[3504] in cryptography@c2.net mail archive
[ISN] REVIEW: "Decrypted Secrets"
daemon@ATHENA.MIT.EDU (Jay D. Dyson)
Sat Oct 17 11:38:39 1998
Date: Fri, 16 Oct 1998 16:08:49 -0700 (PDT)
From: "Jay D. Dyson" <jdyson@techreports.jpl.nasa.gov>
To: Cryptography List <cryptography@c2.net>
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Courtesy of InfoSec News. Thought some folks here would like to see this.
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Forwarded From: darek milewski <darekm@cmeasures.com>
BKDECSEC.RVW 980804
"Decrypted Secrets", F. L. Bauer, 1997, 3-540-60418-9, U$39.95
%A F. L. Bauer
%C 175 Fifth Ave., New York, NY 10010
%D 1997
%G 3-540-60418-9
%I Springer-Verlag
%O U$39.95 212-460-1500 800-777-4643
%P 447 p.
%T "Decrypted Secrets: Methods and Maxims of Cryptology"
Cryptology is the study of the technologies of taking plain, readable
text, turning it into an incomprehensible mishmash, and then recovering
the initial information. There are two sides to this study. Cryptography
is the part that lets you garble something, and then recover it if you
have the key. Cryptanalysis is usually seen as the "dark side" of the
operation, because it is the attempt to get at the original meaning when
you *don't* have the key. Most current and popular works on cryptology
actually only speak about cryptography. For one thing, nobody wants to
get into trouble by telling people how to break encryption. However, it
is also much easier to blithely talk about key lengths and algorithms and
pretend to know what you are doing if you don't have to understand enough
math to try to figure out how to go about cracking a particular cipher.
Bauer examines both sides, which is an important plus. If you need to
decide how strong an encryption algorithm or system is, it is important to
know how difficult it might be to break it.
Chapter one looks at Steganography, the science of hiding in plain sight,
or concealing the fact that a message exists at all. In this he first
demonstrates a wide ranging historical background which is quite
fascinating in its own right. Basic encryption concepts are introduced by
the same historical background, but move on to a very dense mathematical
discussion of cryptographic characteristics in chapter two. Encryption
functions are started in chapter three, and it is delightful to have
examples other than Julius Caesar's substitution code. Polygraphic
substitutions are in chapter four and the math for advanced substitutions
is in chapter five. Chapter six introduces transpositions. Families of
alphabets, and rotor encryptors such as ENIGMA, are reviewed in chapter
seven. Keys are discussed in chapter eight, ending with a brief look at
key management. Chapter nine covers the combination of methods resulting
in systems such as DES (Data Encryption Standard). The basics of public
key encryption is introduced in chapter ten. The relative security of
encryption is introduced in chapter eleven, leading to part two. However,
it also ends with a discussion of cryptology and human rights,
concentrating mainly, although not exclusively, on the US public policy
debates.
Part two examines the limits of functions used in cryptography, and thus
the points of attack on encryption systems. Chapter twelve calculates
complexity, and thus the size of brute force attacks. Known plaintext
attacks are the basis of chapters thirteen to fifteen, looking first at
general patterns, then at probable words, and finally at frequencies.
Frequency leads to a discussion of invariance in chapter sixteen. Chapter
seventeen follows with a look at key periodicity. Alignment of alphabets
is covered in chapter eighteen. Of course, cryptographic users sometimes
make mistakes, and chapter nineteen reviews the different errors and
various ways to take advantage of them. Chapter twenty one looks at
anagrams as an effective attack on transposition ciphers. The concluding
chapter muses on the relative effectiveness of attacks and of
cryptanalysis overall.
Those seriously interested in cryptology will really need to be serious:
brush up on your number theory if you want to use this book for anything.
On the other hand, Bauer's history and vignettes from the story of codes
and the codebreakers are interesting, amusing, and accessible to anyone.
copyright Robert M. Slade, 1998 BKDECSEC.RVW 980804
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