Cryptography Reference
In-Depth Information
seem like a “toy” example, but it illustrates the essential
features of cryptography. It is worth remarking that the
first example shows how even a child can create ciphers,
at a cost of making as many flips of a fair coin as he has
bits of information to conceal, that cannot be “broken” by
even national cryptologic services with arbitrary comput-
ing power—disabusing the lay notion that the unachieved
goal of cryptography is to devise a cipher that cannot
be broken.
crypTology in privaTe and
commercial life
At the very end of the 20th century, a revolution occurred
in the way private citizens and businesses made use of
and were dependent on pure information, i.e., informa-
tion with no meaningful physical embodiment. This was
sparked by two technical developments: an almost univer-
sal access to affordable real-time global communications,
and the practical capability to acquire, process, store, and
disseminate virtually unlimited amounts of information.
Electronic banking, personal computers, the Internet and
associated e-commerce, and “smart” cards were some of
the more obvious instances where this revolution affected
every aspect of private and commercial life.
To appreciate how this involved cryptology, con-
trast what is involved when a customer makes a noncash
purchase in person with what is involved in a similar
transaction in e-commerce. For a direct purchase, the
merchant routinely asks for some photo identification,
usually a driver's license, to verify the customer's identity.
Neither party is ordinarily concerned with secrecy; both
are vitally concerned with other aspects of information
integrity. Next, consider an analogous transaction over the
