Black Chamber

Black Chamber


The term "black chamber" has come to represent any code-breaking organization, but was originally applied to groups of code-breakers associated with the French postal service that intercepted, read, copied and decoded diplomatic mail. In the twentieth century, Americans created a black chamber to intercept and decode radio transmissions (telegraphs) rather than postal mail.

In the seventeenth century, talented individuals such as Antoine Rossignol (1600–1682) in France, and John Wallis (1616–1703) in England showed the value of code breakers in affairs of state. Their efforts encouraged European governments in the eighteenth century to recruit further generations of cryptologists, and create formal cryptology organizations that took their collective title from the French cabinet noir/ ("black chamber"). Usually located within post office buildings, the members of the black chamber would carefully open the sealed mail, make copies of suspect passages, and close the letters with forged wax seals. Then the laborious task of deciphering coded communications would begin.

Most of Europe's black chambers were closed in the mid-nineteenth century by a combination of public opinion and new social philosophies. The reading of other people's mail was seen as an infringement of personal freedom. In England public pressure forced the government to cease its opening of diplomatic mail in 1844. Four years later, the black chambers of Austria and France also ended their work.

America did not have a black chamber until the early twentieth century, and it was concerned with radio transmissions (telegraphs) rather than postal mail. Its fame is mainly due to Herbert Osborne Yardley (1889–1958), who described the inner workings of the covert organization in his book, The American Black Chamber . Yardley wrote his controversial text after the closing of the code-breaking organization in 1929. The Hoover government wanted to promote trust in international relations, and as Secretary of State Henry Stimson noted, "Gentlemen do not read each other's mail." However, by 1940, the black chamber had to be reformed (without Yardley) to counter the threat of war. Today black chambers have become electronic monitoring systems, which many governments use to monitor suspicious communications across the world.



Kahn, David, The Codebreakers: The Story of Secret Writing. New York, NY: The Macmillan Company, 1967.

Yardley, Herbert O. The American Black Chamber. Indianapolis: Bobbs-Merrill, 1931.

——. The Chinese Black Chamber, Boston: Houghton Mifflin, 1983.


Codes and ciphers
Cryptology, History

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