Cipher Wheel of The Meiji Era's Cryptographic Wheel

On 14 September (9 August) of 1869 (Meiji 2), Japan's first telegraph operations began service linked Tokyo and Yokohama. By the early 1880s, the country's telegraph network was extended to all the major parts of the Japanese archipelago. At that time, it was highly valued as the newest high-speed media by the government bureaucracy (particularly public security) and for the transmission of economic information. Still, there was on problem involving telegrams; the information transmitted could be read by a third party, namely, the telegraph operator. For example, in one passage of Alexandre Dumas's "The Count of Monte Cristo," a worker for the telegraph company is bribed to relay false information. In any event, to have the contents of a telegram read by an unknown operator produced much anxiety.

Therefore, shortly after the beginning of the telegraph business, the transmission of coded information was authorized and used widely in Japan. During the late Meiji era, collections of codes were even put on sale that were full of market related terms for use in the transmission and receipt of economic information.

Codes were also used by government bureaucracies when relaying information; codes are found in historical documents from around 1875 (Meiji 8). The Papers of MISHIMA Michitsune include several code charts used in communications between the Home Ministry, the Finance Ministry, and prefectural governors offices. All of these consisted of a one-to-one assignment of the original uncoded character ("alphabet") to the corresponding code "alphabet" (designated code "alphabet", "substituted 'alphabet'", "replacement 'alphabet'") (in a single substitution encryption chart). The early coded messages were uncomplicated, whereby instead of using sequentially the standard ordering of the forty-eight "alphabets" in the "i·ro·ha" phonetic (tonal) syllabary that begins with "i", the coded message started with the last "alphabet" , "un", or, by substituting for it the proper sequence of the forty-four "a·i·u·e·o" phonetic (tonal) syllabary with "a" being the replacement of "i" in the message. Beginning in March 1879 (Meiji 12), more effort was placed into encoding by using irregular arrangements of the "alphabets", making them more difficult to decode (in cryptology, a more complicated code is said to have a high "encryption level", while decoding is called, "breaking a code").

One of the more notable codes used by the Government was the cryptographic wheel established in November 1879 (Meiji 12). It comprised of two round discs, one small one on top of a bigger one, with a window on the small one, showing the numbers one through five in Chinese characters spaced at given points underneath. This system allowed for the use of five different code charts. It was also very convenient, as the uncoded "alphabet" (on the small disc) corresponding to the coded letters (on the large disc) were placed vertically each other for instant reference (if you can get a digital image of the code dial; I would recommend to those interested in making a reproduction to print it out and paste it on cardboard or pasteboard). Though I would like to say that this was a brilliant example of what can be done in a low-tech era, the ingenuity of the idea is detracted somewhat by its oversimplified encryption manner (the uncoded "alphabet" on the small disc are arranged in the "i·ro·ha" sequence in clockwise fashion, while the coded letters on the larger disc are simply arranged in the same order but counterclockwise). In the late Showa 30's, there was a similar cryptographic wheel included in the "Boys' Detective Set" of in the magazine "Shonen", and I believe it had an even higher encryption level than the one used in the Meiji era.

Notification from the Minister of the Treasury (OKUMA Shigenobu) to Prefectures regarding Code Changes November 12, 1879 (Meiji 12)Papers of MISHIMA Michitsune, #474-10