Combined cipher machine

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The Combined Cipher Machine (also Combined Cypher Machine or Combined Coding Machine , CCM for short , German "Common Key Machine ") was a rotor key machine that was used by the British and American armed forces in the Second World War for the secret exchange of messages. For this purpose, the existing TypeX and SIGABA machines were used on the British and American sides and modified accordingly so that they were mutually compatible .

history

Shortly after the Americans were drawn into World War II by the Japanese attack on Pearl Harbor on December 7, 1941, their British allies demonstrated their most important key machine , the TypeX . Conversely, the Americans were reluctant to reveal their SIGABA (also called Electric Code Machine Mark II , or ECM Mark II ) to the British . Despite everything, there was an urgent need for secure communication with one another and, under the leadership of the US Navy , the development of a "common key machine ", called the Combined Cipher Machine, was launched.

commitment

The CSP 1600 adapter turned the American SIGABA into a CCM

The development project was completed in October 1942 and production of the CCM began in December of that year in the USA. The decision was made to continue using the machines that were already available on both sides and to make them compatible with each other with the help of specially developed adapters . A suitable adapter was built for both the British TypeX and the American SIGABA .

The adapter (picture) that turned the American machine into a CCM was called the CSP 1600 by the Navy , while the US Army called it ASAM 5 . This alternative roller set replaced the original roller set and, thanks to the modular concept, could also be easily exchanged on site, so that a regular SIGABA could be quickly converted into a CCM . Correspondingly modified machines were made available by the Americans to their Canadian and British allies as CCM Mark II .

The TypeX Mark 23 was a specially modified TypeX so that it could be used as a CCM by the British .

On the British side, the existing TypeX Mark 22 was modified accordingly to the Mark 23 (picture), so that it was identical to the CCM / SIGABA despite its completely different appearance from a cryptographic point of view .

After the CCM was initially only used in relatively small numbers for joint naval communication from November 1, 1943, from April 1944 it was used by all American and British armed forces for secure mutual communication. Even after the war it was used within NATO for a few years .

safety

Despite some cryptographic weaknesses that the CCM still had until at least the beginning of 1944, the so-called German B-Dienst did not succeed in breaking into the allied CCM radio traffic intercepted on the German side under the code name "Ulm" .

literature

Web links

Individual evidence

  1. ↑ Ralph Erskine: The 1944 Naval BRUSA Agreement and its Aftermath , Cryptologia, 30: 1, 2006, p. 6, doi : 10.1080 / 01611190500401086
  2. ↑ Ralph Erskine: Ultra Reveals a Late B-Dienst Success in the Atlantic , Cryptologia, 34: 4, 2010, p. 357, doi : 10.1080 / 01611194.2010.485412