The Black Chamber, officially the Cable and Telegraph Section and also known as the Cipher Bureau, was the first peacetime cryptanalytic organization in the United States, operating from 1917 to 1929. It was a forerunner of the National Security Agency (NSA).
History
thumb|right|Black Chamber cryptanalytic work sheet for solving a [[Empire of Japan|Japanese diplomatic cipher, 1919]]
Until World War I, the only codes and cypher organizations created by the U.S. government were short-lived agencies of the United States Armed Forces, such as the U.S. Army's Military Intelligence (MI-8).
The Cable and Telegraph Section or Cipher Bureau was established on April 28, 1917, three weeks after the U.S. Congress declared war on the German Empire and began American involvement in World War I. It was headquartered in Washington, D.C., operated under the executive branch without direct Congressional authorization, and was moved in the Army's organizational chart several times. On July 5, 1917, Herbert O. Yardley was assigned to head the Cipher Bureau, which consisted of Yardley and two civilian clerks. It absorbed the Navy's cryptanalysis functions in July 1918.
The Cipher Bureau moved to New York City on May 20, 1919, where it continued intelligence activities as the Code Compilation Company, or the Black Chamber, under Yardley's command. Jointly funded by the Army and the State Department, the Cipher Bureau was tasked with breaking the communications of other nations, primarily diplomatic communications, as occurred during the Washington Naval Conference.
According to intelligence historian James Bamford, the Black Chamber secured the cooperation of American telegraph companies such as Western Union in illegally turning over the cable traffic of foreign embassies and consulates. Eventually, "almost the entire American cable industry" was part of this effort. However, these companies eventually withdrew their support, possibly due to the Radio Act of 1927, which broadened criminal offenses related to breaching the confidentiality of telegraph messages.
In 1929, the State Department withdrew its share of the funding while the Army, undergoing unit reorganizations, transferred the Black Chamber to the Signal Corps, which opted to rebuild the organization for their own purposes and dismissed Yardley and all of his employees. Stimson's ethical reservations about cryptanalysis focused on the targeting of diplomats from the U.S.'s close allies, not on spying in general. Once he became Secretary of War during World War II, he and the entire U.S. command structure relied heavily on decrypted enemy communications.