Gordon Welchman
Page 33
It is clear that, although the designers of the Enigma with which Hut 6 had to deal may be accused of not having done a perfect job, the real culprits were the people who laid down the operating procedures, the people who were communicating with each other, and the cipher clerks who operated the machines. The machine as it was would have been impregnable if it had been used properly.
In his book, he went on to describe the comedy of errors committed by the Germans. As with almost all of the technical detail in his book, Welchman had written this section from memory, without help from former colleagues or official documents. Inevitably there were errors in his manuscript and in early August 1982 he received a letter from Dennis Babbage, one of the first recruits to BP, arriving just after Christmas 1939. Once established in Hut 6, he had quickly become head of Hut 6’s research section and the chief cryptanalyst. Most colleagues regarded Babbage and David Rees as Hut 6’s technical wizards.
Babbage had read The Hut Six Story and had felt compelled to write to Welchman, pointing out some of the errors in the book. He attached what he described as a short monograph on the subject of cillies. As there does not appear to be any account of Hut 6 activity in existing literature directly attributable to Babbage, his monograph is included below in its entirety:
Sillies
I think that these were originally christened Cillies (perhaps by Dilly Knox?). They were not as described in pp. 99–103 [of The Hut Six Story]. If we had a 3-part message like that at the bottom of page 99 we should of course have guessed the text settings, but this wasn’t a true cilli, and I don’t remember anything quite so obvious occurring.
The essential thing about a cilli operator was that when he had encoded a message he would leave the wheels unaltered when he came to encode the text setting of his second message (or second part of the same message). If he had done this then by ‘alphabetical subtraction’ of the number of letters in the first message from the 3-letter indicator setting of the second we would get back to the text setting of the first message and thus have a 3-letter decode. The nature of this ‘alphabetical subtraction’ depended on the wheel-order. When a wheel advanced from one letter to the next, the wheel (if any) on its left would normally stay put, but when the first wheel passed through a certain ‘critical position’ it would take its left-hand neighbour with it. The critical positions for wheels 1, 2, 3, 4, 5 were Q/R, E/F, V/W, J/K, Z/A respectively.
Suppose we had a 5-part message whose indicator settings and indicators were as follows, where the figures in brackets give the number of letters in the text:
AVS MBU (161)
QGD LRT (166)
XZH FJK (167)
EKN YTL (171)
RMK BHC (150)
If we subtract 161 (or 6 × 26 + 5) ‘alphabetically’ from QGD we get QAY. 166 (or 6 × 26 + 10) from XZH gives XTX. 167 (or 6 × 26 + 11) from EKN gives EEC and 171 (or 6 × 26 + 15) from RMK gives RGV. QAY, XTX, EEC, RGV are very nearly the four consecutive ‘keyboard diagonals’ QAY, WSX, EDC, RFV, and we can in fact get back to these by ‘alphabetical subtraction’ if we make certain assumptions about the wheel order. Let us assume that we are dealing with a cilli operator and that the text settings of the first four parts are QAY, WSX, EDC, RFV. We get from QAY to QGD in 6 × 26 + 5 steps provided the right-hand wheel does not pass through a critical position in going from Y to D. If it does pass through such a position we arrive at QHD (or at RHD if also the middle wheel passes through a critical position in going from A to H). If the middle wheel has a critical position between A and G and the right-hand one does not have one between Y and D, we arrive at RGD. We deduce that the middle wheel is not 2 and that the right wheel is not 5. In order to get from WSX to XZH in 6 × 26 + 10 steps the middle wheel must have a critical position between S and Z, and the right-hand wheel must have one between X and H. Hence the middle wheel must be 3 and the right-hand one 5 or 2. The above assumptions lead us to the conclusion that the wheel order is 132 or 432 or 532, and it may be verified that with any of these wheel orders one does get from EDC to EKN in 167 steps, and from RFV to RMK in 171 steps.
Thus we have a 12-letter decode, or rather a 15-letter one, because we may assume with some confidence that the text setting of the fifth part is TGB, which is the fifth in the sequence of ‘keyboard diagonals’. In searching for the stecker pairings we have only 3 wheel orders to consider instead of 60, and a strong Herivel tip might reduce the number of ringstellungs to be considered from 26 × 26 × 26 to 1, at any rate as a first shot. I distinctly remember just such a situation occurring one day and my working out the machine setting by myself well before 7 a.m.
Apart from triads of letters forming recognizable patterns on the keyboard, some lazy cilli operators chose text settings three steps ahead of the indicator, not so much JAB JAB as JAB JAE, the point being that, after the text setting had been encoded, the wheels would be in the correct position for encoding the main text.
Other popular text settings were pronounceable 3-letter groups. One was SAK, which I suspect means something rather rude.
In searching for cillies of all these kinds one examined a sequence of messages from the same operator and carried out what I have described as alphabetical subtraction combined with intelligent guesswork about the wheel order. Perhaps Dilly Knox found a pronounceable sequence including CIL, short for CILLI, a girl’s name?
Appendix 4
German Air Force/Army Keys Identified and Broken*
German Air Force Keys
German Army Keys
First Seen by Year
Last Seen by Year
Key Breaks
* Source: The History of Hut 6 Volume II, HW 43/71. Some obvious literal errors in the original have been corrected.
Appendix 5
Letter from Sir Peter Mary church
Appendix 6
Welchman’s Publications
Academic Works
‘The Number of Contact Primes of the Canonical Curve of Genus p’, Proceedings of the Cambridge Philosophical Society, Vol. XXVI, Part 4, 1930, pp. 453–7
‘On Elliptic Quartic Curves with Assigned Points and Chords’, Proceedings of the Cambridge Philosophical Society, Vol. XXVII, Part 1, 1931, pp. 20–3
‘Some Enumerative Results for Curves’, Proceedings of the Cambridge Philosophical Society, Vol. XXVIII, Part 1, 1932, pp. 18–2
‘Note on the Trisecants and Quadrisecants of a Space Curve’, Proceedings of the Cambridge Philosophical Society, Vol. XXVIII, Part 2, 1932, pp. 206–8
‘Plane Congruences of the Second Order in Space of Four Dimensions and Fifth Incidence Theorems’, Proceedings of the Cambridge Philosophical Society, Vol. XXVIII, Part 3, 1932, pp.276–84
‘Additional Note on Plane Congruences and Fifth Incidence Theorems’, Proceedings of the Cambridge Philosophical Society, Vol. XXVIII, Part 4, 1932, pp. 416–20
‘Foci of Systems of Space’, Journal of the London Mathematical Society, Vol. 7, Part 3, 1932, pp.175–9
‘Planar Threefolds in Space of Four Dimensions’, Proceedings of the Cambridge Philosophical Society, Vol. XXIX, Part 1, 1933, pp. 103–15
‘Incidence Scrolls’, Proceedings of the Cambridge Philosophical Society, Vol. XXIX, Part 2, 1933, pp. 235–44
‘Bisecant Curves of Ruled Surfaces’, Proceedings of the Cambridge Philosophical Society, Vol. XXIX, Part 3, 1933, pp. 382–8
‘Special Scrolls and Involutions on Canonical Curves’, Proceedings of the London Mathematical Society, Vol. 40, Ser. 2, 1936, pp. 143–88
Introduction to Algebraic Geometry, Cambridge University Press, 1950
Technical Papers
Gordon Welchman wrote many detailed technical reports while working for the MITRE
Corporation, many of which were classified. The following is a selection of such publications which were eventually approved for public release.
‘Characteristics of Air Offense Missions Against Ground Targets in Two Broad Categories of Limited War’, WP-5, 19 August 1965
/> ‘Mission and Military Value of the Airborne Tactical Air Support Team (ATAST)’, WP-673, 14 June 1966
‘A Concept for the Employment of Unit Digital Messages in a Tactical Command, Control, and Communications System’, WP-858, 10 October 1966
‘ESD/MITRE Interest in Computer-Managed Integration of Avionics Systems’, WP-1312, 20 February 1967
‘Selective Access to Tactical Information’, M70-74, August 1970. Subsequently published in Signal magazine.
‘A Concept of Selective Access to Tactical Information’, M70-97, December 1970
‘Latent Capabilities for Decision Making in a Dynamic Environment’, M70-101, December 1970
‘An Integrated Approach to the Defence of West Germany, an Information Paper’, February 1974. Subsequently published in the RUSI Journal (Royal United Services Institute for Defence Studies)
‘Alternatives in Air Strategy in Central Europe – A Background Study’, M73-103, 5 March 1974
‘A Soviet Master Plan and Its Prelude’, M74-242, 15 October 1974
‘A Five-Level Structure of NATO Ground Forces’, June 1975
Works on Bletchley Park and Enigma
The Hut Six Story, Breaking the Enigma Codes, McGraw-Hill Book Company, United States, 1982
The Hut Six Story, Breaking the Enigma Codes, Allen Lane, Great Britain, 1982
The Hut Six Story, Breaking the Enigma Codes, Penguin, Great Britain, 1984
The Hut Six Story, Breaking the Enigma Codes, M. & M. Baldwin, 1997
‘From Polish Bomba to British Bombe: The Birth of Ultra’, Intelligence and National Security, Vol. 1, No. 1, January 1986
Notes
Abbreviations: GW – Gordon Welchman; NW – Nick Welchman;
SW – Susanna Welchman; RW – Rosamond Welchman
Prologue
1. Letter to the editor, Guardian, 29 November 1985.
Chapter 1: Origins: From Algebraic Geometry to Cryptography
1. NW provided the author with a written account of memories of his father’s life from his childhood to December 1954.
2. Obituary, Sidney Sussex College Annual 1986.
3. Cambridge University Madrigal Society programmes – e.g. a performance of motets, King’s College Chapel, Sunday, 16 February 1935.
4. A Cambridge friend recalled visiting him in Newburyport in 1981 when Welchman had remembered that it was Schubert’s birthday and had suitable tapes to play in the car during a long journey.
5. Interview with Diana Lucy and Bunny Westcott.
6. When it was eventually published in 1950, it looked like a book out of its time as the subject had undergone considerable changes in the 1940s.
7. This had risen to 62 per cent in 2007.
8. Betty Huntley-Wright went on to have a long career on stage, chiefly in comedy and pantomime, as well as film, radio and television. She memorably played Mrs Twitchen in the fifth episode of the legendary British television series Fawlty Towers. In 1955, Welchman took his son and one of his daughters to see a Christmas pantomime in which Betty was appearing with her daughter and they all met after the show. They remained friends and corresponded regularly for the rest of GW’s life.
9. Copy provided by RW.
10. Note on ‘control of interception’, n.d. [c. 1924] (TNA, WO 32/4897).
11. See Keith Jeffrey’s official history MI 6: The History of the Secret Intelligence Service 1909–1949, pp. 213–14. His source is referenced as ‘Denniston, “Government and Code Cypher School”, 49’.
12. TNA, HW 62/21.
13. Strachey had been born in 1874 and, after being educated at Oxford, had worked in Military (Army) Intelligence, MI 1, during the First World War and in GC&CS between the wars. In 1934, Strachey and Hugh Foss, another GC&CS veteran, broke the Japanese naval attaché machine cipher. He would go on to head the ISOS (Illicit/Intelligence Services Oliver Strachey) section at BP, decrypting messages on the Abwehr (German secret police) network and was involved with turned German agents as part of the Double Cross system.
In January 1942, Strachey went to Ottawa, Canada, where he was chief cryptographer in the Examination Unit, and remained there until July. This ambiguously named, top secret cipher department was the Canadian version of BP. His predecessor at the unit was the notorious Herbert Osborne Yardley, who had written a sensational exposé of American and British cryptography in the First World War, The American Black Chamber, in 1931. Yardley’s contract was not renewed under pressure from Washington and Strachey refused to go to Ottawa until Yardley had left the city. Strachey brought with him from England keys to high-level Vichy French and Japanese diplomatic codes, which helped initiate closer co-operation between Washington and London. Although he did not speak or read Japanese, he helped break the Japanese encryption, which was very complex, since it used variations of kanji, hiragana, and romanization. See David Kahn’s biography of Yardley for more detail on Strachey.
14. John Tiltman could lay claim to being one of the greatest cryptologists of his generation. Born in 1894, he was offered a place at Oxford when he was thirteen but did not take it up as his father had recently died. He left school at the end of 1911 to become a teacher. Following a distinguished career in the First World War, he was sent on an elementary Russian language course which would change his life. On 1 August 1920 he was seconded for two weeks to GC&CS to help with a backlog of translation work. He took to decryption work so well that the War Office posted him to GC&CS, initially for a year, and he never returned to conventional regimental duties. A biography of Tiltman is long overdue and his accomplishments are too numerous to cover here. He continued working for GCHQ after the war until his retirement in 1964. He was immediately asked to join the NSA as he was living in the USA and served until 1980 when he was eighty-six! He was honoured by the Directors of GCHQ and NSA for his ‘uncountable contributions and successes in cryptology’ and for setting ‘exemplary standards of professionalism and performance in cryptology’.
15. See Collected Writings of John Maynard Keynes (Cambridge University Press).
Chapter 2: Bletchley Park: The First Four Months
1. TNA, HW 62/21.
2. There remains some question about whether or not Sinclair purchased BP with his own money. Jeffrey’s official history of MI 6is not explicit on the matter. In any event, an HM Land Registry document exists dated 13 June 1938 showing the first part of the transfer of BP from Faulkner to Sinclair for £6,000. The transfer is signed by Hubert Faulkner of 112 Simpson Road, Bletchley, Bucks, and Admiral Sir Hugh Sinclair of 21 Queen Anne’s Gate, Westminster, London SW1. This Westminster address was the Passport Control Office and Hugh Sinclair had a flat within the premises that backed onto 54 Broadway, the headquarters of both his SIS & GC&CS. Sinclair had a connecting passage built between the two buildings leading to his offices on its fourth floor.
3. The British patent was specification no. 267,472 and was accepted on 11 August 1927. It provided exact details of the workings of an electrical encrypting machine.
4. The origins of this story appear to be Hugh Foss’s ‘Reminiscences on Enigma’, written in 1949. In her biography of Knox, Mavis Batey confirms that GC&CS was in possession of a machine in 1929 after Foss completed his work on it. However, as an Enigma machine cost around £3,000 in today’s values in the mid-1920s it seems unlikely that Knox would have purchased one with his own money. According to GCHQ Director Iain Lobban, in a speech given at the University of Leeds on 4 October 2012: ‘In 1926, the Deputy Director of GC&CS, Edward Travis – who later became Director of GCHQ – went to Berlin and secured an Enigma machine by the simple expedient of going to the manufacturing company and buying one.’
5. Kendrick was a very talented cryptanalyst in his own right and he would go on to be a founder member of Hut 8 before spending the rest of the war in Ottawa, as GC&CS’s representative to the Canadian sigint organization.
6. TNA, HW43/1 Chapter VI, ‘Y’ Versus ‘Cryptography’, p. 184.
7. TNA, HW43/1 Chapt
er VI, ‘Y’ Versus ‘Cryptography’, p. 185.
8. TNA, HW 3/83 Post-War Notes by Josh Cooper, Head of AI 4(f), p. 27.
9. In April 2000 an Abwehr Enigma G312 was stolen from BP. Police divers duly searched the lake but no wartime crockery was found.
10. He told his friend and former intercept operator Diana Lucy many years later that as far as he knew at this stage, they could have been falling from the sky.
11. The log-readers would eventually move to BP in 1942 at Welchman’s instigation.
12. The Beaumanor Staff Magazine appeared from October 1941 until the end of the war. It was illustrated throughout by a distinguished cartoonist and full of poetry, essays, jokes and limericks, all presented with great wit and humour.
13. Perhaps even more remarkable is that while writing The Hut Six Story, Welchman did not have access to any documentation about the Polish methods. So in effect, he had to reinvent the idea of using perforated sheets (which became known as the Zygalski sheets or ‘Netz’ at BP) forty years later.
14. In correspondence with colleagues while researching his book, GW claimed that he did not feel slighted at all and was pleased that his idea had merit and was already under development. Furthermore, there was now a real chance that they would be able to read encrypted German messages.
15. It was hardly surprising that the Polish ambassador to Britain was outraged when the storyline of the 2001 film Enigma was revealed to him. Based on a novel by Robert Harris and set in BP, the plot describes how a cryptanalyst at BP is about to reveal its secrets to the Germans. His nationality – Polish! The Poles had been the first to work out the circuitry of the German military Enigma and read messages encrypted on it. Yet early accounts of the Enigma story by British and American authors mostly understated their pioneering work. Even Hinsley’s official history of British intelligence in the Second World War was inaccurate and incomplete on the subject. Today, a striking monument to that contribution stands at BP, fittingly, adjacent to ‘The Cottage’ where Knox and his team were able to exploit the technical breakthrough made by the Poles in the 1930s.