Cryptographic History of Work on the German Naval Enigma

working at very high pressure and needed ability to think very quickly and switch constantly from one thing to another. Inspite of the strain however I think it was the right way to manage the thing - all the decisions were so bound up with technical matters that they had to be taken by the technician.

11. Paras. 4 - 10 describe the main channels of work in the hut. There were also a number of additional jobs of various kinds of which perhaps cable communication with Op. 20 G is worth special mention. When the Americans began to turn out bombes in large numbers there was a constant interchange of signal - cribs, keys, message texts, cryptographic chat and so on. This all went by cable being first encyphered on the combined Anglo-American cypher machine, C.C.M. Most of the cribs being of operational urgency rapid and efficient communication was essential and a high standard was reached on this; an emergency priority signal consisting of a long crib with crib and message text repeated as a safeguard against corruption would take under an hour from the time we began to write the signal out in Hut 8 to the completion of its decyphering in Op. 20 G. As a result of this we were able to use the Op. 20 G bombes almost as conveniently as if they had been at one of our outstations 20 or 30 miles away. This work (and most other miscellaneous jobs not falling into any very definite category) was handled by the Big Room except for the preparation of signals containing cribs which was done by the head of watch in the M.R.

B Conclusions.

12. Criticism of the way in which we ran the hut and of the mistakes we made will be reserved for Part III. Apart from such criticism however there were certain general conclusions we reached and I will set these out here.

Grade of Staff employed.

13. We adopted the policy of engaging all our clerical staff as Grade III's and letting them work their way up; unless a girl was a


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