[share_ebook] Cryptology Unlocked by Reinhard Wobst 2007

作者: Reinhard Wobst

日期: 2001

ISBN: 978-0-470-06064-3

页数: 553

语言: English

出版社: John Wiley & Sons

标签: 黑客安全

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图书介绍

Author: Reinhard Wobst
Publisher: John Wiley & Sons
Publish Date: 2001
Pages: 553

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
http://www.wileyeurope.com/go/cryptology
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