The Purple Cipher Machine

The Purple Cipher Machine was the most complex of the Japanese cipher systems of WWII.Because Japan and Germany were sharing pertinent military information it was critical for the U.S. to crack Purple's code. The purpose of this research paper is to give the history of the Purple cipher machine, how it works, and the impact it had on World War II.
The name Purple was given to the machine by American cryptanalysists. The U.S. called it Purple because thefirst Japanese code, called Orange had increased indifficulty and went on to the color Red until the most difficult, the Purple, was reached. This was the code constructed on a machine, unlike previous codes, which were constructed with pen and paper.In Japan Purple was simply referred to as “the machine” or “J”.
Purple was a poly-alphabetic substitution system, which is a form of simple substitution cipher – every position on the disk in the machine gives a different cipher alphabet. In other words, instead of having only one cipher alphabet, this system had many.The Purple Cipher Machine had three different forms, which were classified as Type A, Type B, and Type C. Type A systems were not very complex. They used text, which was mostly in the English language. This type of cipher was normally only used for routine matters. Type B systems were a little different. They dealt mostly with economic matters throughout the world. Type B was used mostly by Japanese officials at the secondary level; those who were below the ambassador. Since there was such a wide range of economic subjects, much knowledge was needed to translate the messages of Type B systems. Type C systems had the highest level traffic with about fifty to seventy five message sent a day. Most of the messages of Purple wer!
e conveyed through system C. The ciphers sent through Type C were encrypted in a text using the Roman alphabet. This text was called romaji. Romaji was very difficult to translate beca…

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