Cryptography Reference
In-Depth Information
Chapter 1
Introduction to Cryptology
Society is becoming more information-driven every day. Naturally, the neces-
sity of keeping valuable information secret from unauthorized access is grow-
ing as well. Here comes the role of cryptology, the art and science of hiding
information.
Each one of us, knowingly or unknowingly, uses cryptology in our daily
lives. ATM machines, credit card transactions, prepaid recharge of mobile
phones, online banking, the digital gate-pass in o
ces for access control, copy-
right protection etc., are only a few examples where cryptology finds its ap-
plications. Modern military systems also make enormous use of cryptology
to secure tactical and strategic data links, such as in fighter plane control
systems, missile guidance, nuclear control etc.
1.1 Etymology and Some Historical Facts
Cryptography is derived from Greek κρνπτω (krypto) which means “hid-
den” and γραφω (grafo) which means “to write.” Thus, the term “cryptog-
raphy” means the art and science of making ciphers. On the other hand,
the term “cryptanalysis” means the art and science of breaking ciphers. The
subject cryptology comprises cryptography and cryptanalysis.
The oldest evidence of the subject is found in Egyptian hieroglyphs dating
back to 2000 B.C. The Jews around 500 B.C used a simple substitution cipher
called Atbash for the Hebrew alphabet. Around 400 B.C., the Spartans, the
military superpower of the then Greece, used a device called Scytale to perform
a transposition cipher for communication between two military commanders.
Roman emperor Julius Caesar (100-44 B.C.) used a simple substitution with
the normal alphabet to send secret messages to his soldiers in the battlefield.
Even the famous Indian text Kama Sutra, written some time between 4th and
6th century A.D., lists cryptography as an art men and women should know
and practice. During World War II, German military used a cryptosystem
called Enigma that was broken by Polish Mathematician Marian Rejewski.
Around that time Americans also used a system called M-209 and the Germans
used another system called Lorenz. Due to rapid advances in the field of
