Customer Reviews

Practical Cryptography

5 star:		(8)
4 star:		(3)
3 star:		(4)
2 star:		(0)
1 star:		(1)

 

 

For those of you (including myself) who were expecting an updated version of the Applied Cryptography, this book is NOT it. Based on the pre-publication blurbs here and there, I thought it may be a simple how-to book without too much theory. The book didn't turn out to be that sort of thing either.

This book is, sort of an executive summary of Applied Cryptography (AC), with some updates. It touches upon the insights that Scheneier mentioned in Secret and Lies (like crypto is the easy part and that won't solve security). It mentions some newer material, notably AES related stuff. The description is, in effect, a simplified version of AC. Also, it doesn't try to cover everything, and yes, some explanations about the practical applications are stressed slightly more than in AC.

So if you want to be practical, just go over the essential and latest stuff, this is a good book to read. But I must say that it's not as fun to read as AC. Not as many jokes, and absolutely no crazy stuff (like bio-computing and the significance of dark matters). Oh well, maybe that's what being practical means... But it doesn't give you the feeling of throughness that AC gave. Maybe this comes from my reading AC too much in detail (I actually translated the whole book into Japanese), but I think it is inherent in the book itself. In trying to cover as much ground as possible, the book hurries a lot.

So if you are in a hurry to cover just enough important stuff, get this book. And if you need some explanation on the newer stuff, get this. But I also recommend getting AC as well.

I've read a large number of cryptography books. Very few of them come down to brass tacks. They give you a description of a few algorithms, their strengths and weaknesses, and leave it at that. Either that, or they describe in lovingly complex detail the implementation of a particular protocol, one usually so fraught with options and details that you wonder how, at the end of it, that anybody writes a conforming implementation.

Practical Cryptography does neither of these things. It presents algorithm classes, why they exist, and what the best known algorithms are in each class. It explains how the various strengths and weaknesses of algorithms in each class combine to make a cryptosystem weaker or stronger. Then it goes on to show you how to use that information to build working cryptosystems.

This book is NOT a careful discussion of the implementation details or plusses and minuses of particular algorithms. They give detailed implementation instructions and advice for some algorithms (such as RSA or Diffie-Hellman) that tend to end up being misunderstood or implemented poorly, but the main focus of the book is about putting all the information together to build a real system. This is something that I feel is sorely lacking in the field of cryptography as it stands in 2005 (when I last updated this review).

The book does have a flaw. The authors present several algorithms and techniques that they recently invented and are not 'tried-and-true'. They present good arguments as to why they're secure. But the only real test of such things is lots of peer review and real-world testing. And, since they're new, they haven't been tested in that way.

People have complained about the book's seeming schizophrenia. On one hand, the authors are trying to show you how to build a secure cryptosystem. On the other, they're telling you how hopeless a task it is to build one that has no vulnerabilities, even if you're an expert in such things.

This can be annoying, but I more find it refreshing. Writing a secure cryptosystem is very hard. People should be aware that it is hard, and they are likely to make mistakes. It isn't something that should be attempted lightly. The current state of computer security is depressingly abysmal. People should be encouraged, as much as possible, to not contribute to the problem.

I'm not following my own advice, and I am building a new cryptosystem. I have found this book a more valuable resource than any other book on cryptography that I have yet read. Even if you aren't building your own cryptosystem, I think you will find the insights this book has into complexity and design to be useful tools in evaluating other cryptosystems.

As one other reader pointed out this book can be called Applied Cryptography Light. It is true, it gives you more theory and very little math. I did not like this book by itself since I was interested in actual implementation and i wanted to see full algorithms and math. I did end up buying Applied Cryptography and those 2 books combined provide an excellent reference. I was not able to give more than 3 stars since I did not feel i got any knowledge out of this book to be able to apply it in real life except reading: "Cryptography is hard, you might need to hire an expert..." while I want to become an expert myself one day!

From the very first pages, authors emphasize the need for public algorithms and peer review. Yet, the book is full of suggestions that appear first time in the book. They even take time to give fancy names to their new proposals. It is typical to see things like "While writing this chaper we came up with this new random number generator...". Well, the authors could have used some of public scrutiny they are so fond of.

The authors are extremely biased against algorithms designed by others. For example, they bend over backwards to blow some generic weaknesses of AES out of proportions. They even add a scary story of a bored PhD student offhandedly breaking AES. I think this not only unfair but also a bit unethical to direct generic critisism to a design and then pretent it does not apply to their own.

They must be really pissed off when their own algorithm was beaten by AES in the NIST competition.

The book is useful if all you want is a light reading about security and you can manage to read it with a grain of salt.

Well, I can't really recommend the book. It's readable enough,
but I can't figure out their target audience. Only someone actually
implementing a cryptographic system would get anything out of
this book. At the end of the book, they warn you that a good
implementation is so hard that you really should hire an
expert to do it. They also say "The world is full of of bad
security systems designed by people who have read Applied
Cryptography. Practical Cryptography is likely to have the
same effect."

They say they wrote the book as an introduction to the state
of the art ("[people] .. must learn it somewhere, and we didn't
know of any other suitable books.") Given that no one but a
programmer or mathematician would get through half the book,
it's unlikely to reach a general audience, or even the managers
who really need their advice.

The content level of the book is very uneven as well, with
general, strategic advice mixed with algorithm discussions. Yet
there's almost no nuts and bolts programming advice. They just
point you off to other sources for all of that.

They have these little "So what should I do?" sections at the
end of most chapters, but they are pretty cynical. The most
common advice amounts to "there's no way to know without analyzing
your requirements." The other comments are along the lines of
"the software industry is a mess", "the standards process is a mess",
"the patent process is a mess", "(technique X) hasn't been around
long enough to be analyzed much, is a patent minefield, or has been
broken, or nearly broken. Don't use it." And finally, that security
depends on the weakest link, which generally won't be the
cryptography anyway. (Don't even try to do this at home!) This
may all be true, but it's not really helpful.

I don't know if you could implement a complete system from their
description of which techniques are reasonably good. If you
trusted their implementation advice, should you also trust their
overall advice, which is to leave this to the experts?

The whole thing leaves me with the impression that they are pretty
bitter about the whole field. They want people to do better on
security, but they have no expectation that they will. They want
to be listened to (and hired), but don't expect that either. The
book is mostly to say "see how complicated this is (you idiots!)?"

Two of the leading world cryptographers take their time to show engineers of all kinds, not just programmers, how the security is to be implemented.

To quote: "one of the reasons for writing this book: to get other people to understand the insidious nature of security, and how important is to do it right."

The whole point of the book is to show how would the authors have built an encryption system if everything's to be done right. This means secure communication channel, key negotiation, random number generation and public key encryption. Basically what you have in this book is a blueprint for the best possible crypto system.

The authors describe a few cryptographic primitives, like block ciphers and hash functions, but not a whole lot and nothing in details. The authors just pick one of each (explaining exactly why the one they picked is the best) and stick with it throughout the book.

The book has surprisingly little math, if any. No details of any existing protocol in particular.

A lot of (literally dozens) attacks described, at any point, on any part, and for each a cure is proposed or "no cure possible" conclusion is made. Pretty informative.

Lots of advises, some more technical, some more philosophical. Lots of auxiliary info, like patents on crypto, dancing pigs :), implementation notes etc. Some chapters are about a dozen pages long. A touch, but it makes you think.

Oh, and it describes Mr. Schneier's new Yarrow random generator, and what's more - a shiny new extension to it called Fortuna. Fascinating stuff if you ask me.

There are some minor downsides too.

First, the pseudocode which is used for describing algorithms is strikingly bad. Dear authors of computer books, even if you don't want to take any language's side, please make your code readable for programmers.

Second, a few times the book goes like this: "there is that thingy, it's green and it does things". What ? I think if you even mention things, making a consistent view of what it is at least would be nice. To be specific, the book mentions but never even tries to explain: UMAC, OCB, CCM. There is a few more but I wouldn't mind omitting details on those as they are specifically marked as "stay clear off". I could have googled for them for sure, but what is the point of the book then ?

Third, some of the advises, especially on programming side don't stand. I found the most useful advises the ones that begin with "Niels once had..." and "We found useful...", i.e. the advises from the field. Some other advises are too general. In the very same time the authors say something like "we (the world) don't have a clue how to write secure software". I fully agree, but why trying to squeeze in a small book thus useless advises ? Like for instance, first they say "wipe any information as soon as you no longer need it" and then "assertion failures should always lead to an abort of a program". Cleanup, huh ? Shall we just say that writing quality software takes no less books than designing proper crypto ?

So, the book gets 5 out of 5, because it (1) delivers exactly what it advertises (2) provides an good coverage on the topic and (3) the authors are but the best cryptographers there are.

Recommended for anyone.

This book really does explain the practical side of cryptography and writing cryptographic software.

The authors take the readers with them as they design a secure communication system using existing algorithms and standards. You look over the shoulders of two experts in the field as they make decisions (e.g. AES vs. Serpent vs. Twofish) and explain them (e.g. AES is the IBM of algorithms, Serpent is the most secure, and Twofish is fast like AES but without the vulnerabilities).

There is an entire chapter devoted to "Implementation Issues" which includes some of the best information on software design I have ever read. In addition to the cryptography related information, the authors point out some flaws in traditional software development methodology. In fact, this book should be required reading for every computer science student and every practicing software engineer.

If you have had trouble understanding cryptography and cryptographic algorithms in the past, this book will fill in the gaps. The book very well written, which is a rarity in the field of cryptography. If you are a crypto-phile, you can actually read this book for entertainment.

If you liked Applied Cryptography, but were turned off by all the math, get this book.

It is Applied Cryptography Light.

Not that this is such an easy read, but a much easier, updated and practical read than Applied Cryptography.

This can be an annoying book for a serious developer, but I do know Writing a secure cryptosystem is very hard. People should be aware that it is hard, and they are likely to make mistakes. It isn't something that should be attempted lightly. If you are doing some actual work, it's not a good one. The book does not cover sufficient mathematic knowledge, and the edit is bit horrible as well. The authors chose to support their own algorithm shedding less light on AES and even RSA. That really made me stop reading this book.
The author's other book "Applied Cryptography" is still my favorite.

If you want an honest and extremely realistic analysis of security and encryption in general, this is the book for you. The authors are "dead-on" in their analysis of security as a process instead of just a system for cryptography. They especially "hit-the-mark" in their analysis of the sad state of affairs in Bio-Metrics and PKI (Public Key Infrastructure). This is not a balanced "middle-of-the-road" analysis. Instead, it is an opinionated view of security and cryptography solutions, implementations, and idealizations. The author's opinions are welcome and correct. They have the experience and they make more sense than most. (Not to mention that they take a very sensible approach the topics).