Editing SIGABA (section)

==Security==
[[File:SIGABA key generator.png|thumb|Key generator for SIGABA cipher machines. In a central facility in Washington, a rotor machine at right produced randomized daily settings for SIGABA, which were recorded on [[punch card]]s using the [[IBM 513]] Reproducing Punch at left. A month's worth of keys were printed on a single sheet.<ref name="NSA"/>]]
Although the SIGABA was extremely secure, the US continued to upgrade its capability throughout the war, for fear of the Axis cryptanalytic ability to break SIGABA's code. When the German's [[ENIGMA]] messages and Japan's [[Type B Cipher Machine]] were broken, the messages were closely scrutinized for signs that Axis forces were able to read the US cryptography codes. Axis [[prisoner of war|prisoners of war]] (POWs) were also interrogated with the goal of finding evidence that US cryptography had been broken. However, neither the Germans nor the Japanese were making any progress in breaking the SIGABA code. A decrypted JN-A-20 message, dated 24 January 1942, sent from the naval [[Military attaché|attaché]] in Berlin to vice chief of Japanese Naval General Staff in Tokyo stated that "joint Jap[anese]-German cryptanalytical efforts" to be "highly satisfactory", since the "German[s] have exhibited commendable ingenuity and recently experienced some success on English Navy systems", but are "encountering difficulty in establishing successful techniques of attack on 'enemy' code setup". In another decrypted JN-A-20 message, the Germans admitted that their progress in breaking US communications was unsatisfactory. The Japanese also admitted in their own communications that they had made no real progress against the American cipher system. In September 1944, when the Allies were advancing steadily on the Western front, the war diary of the German Signal Intelligence Group recorded: "U.S. 5-letter traffic: Work discontinued as unprofitable at this time".<ref name="NSA">{{cite book| last1=Timothy| first1=Mucklow| title=The SIGABA / ECM II Cipher Machine : "A Beautiful Idea"| date=2015|publisher=Center for Cryptologic History, National Security Agency| location =Fort George G. Meade| url= https://www.nsa.gov/Portals/70/documents/about/cryptologic-heritage/historical-figures-publications/publications/technology/The_SIGABA_ECM_Cipher_Machine_A_Beautiful_Idea3.pdf?ver=2019-08-07-124409-850| access-date=6 January 2020|archive-url= https://web.archive.org/web/20170515064250/https://www.nsa.gov/about/cryptologic-heritage/historical-figures-publications/publications/assets/files/sigaba-ecm-ii/The_SIGABA_ECM_Cipher_Machine_A_Beautiful_Idea3.pdf| archive-date=15 May 2017|url-status=dead}}</ref>

SIGABA systems were closely guarded at all times, with separate safes for the system base and the code-wheel assembly, but there was one incident where a unit was lost for a time. On February 3, 1945, a truck carrying a SIGABA system in three safes was stolen while its guards were visiting a brothel in recently liberated [[Colmar, France]]. [[General Eisenhower]] ordered an extensive search, which finally discovered the safes six weeks later in a nearby river.<ref name=kahn1967>{{cite book|last=Kahn|first=David|author-link=David Kahn (writer)|title=The Codebreakers: The Story of Secret Writing|year=1967|publisher=The Macmillan Company| location= New York| isbn=978-0-684-83130-5|title-link=The Codebreakers}} {{OCLC|59019141}}</ref>{{rp|pp.510–512}}