crafted work by a brilliant and creative person as demonstrated by his over 70 patents, another 50 patents pending, and extensive list of publications. Many of these patents and publications are in the field of cryptography and security. Cryptography Demystified guides the reader through all of the major elements of a cryptographic system with illustrations from the Caesar cipher through the theoretical principles of quantum cryptography in the Channel Cryptography section. Sets of exercises (with answers at the back) are included at the end of each chapter for the more serious readers to test their understanding.

As president of an information security consulting company and someone who started 35 years ago as a mathematician working on U.S. Government cryptography , I wish I had such a book then and find I can learn from it now.

I took the author's graduate course on cryptography while this book was still in draft form. The material addresses the difficult and essential foundations of cryptography in a way that is accessible to people with a wide variety of backgrounds. Anyone interested in cryptography, from the computer enthusiast to the number theorist will enjoy and gain insight from this book.

Almost twenty years ago, I was a graduate student of John Hershey's. At that time, and in the classroom (and, oh by the way, the class began at 7:30 AM), John was a magnificent instructor, with an incredibly agile mind, who was able to make even the most bleary-eyed of us understand the basic concepts and complexities of cryptography. Reading this new book for the first time not only brought back the lessons that I'd learned in the classroom, but provided me with new insight and understanding of this subject that has become increasingly important with the ubiquitousness of data communications.

Following the model of Nobel Laureate Richard Feynmann whose lectures and class notes provide a meaningful glance into the world of theoretical physics, John Hershey's lectures have been assembled and compiled for this book. "Demystifying Cryptography" provides a clear path for interested students to follow from the most basic introductory concepts to the highly complex topics covered in later chapters. Throughout the book, the explanations are both clear and insightful. The exercises provided at the end of each chapter provide even the most casual of reader with the opportunity to practice and master the concept addressed within the text.

Understanding cryptography is a challenging task, even to the most dedicated and gifted student. But this book provides readers with the tools to accomplish that task, and it does so with clarity and simplicity. "Demystifying Crytography" is an excellent source of useful information. It's also a terrific intellectual workout. Like the subject matter itself, the material is challenging, but its mastery is both fun and rewarding.

This book was used in a course I took taught by the author, Dr. John Hershey. I have read and own several books in this category, am working to obtain two advanced degrees in the field of computer security, and feel that I have enough information to write an objective review. It is an excellent introduction book to the general area of cryptography, but suffers from several shortcomings.

If you do not know much about what cryptography and encryption are, this book should provide a decent introduction. The book provides the mathematical concepts needed to understand the chapters, but I felt it did not cover enough detail or provide enough examples to let me feel I had a solid understanding of everything.

There are three aspects to cryptography: authentication, integrity, and verification. This book only discusses integrity issues, i.e. encryption. DES, RSA, and Diffie-Hellman are discussed, but a detailed covering of AES is noticibly absent. It covers integrity rather well, breaking down the different methods of using block encryption into separate chapters. In other words, DES operation in electronic codebook, output feedback, and cipher feedback modes are three different chapters. This is something that isn't usually done and is a rather nice touch. It makes it much easier to learn the advantages and disadvantages for each mode of operation.

In terms of total mathematical theory, Hershey's book does not contain much theory. If you want theory, I recommend you find William Stallings book titled "Cryptography and Network Security: Principles and Practice." Also, Hershey's book does not contain code to let you start programming a security system. If you want applications, I recommend you find Bruce Schneier's book titled "Applied Cryptography: Protocols, Algorithms, and Source Code in C." Those books are for advanced readers, however, and may be difficult to understand if you don't know the area.

Overall, it is a good read. I recommend it more for IT people than computer scientists or engineers simply because it touches upon the topic, instead of being very detailed. Look at the editorial review section criteria for who should read the book, it is right for the most part.

If you are looking to expand your mind, think about learning Cryptography. It is an excellent discipline to help you think in new ways. If you decide you want to learn Cryptography, this is the book for you. The book is written in modules, making it easy to digest. The book is equally suitable for a formal classroom or self-study environment. Using the book for self study is enhanced by the modular format, superb clarity of the teaching, the well-explained answers to the problems, and the appropriately injected humor. People that need to learn Cryptography will undoubtedly have this book on their shelf, whether they are an expert or beginner. I would like to speak to the people that don't need to learn Cryptography - this book is for you too, as you will enjoy learning the thought processes of Cryptography that will enhance your creativity in any field. This book is a gift.

Cryptography Demystified reflects refined and fundamental thinking in cryptography. Dr. Hershey's style is enjoyable without compromising subtle points in the field. The book is an excellent reference book or college textbook for teaching Symmetric and Public Key Crypotography. Also, Dr. Hershey's treatment of Channel-based Cryptography is quite amusing and a source for research topics.

As an electrical engineer new to the subjects of cryptography and number theory, I found this book provided a solid introduction to the fundamentals of cryptography. John Hershey conveys the important subtleties and pitfalls essential to evaluating cryptographic systems. He lays out the basic paradigm and takes you step by step through the algorithms and mathematics in a straight forward easy to follow manner. By the end you will have acquired the tools necessary to understand more advanced cryptographic schemes. Overall, I would highly recommend this book to others interested in gaining knowledge about the inner workings behind today's cryptographic systems.

John Hershey has an almost unbelievable passion for cryptography which is exceeded only by his knowledge of the subject. His presentation of the material is kept entertaining with witty anecdotes that are beautifully relevant, but deviation from content never occurs. I highly recommend Dr. Hershey's book to anyone who wants a good introduction to both the theory underlying and the application of cryptography.

John Hershey, a creative luminary at General Electric, has out-done himself in this excellent work. The material is well-organized and clearly explained. The execises are fun and insightful. This book sparks one's interest in a topic that can be dull and dreary to many people. This is a must-read for anyone in the field.

Well done!