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In the history of cryptography, the "System 97 Typewriter for European Characters" or "Type B Cipher Machine", codenamed Purple by the United States, was an encryption machine used by the Japanese Foreign Office from February 1939 to the end of World War II. The machine was an electromechanical device that used stepping-switches to encrypt the most sensitive diplomatic traffic. All messages were written in the 26-letter English alphabet, which was commonly used for telegraphy. Any Japanese text had to be transliterated or coded. The 26-letters were separated using a plug board into two groups, of six and twenty letters respectively. The letters in the sixes group were scrambled using a 6 × 25 substitution table, while letters in the twenties group were more thoroughly scrambled using three successive 20 × 25 substitution tables.
Corregidor is an island located at the entrance of Manila Bay in the southwestern part of Luzon in the Philippines, and is considered part of the Province of Cavite. Due to this location, Corregidor has historically been fortified with coastal artillery batteries to defend the entrance of Manila Bay and Manila itself from attacks by enemy warships. Located 48 kilometres (30 mi) inland, Manila is the nation's largest city and has been the most important seaport in the Philippines for centuries, from the colonial rule of Spain, Japan, and the United States, up through the establishment of the Third Philippine Republic in 1946.
William Frederick Friedman was a US Army cryptographer who ran the research division of the Army's Signal Intelligence Service (SIS) in the 1930s, and parts of its follow-on services into the 1950s. In 1940, subordinates of his led by Frank Rowlett broke Japan's PURPLE cipher, thus disclosing Japanese diplomatic secrets before America's entrance into World War II.
The vulnerability of Japanese naval codes and ciphers was crucial to the conduct of World War II, and had an important influence on foreign relations between Japan and the west in the years leading up to the war as well. Every Japanese code was eventually broken, and the intelligence gathered made possible such operations as the victorious American ambush of the Japanese Navy at Midway in 1942 and the shooting down of Japanese admiral Isoroku Yamamoto a year later in Operation Vengeance.
Joseph John Rochefort was an American naval officer and cryptanalyst. He was a major figure in the United States Navy's cryptographic and intelligence operations from 1925 to 1946, particularly in the Battle of Midway. His contributions and those of his team were pivotal to victory in the Pacific War.
Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids. In the early 20th century, the invention of complex mechanical and electromechanical machines, such as the Enigma rotor machine, provided more sophisticated and efficient means of encryption; and the subsequent introduction of electronics and computing has allowed elaborate schemes of still greater complexity, most of which are entirely unsuited to pen and paper.
Magic was an Allied cryptanalysis project during World War II. It involved the United States Army's Signals Intelligence Service (SIS) and the United States Navy's Communication Special Unit.
Cryptography was used extensively during World War II because of the importance of radio communication and the ease of radio interception. The nations involved fielded a plethora of code and cipher systems, many of the latter using rotor machines. As a result, the theoretical and practical aspects of cryptanalysis, or codebreaking, were much advanced.
Various conspiracy theories allege that U.S. government officials had advance knowledge of Japan's December 7, 1941, attack on Pearl Harbor. Ever since the Japanese attack, there has been debate as to why and how the United States was caught off guard, and how much and when American officials knew of Japanese plans for an attack. In September 1944, John T. Flynn, a co-founder of the non-interventionist America First Committee, launched a Pearl Harbor counter-narrative when he published a 46-page booklet entitled The Truth about Pearl Harbor, arguing that Roosevelt and his inner circle had been plotting to provoke the Japanese into an attack on the U.S. and thus provide a reason to enter the war since January 1941.
OP-20-G or "Office of Chief Of Naval Operations (OPNAV), 20th Division of the Office of Naval Communications, G Section / Communications Security", was the U.S. Navy's signals intelligence and cryptanalysis group during World War II. Its mission was to intercept, decrypt, and analyze naval communications from Japanese, German, and Italian navies. In addition OP-20-G also copied diplomatic messages of many foreign governments. The majority of the section's effort was directed towards Japan and included breaking the early Japanese "Blue" book fleet code. This was made possible by intercept and High Frequency Direction Finder (HFDF) sites in the Pacific, Atlantic, and continental U.S., as well as a Japanese telegraphic code school for radio operators in Washington, D.C.
Station HYPO, also known as Fleet Radio Unit Pacific (FRUPAC), was the United States Navy signals monitoring and cryptographic intelligence unit in Hawaii during World War II. It was one of two major Allied signals intelligence units, called Fleet Radio Units in the Pacific theaters, along with FRUMEL in Melbourne, Australia. The station took its initial name from the phonetic code at the time for "H" for Heʻeia, Hawaii radio tower. The precise importance and role of HYPO in penetrating the Japanese naval codes has been the subject of considerable controversy, reflecting internal tensions amongst US Navy cryptographic stations.
The Central Bureau was one of two Allied signals intelligence (SIGINT) organisations in the South West Pacific area (SWPA) during World War II. Central Bureau was attached to the headquarters of the Supreme Commander, Southwest Pacific Area, General Douglas MacArthur. The role of the Bureau was to research and decrypt intercepted Imperial Japanese Army traffic and work in close co-operation with other SIGINT centers in the United States, United Kingdom and India. Air activities included both army and navy air forces, as there was no independent Japanese air force.
Fleet Radio Unit, Melbourne (FRUMEL) was a United States–Australian–British signals intelligence unit, founded in Melbourne, Australia, during World War II. It was one of two major Allied signals intelligence units called Fleet Radio Units in the Pacific theatre, the other being FRUPAC, in Hawaii. FRUMEL was a U.S. Navy organization, reporting directly to CINCPAC in Hawaii and the Chief of Naval Operations in Washington, D.C., and hence to the central cryptographic organization. The separate Central Bureau in Melbourne was attached and reported to General Douglas MacArthur's Allied South West Pacific Area command headquarters.
Before the development of radar and other electronics techniques, signals intelligence (SIGINT) and communications intelligence (COMINT) were essentially synonymous. Sir Francis Walsingham ran a postal interception bureau with some cryptanalytic capability during the reign of Elizabeth I, but the technology was only slightly less advanced than men with shotguns, during World War I, who jammed pigeon post communications and intercepted the messages carried.
Hut 7 was a wartime section of the Government Code and Cypher School (GC&CS) at Bletchley Park tasked with the solution of Japanese naval codes such as JN4, JN11, JN40, and JN-25. The hut was headed by Hugh Foss who reported to Frank Birch, the head of Bletchley's Naval section.
Fleet Radio Units (FRU) were the major centers for Allied cryptological and signals intelligence during the Pacific Campaign of World War II. Initially two FRUs were established in the Pacific, one at Pearl Harbor, Hawaii, called Station HYPO or FRUPAC, and the other, called Station CAST or Belconnen, at Cavite Naval Yard, then Corregidor, Philippines. With the fall of the Philippines to Imperial Japanese forces in April and May 1942, CAST personnel were evacuated to a newly established FRU at Melbourne, Australia, called FRUMEL.
Captain Eric Nave was an Australian cryptographer and intelligence officer in the Royal Australian Navy (RAN) and Royal Navy, noted for his work with joint Allied intelligence units during World War II. He served in the navy from 1916 to 1949, then served as an officer in the Australian Security Intelligence Organisation until 1959.
The Far East Combined Bureau, an outstation of the British Government Code and Cypher School, was set up in Hong Kong in March 1935, to monitor Japanese, and also Chinese and Russian (Soviet) intelligence and radio traffic. Later it moved to Singapore, Colombo (Ceylon), Kilindini (Kenya), then returned to Colombo.
Japanese army and diplomatic codes. This article is on Japanese army and diplomatic ciphers and codes used up to and during World War II, to supplement the article on Japanese naval codes. The diplomatic codes were significant militarily, particularly those from diplomats in Germany.
Naval Base Manila, Naval Air Base Manila was a major United States Navy base south of the City of Manila, on Luzon Island in the Philippines. Some of the bases dates back to 1898, the end of the Spanish–American War. Starting in 1938 civilian contractors were used to build new facilities in Manila to prepare for World War II. Work stopped on December 23, 1941, when Manila was declared not defendable against the Empire of Japan southward advance, which took over the city on January 2, 1942, after the US declared it an open city. US Navy construction and repair started in March 1945 with the taking of Manila in the costly Battle of Manila ending on March 2, 1945. Naval Base Manila supported the Pacific War and remained a major US Naval Advance Base until its closure in 1971.
References
- ↑ Parker, Frederick D. A Priceless Advantage: U.S. Navy Communications Intelligence and the Battles of Coral Sea, Midway, and the Aleutians. Fort Meade MD: Center for Cryptologic History, National Security Agency, 1993.
- ↑
- The Emperor’s Codes: Bletchley Park and the breaking of Japan’s secret ciphers by Michael Smith, page 105-106 (2000, Bantam London) ISBN 0-593-04642-0