Cryptographic History of Work on the German Naval Enigma

easy and many of us in Hut 8 felt that the magnitude of Turing's contribution was never fully realized by the outside world.

8. In November we at last started to read the U-boat traffic breaking into a Shark day on a W.W. (short weather report). For the next six months we were to break most Shark days on short signals, first on W.W. and then on B'B' (B bars) so, a short explanation of their general nature and function is under.

9. For various reasons - chiefly speed and desire to avoid our direction finders - the enemy wished to be able to send out information in as concise a form as possible, particularly when on operational duty. His chief ways of doing this were by long E bars, short E bars, B bars and W W's. This account will be confined to W W's and B bars since these were the only types of major importance to us and the latter superseded long and short E bars entirely.

10. A decoded W W message consisted of a series of weather readings recorded in a standard order; the information was sent in a shorthand system given in the "Wetterkurz schluessel". For example, in the second edition of the book table 9, i.e. the table corresponding to the 9th letter of the message, gave "Direction and type of swell". There were 8 directions (N, N.E, E etc.) and three types of swell (Low, Moderate and Heavy) making 24 possibilities represented by the letter A to X. Y stood for no swell and Z for "confused". Thus if the 9th letter of the message is K this says "Swell moderate and in direction E".

11. W W's were normally sent in response to a signal (sent on Shark keys) from the control station saying (for example) "Witzendorf to report weather between 0300 and 0600 tomorrow morning". Witzendorf sent in the W W as ordered and an acknowledgment would then be sent from control saying "Short weather signal has been received from Witzendorf at 04.16 hours". After decoding Witzendorf's message,


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