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THE RISE OF ISLAM

25

CODE MASTER

After its military conquests,

the Arab world witnessed an

extraordinary blossoming in

both the cultural and scientific

spheres. Among the foremost of

the new Arab scholars was the

polymath Yaqub ibn Ishaq al-

Kindi (800–873ce), who was also

a master of making and breaking

codes. Al-Kindi’s key contribution

to the study of cryptography

was the development of the

frequency principle, namely, that

in every language some letters

are used more than others. In

English, for example, the most

common letter is E, which is

likely to be used 57 more times

than the least common letter Q.

This knowledge enabled

cryptographers to locate key

letters and open up the relatively

simple substitution ciphers of the

type used by Julius Caesar.

Left: Al-Kindi worked at the House of

Wisdom, a renowned seat of learning in

Baghdad at which many Islamic scholars

and scientists pursued their studies.

Below: Frequency tables such as

this one for English can be used

to crack substitution codes. The

codes need to be long enough to

identify the common letters,

such as E, T, and A in English.

a b c d e f g h i j k l m n o p q r s t u v w x y z

0.14

0.12

0.1

0.08

0.06

0.04

0.02

0