Wednesday, April 23, 2014

Typex cipher machines for the Polish Foreign Ministry

In 1926, the British Government set up an Inter-Departmental Cypher Committee to investigate the possibility of replacing the codebooks then used by the armed forces, the Foreign Office, the Colonial Office and the India Office with a cipher machine. It was understood that a cipher machine would be inherently more secure and much faster to use in encoding and decoding messages. Despite spending a considerable amount of money and evaluating various models by 1933 the committee had failed to find a suitable machine. Yet the need for such a device continued to exist and the Royal Air Force decided to independently fund such a project. The person in charge of their programme was Wing Commander Lywood, a member of their Signals Division. Lywood decided to focus on modifying an existing cipher machine and the one chosen was the commercially successful Enigma. Two more rotor positions were added in the scrambler unit and the machine was modified so that it could automatically print the enciphered text. This was done so these machines could be used in the DTN-Defence Teleprinter Network.

The new machine was called Typex (originally RAF Enigma with TypeX attachments). In terms of security it was similar to a commercial Enigma but had the additional security measure of multiple notches per rotor. This meant that during encipherment the rotors moved more often than in the standard Enigma machines. 
In the period 1939-45 the Typex was one of the main high level British crypto systems. According to documents found in British national archives HW 40/221 ‘Poland: reports and correspondence relating to the security of Polish communications’, it seems that the Polish government in exile learned about Typex and was interested in buying a small number of machines in 1944.

During WWII the Polish foreign ministry relied on enciphered codebooks for its secret communications. Perhaps they were interested in Typex because they considered their own systems insecure. Whatever the reason it doesn’t seem like they were given any machines since the report says ‘the supply position in respect of Type X is such that it is probably impossible to meet their requirements for the time being
It is interesting to note that the same report says ‘provided the Type X machines supplied were not fitted with Plugboard and provided also we wired for them and supplied the necessary drums, the advantages to be gained by meeting their request would outweigh the disadvantages’.


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