Abstract
The Imperial Japanese Navy IKA cipher machine was a predecessor to the more familiar Japanese cipher machines of the 1931 and 1937 series. Nothing is known about the machine itself, but the cryptography of the machine is known. What follows describes the cryptography of the IKA machine and discusses that machine in the context of the 1931 and 1937 series of Japanese cipher machines that followed it.
Highlights
IJN Cipher MachinesIn the 1930s and 1940s, the Imperial Japanese Navy used a succession of three cipher machines for secret administrative matters among shore stations
The Japanese language can be written in three different sets of characters
In the 1930s and 1940s, the Imperial Japanese Navy used a succession of three cipher machines for secret administrative matters among shore stations
Summary
In the 1930s and 1940s, the Imperial Japanese Navy used a succession of three cipher machines for secret administrative matters among shore stations. If the Aposition on the half-rotor disk were in contact with the A-position on the output disk, the ciphertext typewriter would type an A. If plaintext A were typed in the initial position of the half-rotor, the corresponding ciphertext letter would be A. If the half-rotor stepped one position for each letter, the rows of the enciphering table correspond to the six successive encipherings of the plaintext letters which are shown in the table. It notes that until 1936 IKA might have been known as M-1 and ORANGE as M-2
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