| Tittel: | Decoding Pearl Harbor : USN Cryptanalysis and the Challenge of JN-25B in 1941 | | Ansvar: | Timothy Wilford | | Forfatter: | Wilford, Timothy  | | Materialtype: | Artikkel | | Signatur: | Digital PDF | | Utgitt: | Canada : Canadian Nautical Research Society / North American Society for Oceanic History, 2002 | | Omfang: | 21 sider | | Klassenummer: | 940.54 | | Serie: | The Northern Mariner/ Le marin du nord ; 1/2002 | | Emneord: | 2. verdenskrig / Andre verdenskrig / Flyangrep / JN-25B / Kode / Kodesystem / Krig / Kryptoanalyse / Kryptografi | | Geografiske emneord: | Hawaii / Japan / Pearl Harbor / USA | | Note: | Artikkelen ligger kun som nedlastbar PDF på høyre side. | | Innhold: | ----------------------------------------------------------------------------------------------------
"We are reading enough current traffic to keep two translators very busy," explained Lt. John Lietwiler to the Navy Department in a letter dated 16 November 1941, in which he discussed American efforts to decrypt the principal Japanese naval code.' The Japanese named this code Kaigun Ango – Sho D, but in 1941 American cryptanalysts referred to it as the 5-Numeral Code or AN-1 Code, although it was later known in Allied wartime reports as JN-25B. Lietwiler was co-commander of Station Cast, a United States Navy (USN) radio intelligence station located on the island of Corregidor in the Philippines. One of his primary responsibilities in late 1941 was the penetration of JN-25B. The Imperial Japanese Navy sent the bulk of its encrypted radio messages in this code and, needless to say, the Navy Department in Washington wanted to read these messages, despite its limited cryptanalytic resources. New evidence released by the National Archives II in College Park, Maryland, sheds light on the controversial question of how well the USN could read Japanese naval traffic in late 1941. Certainly, Navy cryptanalysts faced many obstacles in their quest to understand Japanese intentions in the Far East. Yet on the eve of the Pearl Harbor attack, USN cryptanalysts could partially read JN-25B, a code in which the Japanese transmitted numerous messages suggesting their intention to conduct a trans-Pacific raid against anchored capital ships.
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