BKDECSEC.RVW   20020520

"Decrypted Secrets", F. L. Bauer, 2002, 3-540-42674-4, U$44.95
%A   F. L. Bauer
%C   175 Fifth Ave., New York, NY   10010
%D   2002
%G   3-540-42674-4
%I   Springer-Verlag
%O   U$44.95 212-460-1500 800-777-4643 rjohnson@springer-ny.com
%O  http://www.amazon.com/exec/obidos/ASIN/3540426744/robsladesinterne
%P   474 p.
%T   "Decrypted Secrets: Methods and Maxims of Cryptology, 3rd Ed."

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 than it is to demonstrate a sufficient mastery of mathematics to
enable you 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 are introduced in chapter ten.  The relative
security of encryption is introduced in chapter eleven, leading to
part two.  However, Chapter eleven 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.  This third edition is essentially and structurally
unchanged from its predecessors, although it has been updated to
reflect the latest algorithms and technologies.  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, 2002   BKDECSEC.RVW   20020520