Identity-Based Cryptography - Security for Wireless Sensor Networks Using Identity-Based Cryptography - page 57

Chapter 4
Identity-Based
Cryptography
In This Chapter
• Introduction to public key cryptography
• Identity-basedcryptography
• Review of identity-based authentication and encryption schemes
• Key escrow problem and threshold signature schemes
4.1 Introduction
Throughout the history of human civilization, the need for secure communication has
been one of the top priorities. The word cryptography comes from two Greek words
( kryptos = hidden ) and ( graphein = writing ). In fact, the need to send concealed mes-
sages dates back to the Stone Age, when human beings started living in groups. As soon
as these groups evolved, the level of trust among them deteriorated. Hence, the need to
send messages among the allied groups/tribes in a hidden manner increased. As early
as 1900 b.c., the Greeks wrapped a tape on a stick and wrote a message on the tape in a
sequential manner. Upon unwinding the tape from the stick and reading the message,
the text would be meaningless. To decipher the message, the receiver needed a stick
with the same diameter as that of the sender. However, breaking this code was simply
a matter of trying sticks with different diameters.
Julius Caesar invented one of the earliest cryptographic systems to send encrypted
messages to his generals. It is popularly known as the Caesar shift cipher, wherein each
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