Turing Sources

Alan Turing's Report from Washington DC, November 1942

This is a transcription of the first section of Turing's report dated 28 November 1942,
in the (British) National Archives, box HW 57/10, released from secrecy in October 2004.

See the Alan Turing Home Page for a guide to this website




Turing's report was written in Washington after the first two weeks of his top-level liaison mission to the United States. It took place just after the British victory at El Alamein marked the 'end of the beginning' of the Second World War, but also the end of Britain as an independent power. Although the United States had been a British ally for nearly a year, the alliance was very far from complete, as Turing's report indicates in grimy detail. The reference to Tunny, for instance, indicates that Turing had no idea whether he could reveal anything to the Americans about the British breakthrough with the Lorenz machine cipher.

The document consists of 28 numbered typescript pages of Turing's technical report, plus a cover page. There is also a further covering page by Major G. G. Stevens, who presumably sent it by diplomatic bag back to Britain. Stevens amply confirms the disparaging tone of Turing's report on the U. S. Navy cryptanalytic section.

Below I have transcribed Turing's cover page and the first four pages of his report, then Stevens' cover page.

You can then continue to a further page on which Turing (1) gives his (again rather negative) views on the American plans for building Bombes to break Enigma messages, and (2) comments on the possible usefulness of American machinery for purposes other than Enigma cryptanalysis, in particular for the 'Tunny' work.

For more on the context of this report, go to this page of the Alan Turing Internet Scrapbook.

This text is © Crown Copyright and is transcribed only for personal and academic research purposes.




MOST SECRET

Washington
November 28, 1942

REPORT BY DR A.M. TURING, Ph. D.

Distribution
Copy No. 1     D.D.(S)
Copy No. 2     D.D.(S)
"    "   3     Captain E.G.Hastings, R.N.
"    "   4     Professor Bayly (for Dr. Turing).



REPORT ON CRYPTOGRAPHIC MACHINERY
AVAILABLE AT NAVY DEPARTMENT WASHINGTON

GENERAL

I reached New York on Friday November 12th. I was all but kept on Ellis Island by the Immigration Authorities who were very snooty about my carrying no orders and no evidence to connect me with the F.O. They considered my official's passport insufficient in itself. They asked me very minute details about where I was to report etc. I think it might have been better from a security point of view if I had been provided with some kind of document of the kind they wanted, to say nothing of the possibility that I might have been held until Stevens or somebody identified me.

I spent a few days in New York. I saw Bayly who showed me the Telekrypton. We discussed the security of it. Bayly said he was rejecting all 'zeros' or blanks from subtractor tape. I persuaded him that this was wrong, but he said he would retain it for the present. I understood this to be on the ground that it was difficult to persuade generals that one ought not to omit the zeros. I think it is a pity but not serious. We also discussed his new method of producing the subtractor tapes, which seemed to me quite satisfactory.

I reached Washington Navy Department November 17th. Found that Ely was about to be married. Saw the machinery and had some talks on E matters. As I saw nobody working with pencil and paper, I asked if there was anyone in E who did so. Was introduced to Mrs. Driscoll at this point. I was rather alarmed; she asked me a great number of questions, to most of which fortunately I did not know the answers anyway, and told me very little, mostly I think because they weren't really doing anything. The only things that I could find they were doing with the construction of a Noskwith-replacing catalogue and a complete rod coupling catalogue for the four-wheel machine. They were using comic strips a good deal which struck me as rather pathetic.

In the Navy Department I got an an impression of a certain lack of sense of proportion, due I think to insufficient practical work. I will give an example. One of their men had been doing some rather elaborate calculations about stops on the click machine. He showed me these calculations and then asked me what was the justification for our practice of neglecting all stops in which there was no click. I gave him an explanation of the kind that he evidently wanted, and also told him that it was a case of the general principle that if you get confirmations in making inferences from a hypothesis then that hypothesis becomes more probable. It astonished me to find that they would make these elaborate calculations before they had really grasped the main principles of the thing. As a result of this and quite a number of other examples of the same sort of thing, I am persuaded that one cannot very well trust these people where a matter of judgment in cryptography is concerned. I think we can make quite a lot of use of their machinery.

**************************

I had been intending to report to Potter at Bell Laboratories without any more formality than a preliminary phone call. This was apparently all wrong. Squadron-Leader Caroe of the RAFDEL got onto me and after some phoning etc. took me to see Dr. Murray. There was some trouble because no arrangements for me to see anything other than unscrambling projects had been confirmed in writing, whereas I had come out on the understanding that I was to see everything there was in the way of speech secrecy work. Dr. Murray was very friendly about it and said that if it were confirmed from the right quarters in England that this was what I intended to do, then he could fix it. My Princeton Ph.D. was quite useful in enlisting Murray's help, so I have decided to go by the name of Dr. Turing officially whilst I am over here. As soon as we had gone Murray started to get on with arranging things for me but immediately came up against a veto on any British people visiting anything at all in the speech scrambling line. Captain Hastings then took a hand, and brought the pressure to bear on General Colton, and all now seems to be well.

A visit was made to the War Department on November 25th at the request of Colonel Friedman. You had told me to keep clear of them, so I felt in rather an awkward position. I tried to keep the discussions to probability theory which seemed harmless and about which indeed I should like to talk to them a good deal.

Colonel Friedman wanted to know something about Tunny. What is your view as to whether I should discuss this or not?

[Here follow 24 pages, mostly technical description of types of machinery]



Stevens' cover page:


D.D.(S), G.C. & C.S.

TURING'S REPORT

1. The second-last phrase on page 3. "I am persuaded....". I feel it is necessary to note that Turing was only concerned with Dr. Engstrom and his party and that his judgment of the cryptographic ability only applied to them.

2. To a certain extent his mistrust is shared by Parke and other people "upstairs". Recently Engstrom's party made a study on some J.N. 40 material and returned it with the triumphant and conclusive dictum that it had a mono-digital daily substitution.

3. Generally speaking, their attitude is so purely mechanical and mathematical that they do often fail to see the wood for the trees and do not like to admit that experience and a knowledge of immediately prior developments combined with a little manual work may often produce the answer much more quickly than machinery.

They are jokingly credited with wanting to take all traffic that comes in and subject it immediately to every known process, regardless that some of it may be P/L or in a cipher which they hold.

[signed] G.G.STEVENS
Major, G.S.

Distribution
D.D.(S) 2
Dr. Turing 1
File 1




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