Editing Japanese naval codes (section)

==Red code==
The Red Book code was an IJN [[code book]] system used in [[World War I]] and after. It was called "Red Book" because the American photographs made of it were bound in red covers.<ref name="goebel" >Greg Goebel. [http://vc.airvectors.net/ttcode_06.html "US Codebreakers In The Shadow Of War"]. 2018.</ref> It should not be confused with the [[Red (cipher machine)|RED cipher]] used by the diplomatic corps.

This code consisted of two books. The first contained the code itself; the second contained an additive cipher which was applied to the codes before transmission, with the starting point for the latter being embedded in the transmitted message. A copy of the code book was obtained in a [[Black-bag cryptanalysis|"black bag" operation]] on the luggage of a Japanese naval attaché in 1923; after three years of work [[Agnes Driscoll]] was able to break the additive portion of the code.<ref>{{cite book|title=Military Communications: From Ancient Times to the 21st Century|first= Christopher H.|last=Sterling|publisher=ABC-CLIO|year=2007|pages=126–127|url=https://books.google.com/books?id=RBC2nY1rp5MC&pg=PA127|access-date=2009-05-01|isbn=978-1-85109-732-6}}</ref><ref>{{cite web|title=Red Code|url=http://www.espionageinfo.com/Pr-Re/Red-Code.html|access-date=2009-05-01|archive-date=8 May 2009|archive-url=https://web.archive.org/web/20090508150516/http://www.espionageinfo.com/Pr-Re/Red-Code.html|url-status=dead}}</ref>{{sfn|Budiansky |2000|p=5}}

Knowledge of the Red Book code helped crack the similarly constructed Blue Book code.<ref name="goebel" />