Editing Ultra (cryptography) (section)

===Japanese===
In the [[Pacific Ocean|Pacific]] theatre, a Japanese cipher machine, called "[[Purple code|Purple]]" by the Americans, was used for highest-level Japanese diplomatic traffic. It produced a polyalphabetic substitution cipher, but unlike Enigma, was not a rotor machine, being built around electrical [[stepping switch]]es. It was broken by the US Army [[Signal Intelligence Service]] and disseminated as ''[[Magic (cryptography)|Magic]]''. Detailed reports by the Japanese ambassador to Germany were encrypted on the Purple machine. His reports included reviews of German assessments of the military situation, reviews of strategy and intentions, reports on direct inspections by the ambassador (in one case, of Normandy beach defences), and reports of long interviews with Hitler.{{sfn|Hinsley|1993a|p=}} The Japanese are said to have obtained an Enigma machine in 1937, although it is debated whether they were given it by the Germans or bought a commercial version, which, apart from the plugboard and internal wiring, was the German ''Heer/Luftwaffe'' machine. Having developed a similar machine, the Japanese did not use the Enigma machine for their most secret communications.

The chief fleet communications code system used by the Imperial Japanese Navy was called [[JN-25]] by the Americans, and by early 1942 the US Navy had made considerable progress in decrypting Japanese naval messages. The US Army also made progress on the [[Japanese army and diplomatic codes|Japanese Army's codes]] in 1943, including codes used by supply ships, resulting in heavy losses to their shipping.