This book offers an introduction to cryptology the science that makes secure communications
possible and addresses its two complementary aspects: cryptography---the art of making secure
building blocks---and cryptanalysis---the art of breaking them. The text describes some of the
most important systems in detail including AES RSA group-based and lattice-based
cryptography signatures hash functions random generation and more providing detailed
underpinnings for most of them. With regard to cryptanalysis it presents a number of basic
tools such as the differential and linear methods and lattice attacks. This text based on
lecture notes from the author's many courses on the art of cryptography consists of two
interlinked parts. The first modern part explains some of the basic systems used today and
some attacks on them. However a text on cryptology would not be complete without describing
its rich and fascinating history. As such the colorfully illustrated historical part
interspersed throughout the text highlights selected inventions and episodes providing a
glimpse into the past of cryptology. The first sections of this book can be used as a textbook
for an introductory course to computer science or mathematics students. Other sections are
suitable for advanced undergraduate or graduate courses. Many exercises are included. The
emphasis is on providing reasonably complete explanation of the background for some selected
systems.
