Preface
This book is intended as a reference for professional cryptographers, presenting the
techniques and algorithms of greatest interest to the current practitioner, along with the sup-
portingmotivationand background material. It also provides a comprehensive source from
which to learn cryptography, serving both students and instructors. In addition, the rigor-
ous treatment, breadth, and extensive bibliographic material should make it an important
reference for research professionals.
Our goal was to assimilate the existing cryptographic knowledge of industrial interest
into one consistent, self-contained volume accessible to engineers in practice, to computer
scientists and mathematicians in academia, and to motivated non-specialists with a strong
desire to learn cryptography. Such a task is beyond the scope of each of the following: re-
search papers, which by nature focus on narrow topics using very specialized (and often
non-standard) terminology; survey papers, which typically address, at most, a small num-
ber of major topics at a high level; and (regretably also) most books, due to the fact that
many book authors lack either practical experience or familiarity with the research litera-
ture or both. Our intent was to provide a detailed presentation of those areas of cryptogra-
phy which we have found to be of greatest practical utilityin our own industrialexperience,
while maintaining a sufficiently formal approach to be suitable both as a trustworthyrefer-
ence for those whose primary interest is further research, and to provide a solid foundation
for students and others first learning the subject.
Throughout each chapter, we emphasize the relationship between various aspects of
cryptography. Background sections commence most chapters, providing a framework and
perspective for the techniques which follow. Computer source code (e.g. C code) for algo-
rithms has been intentionallyomitted, in favor of algorithmsspecified in sufficient detail to
allow direct implementation withoutconsultingsecondary references. We believe this style
of presentation allows a better understanding of how algorithmsactually work, while at the
same time avoiding low-level implementation-specific constructs (which some readers will
invariably be unfamiliar with) of various currently-popular programming languages.
The presentation also strongly delineates what has been established as fact (by math-
ematical arguments) from what is simply current conjecture. To avoid obscuring the very
applied nature of the subject, rigorousproofs ofcorrectness are inmost cases omitted;how-
ever, references given in the Notes section at the end of each chapter indicate the original
or recommended sources for these results. The trailing Notes sections also provide infor-
mation (quite detailed in places) on various additionaltechniques not addressed in the main
text, and provide a survey of research activities and theoretical results; references again in-
dicate where readers may pursue particular aspects in greater depth. Needless to say, many
results, and indeed some entire research areas, have been given far less attention than they
warrant, or have been omitted entirely due to lack of space; we apologize in advance for
such major omissions, and hope that the most significant of these are brought to our atten-
tion.
To provide an integrated treatment of cryptography spanning foundational motivation
through concrete implementation, it is useful to consider a hierarchy of thought ranging
from conceptual ideas and end-user services, down to the tools necessary to complete ac-
tual implementations. Table 1 depicts the hierarchical structure around which this book is
organized. Corresponding to this, Figure 1 illustrates how these hierarchical levels map
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