Donald W. Davies

The bombe—a remarkable logic machine

The bombe was an electromechanical machine devised by Alan Turing and Gordon Welchman for breaking the. German Enigma cipher in World War II. The way in which it used a reductio ad absurdum logic to reduce 263 possibilities to a few is a unique example of ingenious circuit design, which is described in detail. Its relationship to the Polish version of the ‘bombe’ is explored. The importance of the diagonal board is shown as is the threat that this device faced from the Germans use of the ‘Enigma-Uhr’.

THE LORENZ CIPHER MACHINE SZ42

The German cipher traffic called tunny which was broken at Bletchley Park using the Colossus machine was produced bu an in-line “cipher-attachment” made by Lorenz, Schlussel Zusatz or SZ42. This paper is a description of the way that the SZ42 operates and its mechanism.

EFFECTIVENESS OF THE DIAGONAL BOARD

The bombe was an electromechanical machine devised by Alan Turing and Gordon Welchman for breaking the German Enigma cipher in World War II. Welchmans contribution was the ‘diagonal board’ and it was vital to its success. The device reduced the number of times that the bombe stopped for an apparent solution which was not valid. The ratio by which the false stops were reduced is calculated in this paper. The work showed that there remained a class of false stops which had not been eliminated and further investigation showed that an attachment called the ‘machine gun’ helped to reduce the time lost for this reason. While this work was in progress, numerical results derived by Turing became available, but he did not give the theory and these are consistent (apart from apparent numerical errors) with our results.

NEW INFORMATION ON THE HISTORY OF THE SIEMENS AND HALSKE T52 CIPHER MACHINES

Two earlier papers in Cryptologia [1, 2] described the WWII German on-line cipher machine known as T52. The circuit which controls the irregular movement of the cam wheels appeared in two forms and it seemed likely that alterations had been made. The reason for these alterations can now be explained. The paper which follows this one is from the person who made the changes.

THE SIEMENS AND HALSKE T52E CIPHER MACHINE

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THE EARLY MODELS OF THE SEIMENS AND HALSKE T52 CIPHER MACHINE

ISSN: 0161-1194 (Print) 1558-1586 (Online) Journal homepage: http://www.tandfonline.com/loi/ucry20 THE EARLY MODELS OF THE SEIMENS AND HALSKE T52 CIPHER MACHINE DONALD W. DAVIES To cite this article: DONALD W. DAVIES (1983) THE EARLY MODELS OF THE SEIMENS AND HALSKE T52 CIPHER MACHINE, Cryptologia, 7:3, 235-253, DOI: 10.1080/0161-118391857964 To link to this article: http://dx.doi.org/10.1080/0161-118391857964

An unidentified cipher device

ABSTRACT A description of a simple cipher device, similar in some ways to Wheatstones Cryptograph.

BOLTON'S CYPHER WHEEL

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.