![]() ![]() ![]() When SIS personnel had solved the PURPLE system, they came up with the concept of building their own version of the machine for faster decryption, a device they called the "PURPLE ANALOG." An electrical engineer in SIS named Leo Rosen produced a prototype, according to legend, constructed in his basement. ![]() According to the story, Friedman chose this codeword because he liked to describe his cryptanalysts to outsiders as "magicians." Decrypts were marked with the codeword "MAGIC" to show they needed extra protection. Once the system had been solved, William Friedman established what may have been the first compartment for intelligence information in the U.S. Genevieve Grotjan, Albert Small, and Samuel Snyder, junior cryptanalyts, also made important contributions in solving the system. The solution of PURPLE was a team effort, under the overall direction of William Friedman, with Frank Rowlett leading the day-to-day efforts. The Americans capitalized on both mistakes to develop cribs for analyzing the system. Furthermore, they enciphered English-language diplomatic texts The Japanese also made two elementary mistakes in procedure: since RED and PURPLE were used at different overseas posts, they frequently sent the same message enciphered in both systems. Once this 20/6 split was recognized, the basic attack against PURPLE was cribbing. The machines split the Japanese syllabary into vowels and consonants, and enciphered each separately. The machines had a basic weakness that eventually became one of the keys to its exploitation by U.S. Some good intelligence was still obtained from RED, but the material the Americans most wanted was now enciphered on the PURPLE machine. Some posts, such as Washington, had both machines, enabling lateral communications with other overseas missions as well as directly with Tokyo. PURPLE was used for communication with major diplomatic posts - Washington, London and Moscow, among others - and RED for less important locations. In fact, RED and PURPLE machines were used simultaneously. In late 1938, a cipher expert traveled to Japan's major overseas diplomatic posts to install a new cryptodevice, called the "Type B Machine." Japan's Foreign Ministry introduced this new equipment in February 1939 U.S. However, this kind of close access ended abruptly. policymakers the details of a secret clause in this tripartite treaty which committed each country to support the others in war "regardless of the circumstances." A decrypted Japanese diplomatic message of November 1936 revealed to U.S. For example, senior American leaders, as might be expected, were anxiously watching Japanese negotiations with Germany and Italy, which eventually resulted in the Anti-Comintern Pact of 1936. government insight into Japanese foreign policy and practice. ![]() Translations of RED messages gave the U.S. SIS, which had been studying machine systems in anticipation of developments such as this, produced its first translation from a RED machine decrypt in February 1937. military at that time for plans and programs, so it seemed only natural to the SIS staff to adopt the first color of the spectrum for the first machine cryptosystem they worked on. Army's Signal Intelligence Service (SIS) first encountered intercept from the "Type A" machine in 1935, the personnel nicknamed the system "RED." Color nicknames were used extensively in the U.S. The Foreign Ministry in 1935 adopted a device called the "Type A Machine" to protect its communications. Embarrassed by Herbert Yardley's revelations in his 1931 book The American Black Chamber, the Japanese Foreign Ministry turned increasingly to machine systems to encipher its messages. ![]()
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