JOINT BASE SAN ANTONIO-LACKLAND, Texas –
The Dr. Dennis F. Casey Heritage Center inside 25th Air Force Headquarters is a hidden gem filled with iconic twentieth century cipher mechanisms.
The multiple award-winning exhibits feature the World War II German Enigma, American Sigaba and Cold War Soviet Fialka cryptographic machines. The newest addition to the collections is a World War II Purple Analog unveiled Dec. 21.
The new exhibit features a specially-configured input keyboard from the Purple Analog system. This system was used by U.S. Army cryptanalysts to decode diplomatic messages sent on the Japanese World War II cryptographic system known to codebreakers as Purple.
This input device was one of three components in a configuration used to decrypt diplomatic messages sent between Japan and its embassies around the world. The Japanese began using the Purple code in early 1937.
The U.S. Army’s Signal Intelligence Service cryptanalysts began working on the Purple’s code in February 1939, making their first successful break into the system in September 1940, when they isolated patterns in the codes. They attributed their success to the poor security practices of Japanese cipher clerks.
Such security breaches enabled American cryptographers to first design a pen and paper analog, allowing them to consistently break the Purple code.
The Signal Intelligence Service’s talented personnel also designed an analog machine to enable the expedient decryption of Purple-based messages. This cryptologic breakthrough was one of the key components in the Allied success in the Pacific, because it ensured the United States had unfettered access to Japanese diplomatic messages as well as the Imperial Naval codes.
Despite tip-offs from the Germans, the Japanese government remained unaware the United States had broken the Purple code and continued to use it until the end of the war in 1945. The information derived from Purple communications was code named “Magic,” and it provided critical intelligence information in both the Pacific and European theaters of war.
All of the cryptologic devices displayed in the Heritage Center are on loan from the National Cryptologic Museum, Fort George G. Meade, Maryland.