Cryptographic History of Work on the German Naval Enigma

the register which reached them a page at a time from the R.R., the percentage chance (based on frequency etc.) of each message being a dummy. After the "dummyismus" had been done they passed the page to the Big Room, as the dummy percentage affected their work.

8. After some time, if it was a normal day, the Banburists found the alphabet, thus reducing the possible wheel orders, and the cribsters produced a crib. An extract from this (the menu) was then produced; this extract was made up either by the crib room or by the machine room - it depended on the difficulty of the job, who was on duty in the two rooms and how busy the various people were. The menu having been made and checked was sent by tube by the M.R. to the "bombe hut" - Squadron Leader Jones' section - which ran the bombes. Possible solutions were sent back by the bombe hut to the M.R. and further tested by them, using additional portions of the crib which had not been sent to the bombes. When the correct solution had been obtained giving stecker and W.O. it was passed back by the M.R. to the C.R. (or sometimes to the Banburists) who found the ringstellung and grund which completed the solution.

9. The C.R. then passed the solution to the Big Room who prepared the traffic for decoding by the D.R. The D.R. set up their machines (Typex machines modified to act as Enigmas, and producing a typed decode of the message) and decoded the traffic, messages that failed to decode (duds) being kept for further examination later. When decoded the message numbers were ticked off on a message list and the decode sent by tube to Naval Section.

10. The senior cryptographer on duty was normally Duty Officer and responsible for the work of the whole hut. In particular he had to decide when to run a crib on the bombes and how many bombes to get. In later days when the technical staff was reduced to four cribsters, the cribster on duty did all the technical work - which might involve keeping an eye on half a dozen keys - and also was in general charge. This meant


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