История письма и чтения. Асафова Г.К. - 86 стр.

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UNIT 14

A CODE FOR SPIES AND PLOTTERS

By the late 15

century, the great cities of Europe were thriving

cosmopolitan centres. The major nations had ambassadors at each other’s courts:

the big trading companies and banks had representatives in foreign commercial

centres. Voyages of exploration were opening lucrative new trade routes. The

nations of Europe were engaged in tense games of economic rivalry and squabbles

for territory. Spies, plots and intrigue abounded.

Merchants and politicians communicated through a network of private

messengers and public couriers. These services, however, were easily intercepted.

All important, confidential documents were sent in code. By the middle of the 16

century major European courts had secretaries employed specifically to create,

break and send messages in code.

The most basic codes, in which one set of letters is substituted for another,

are known as ciphers. In the simplest of these, the normal alphabet is just replaced

by another alphabet. In the first century AD, Julius Caesar used this code to send

secret messages: by substituting all the letters of his text with letters three places

down the alphabet. But these ciphers are comparatively easy to break. Because the

substitution of letters is always the same, the code breaker can identify familiar

patterns.

By the 15

century, more complex tables of signs and symbols were being

used to represent the letters of the alphabet. Yet even these codes could be

deciphered. Some of the brightest minds of the time were engaged in perfecting an

impenetrable code. The first of these was the Florentine artist, musician, architect

and athlete, Leon Battista Alberti. He believed the answer lay in a “polyalphabetic”

cipher - in which the letters of the alphabet were represented by a series of other

alphabets that changed as message progressed.