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WAR OF THE CODES

In intelligence battles, the side that has the best cryptographers

usually comes off better. Code-making and codebreaking achieved

a new importance in the semi-continuous warfare between the great

powers of Europe from the sixteenth century onward. Each side

attempted to crack the codes of adversaries and allies alike, while

developing what they hoped would be impenetrable codes of their own.

The sixteenth and seventeenth centuries witnessed

a steady growth in international post, and the

correspondence of prominent individuals, embassies,

and other state services were of great interest to

national spy chiefs. France was the first country to

develop a way to spy on letters with the formation

of the cabinet noir, or black chamber. The function of

the black chamber was to intercept, open, and decode

a letter, then send it on to its destination such that the

recipient would never find out that it had been tampered

with. Other nations soon followed the French lead with

black chambers of their own.

ENDING THE SIEGE

France’s black chamber was run by the brilliant

cryptographer-mathematician Antoine Rossignol. He

established his reputation in 1626 during the Catholic

siege of the Huguenot (French Protestant) city of

Réalmont, when he broke a coded letter intercepted from

the defenders, pleading for ammunition to replace their

nearly exhausted supplies. The letter was then read out

to the defenders. Realizing that help would not arrive

and their plight was known to their Catholic besiegers,

the defenders promptly surrendered.

Rossignol did much to improve the quality of

the then-lax code-making practices of the French

administration. He and his son Bonaventure developed

the Grande Chiffre (Great Cipher) especially for Louis XIV.

At the time, the system seemed impossible to break.

When the cipher key was lost in the mid-eighteenth

century, it remained unbroken until the 1890s, when

another brilliant French codebreaker, Étienne Bazeries,

cracked it after three years of work.

BRITISH SUCCESSES

If France had taken the lead in advanced

cryptography, then its main rival, England, was

not far behind. John Wallis, who had started

his career during the English Civil War, happily

and productively worked for kings Charles II

and William III following the restoration

of the monarchy. On his death in 1703, Wallis

handed over to his grandson William Blencoe,

succeeded in turn by the able Edward Willes

and his family. By the middle of the

eighteenth century, France was losing

the war of the codes, its standard ciphers

regularly broken by cryptographers in

Britain, Russia,and Austria.

CHAPTER 2 | 1600s–1800s

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