Cryptography Reference
In-Depth Information
Chapter 6
Introduction to Public-Key Cryptography
Before we learn about the basics of public-key cryptography, let us recall that the
term
public-key cryptography
is used interchangeably with
asymmetric cryptogra-
phy
; they both denote exactly the same thing and are used synonymously.
As stated in Chap. 1, symmetric cryptography has been used for at least 4000
years. Public-key cryptography, on the other hand, is quite new. It was publicly
introduced by Whitfield Diffie, Martin Hellman and Ralph Merkle in 1976. Much
more recently, in 1997 British documents which were declassified revealed that the
researchers James Ellis, Clifford Cocks and Graham Williamson from the UK's
Government Communications Headquarters (GCHQ) discovered and realized the
principle of public-key cryptography a few years earlier, in 1972. However, it is
still being debated whether the government office fully recognized the far-reaching
consequences of public-key cryptography for commercial security applications.
In this chapter you will learn:
A brief history of public-key cryptography
The pros and cons of public-key cryptography
Some number theoretical topics that are needed for understanding public-key
algorithms, most importantly the extended Euclidean algorithm
