CHAPTER 7
THE JAPANESE CIPHER MACHINES
THE JAPANESE introduced a family of cipher machines implementing polyalphabetic substitution early in the twentieth century. Assigned color codes by the Army Signal Intelligence Service, the first machine in this family, RED, used a half-rotor in place of the Hebern rotor. RED was soon followed by PURPLE, which derived ciphertext using stepping switches. This chapter describes these cipher machines and outlines their cryptanalysis.
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