Cryptology Unlocked by Reinhard Wobst 2007

Cryptology Unlocked

Author:

Reinhard Wobst

Translated by Angelika Shafir

Publisher:

Copyright ?? 2001 by Pearson Education Deutschland GmbH

Translation Copyright ?? 2007 John Wiley Sons Ltd

Pages: 553

ISBN 978-0-470-06064-3

Preface“Cryptology”—the science of secret writing—is peculiarly fascinating. Its

vocabulary alone reminds you of crime thrillers rather than of science: radio

reconnaissance, invisible ink, encrypted message exchange, ciphertext attack. . .

This fascination begins probably rather early in our lives. I once watched my

older son as he zestfully tried to decipher some secret writing in a children’s

puzzle magazine. When I was a kid I experimented with the legendary invisible

ink made of salt solution or lemon juice (which never worked, because as I

heated it up the paper would always char instead of magically revealing the

secret writing). When my dad later told me about his method for encrypting

radio traffic (Section 2.3), I was thrilled and had a dim feeling that there’s got

to be a bunch of mathematics behind it. I simply couldn’t imagine that anybody

could ever be able to read such ciphers without knowing the key. And with so

many keys around—no way anybody could try them all out!

My next encounter with cryptology happened two decades later. Long after my

math studies, I had access to a PDP11 computer and experienced for the first

time that computers can be there for people rather than the other way round. I

began to test an encryption algorithm I invented on this computer and thought

it to be bomb-proof—as always when you don’t have enough background

knowledge. Ten years later, I further developed this algorithm, studied it to the

best of my knowledge, and published it in the German UNIX Magazine. The

lively readers’ response took me by surprise.

Unfortunately, this algorithm was insecure. You will read in Section 3.7 how

it can be cracked.

In the years that followed, I dealt with cryptology over and again and increasingly

more often. Motivated by a magazine article, Mr Wehren of Addison-

Wesley Publishing asked me whether I would like to write a book on this topic.

I initially thought it was too daring. After a month of playing with the idea, I

agreed, and I haven’t been sorry. This book is an English version of the fourth

edition of that book, and I hope you enjoy reading it as much as I enjoyed

writing it. The book is intended to be fun, but it also has other goals.

Today, as we can’t imagine our everyday lives without cryptology, there is a

widening gap between modern and hard-to-understand cryptological research

on the one hand, and the general state of knowledge on the other hand. The

risks from na¨?ve use of bad encryption methods (or—more often—bad use

of good methods) mustn’t be underestimated. That’s not panic-mongering: We

first have to get to grips with the new information age. A popular, but not

superficial, discussion of this issue is necessary. This book is intended to be

easily understandable for non-mathematicians, too, and it should show how

exciting, many-facetted, and entertaining cryptology can be. Whether or not I

achieved these goals is up to you.

A lot has happened since the first edition of this book (1997). Cryptology has

left its mystery-mongering world, and modern society would be unthinkable

without it any more. While there were still only a handful of specialists who

furthered cryptanalysis actively (i.e., cracked code) in the mid-1990s, it is now

a broad field of research that produces interesting results. And while good

encryption was subject to tight restrictions, not only in the USA, at the beginning

of the 1990s, we now have an encryption standard like the AES that came

about by an international challenge, and the USA now use a Belgian algorithm

for their own security. Also, we understand much better today that encryption

is only a small part of security, and that most errors are made when implementing

algorithms. Nevertheless, cryptology has remained one of the hardest

subjects in information security to understand.

The developments won’t come to a standstill. Additions and corrections to this

book will certainly become necessary, though it is already in its fourth edition.

This is why you will find current information on the topics discussed in this

book and errors that attentive readers will have found at

ogy

So, if you find wrong or incomplete information, or if you think that one term

or the other should appear in the Glossary, please send an email to the address

given below.

I welcome every critical comment. But please don’t send me ciphertexts to

decrypt, or new ‘uncrackable’ algorithms. When you’ve read the book (and

particularly the text in txt/FAQ/memo.txt on our Web site!), you’ll understand

that those are extraordinarily cumbersome tasks, and I normally won’t have the

time or sometimes the knowledge.

Reinhard Wobst

r.wobst@gmx.de

GnuPG fingerprint:

897A 6984 9C8D FED9 305F 082E F762 909D A28C 4B16

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