Radio and cryptography

Radio and cryptography

The communications system was founded by Brigadier Sir Richard Gambier-Parry, who was Head of MI6 Section VIII from 1938 to 1946 and was based at Whaddon Hall in Buckinghamshire, UK.[12] Ultra summaries from Bletchley Park were sent over landline to the radio transmitter site of Section VIII at Windy Ridge. From there they were transmitted over radio to the destination SLU.

The communications element of each SLU was called "Special Communications Unit" or SCU. Radio transmitters were constructed at Waddon Hall workshops, while receivers were the National HRO, made in the USA. The SCU's were highly mobile and the first such units used civilian Packard cars. The following SCUs are listed:[12] SCU1 (Whaddon Hall), SCU2 (France before 1940, India), SCU3 (Hanslope Park) SCU5, SCU6 (possibly Algiers and Italy), SCU7 (training unit in the UK), SCU8 (Europe after D-day), SCU9 (Europe after D-day), SCU11 (Palestine and India), SCU12 (India), SCU13 and SCU14. [13]

The cryptographic element of each SLU was supplied by the RAF and was based on the TYPEX cryptographic machine and one time pad systems.

The RN Ultra messages from the RN OIC to ships at sea were necessarily transmitted over normal naval radio circuits and were protected by one time pad encryption.[14]