RT Journal Article T1 Zygalski sheets: Polish codebreaking and the role of reconstruction in the Top Secret exhibition at the Science Museum A1 Elizabeth Bruton A1 Jeremy McCarthy A1 Dermot Turing YR 2022 VO IS Spring 2022 AB The Top Secret: From ciphers to cyber security exhibition at various Science Museum Group sites from 2019 to 2022 explored the remarkable, little-known world of codebreaking, ciphers and secret communications from the trenches of the First World War to cyber security today. At the heart of the exhibition was the personal and technological story of codebreaking at Bletchley Park, the British centre for codebreaking and cryptanalysis during the Second World War, as well an acknowledgement of the vital pre-war contribution of the Polish Cipher Bureau. Zygalski sheets, developed by Polish codebreaker and mathematician Henryk Zygalski in 1938, were a manual grid-based cardboard system used by the Polish Cipher Bureau and Bletchley Park to aid the decryption of German Enigma machine cipher messages. Lacking original artefacts and visual historical representation thereof, the Top Secret curator Dr Elizabeth Bruton turned to external experts on the Polish cipher bureau and codebreaking in the Second World War, Dr Dermot Turing (writer) and Jeremy McCarthy (volunteer at The National Museum of Computing (TNMOC)). The ensuing email conversation explored how the design and use of the Zygalski sheets could be reconstructed from the existing and sometimes contradictory evidence and sources. This conversation offers a rare insight into the research process and expert peer review behind an exhibition object and label. Secondly, we offer a reflection on museum practice, exploring how the resulting reconstruction was interpreted and displayed within the Top Secret exhibition alongside authentic historic artefacts from the Science Museum Group’s and GCHQ’s historic collections. NO For histories of GCHQ, see: Aldrich, R, 2010, GCHQ: The Uncensored Story of Britain’s Most Secret Intelligence Agency (London: Harper Press); Ferris, J, 2020, Behind the Enigma: the authorised history of GCHQ, Britain's secret cyber-intelligence agency (London: Bloomsbury); Varghese, S, 2019, ‘GCHQ’s centenary: the art of espionage in a digital age’, New Statesman, https://www.newstatesman.com/science-tech/privacy/2019/07/gchq-s-centenary-art-espionage-digital-age (accessed 1 January 2021); and West, N, 1987, GCHQ: The Secret Wireless War, 1900–1986 (London: Hodder and Stoughton). NO For histories of Bletchley Park, see Copeland, B J (ed), 2006, Colossus: the secrets of Bletchley Park's codebreaking computers (Oxford: Oxford University Press); Dunlop, T, 2015, The Bletchley girls: war, secrecy, love and loss: the women of Bletchley Park tell their story (London: Hodder & Stoughton); Kenyon, D, 2019, Bletchley Park and D-Day: the untold story of how the battle for Normandy was won (New Haven; London: Yale University Press); Smith, M, 1998, Station X: the codebreakers of Bletchley Park (London: Channel 4 Books); and Turing, D, 2020, The Codebreakers of Bletchley Park: The Secret Intelligence Station that Helped Defeat the Nazis (London: Arcturus Publishing). NO For histories of Polish codebreaking in the 1930s and Second World War, see: Bloch, G, 2001, ‘Polish Reconstitution of the German Military Enigma and the First Decryptments of Its Messages’, Journal of Intelligence History 1:1, 36–44, DOI: https://doi.org/10.1080/16161262.2001.10555045 (accessed 2 September 2021); Ciechanowski, J S (ed), 2005, Living with the Enigma Secret: Marian Rejewski 1905–1980 (Bydgoszcz, Poland: Bydgoszcz City Council); Kozaczuk, W (ed) and C Kasparek (trans), 1984, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two (Frederick, MD: University Publications of America); Mayer, S, 1974, The Breaking up of the German Ciphering Machine "Enigma" by the Cryptological Section in the 2nd Department of the Polish Armed Forces General Staff (New York: Piłsudski Institute); Rejewski, M, 1981, ‘How the Polish Mathematicians Deciphered the Enigma’, Annals of the History of Computing, 3/3, 213-234; Turing, D, 2018, X, Y & Z: the real story of how Enigma was broken (Stroud: The History Press); and Welchman, G, 1986, ‘From Polish Bomba to British Bombe: The birth of ultra’, Intelligence and National Security, 1:1, 71–110, DOI: https://doi.org/10.1080/02684528608431842 (accessed 2 September 2021). NO See Christensen, C, 2007, ‘Polish Mathematicians Finding Patterns in Enigma Messages’, Mathematics Magazine, 80(4), 247–273 http://www.jstor.org/stable/27643040 (accessed 3 September 2021). For further information on the ‘Enigma Relay’ and Polish-Anglo-French co-operation around breaking Enigma, see Józef Piłsudski Institute: Enigma Relay news items, https://www.pilsudski.org.uk/en/aktualnosci.php?wid=22 (accessed 2 August 2021); Polish Embassy US Medium.com: Enigma Relay: The Anglo-French-Polish Effort to Break the Enigma during World War II, https://medium.com/@PolishEmbassyUS/enigma-relay-the-anglo-french-polish-effort-to-break-the-enigma-during-world-war-ii-c896b7968a35 (accessed 2 August 2021); and Bruton, E, 2020, Science Museum blog: Breaking Enigma: A story of European co-operation, https://blog.sciencemuseum.org.uk/breaking-enigma-a-story-of-european-co-operation/ (accessed 2 August 2021). NO For further information on Zygalski, see Kapera, Z I, 2015, The triumph of Zygalski's sheets: the Polish Enigma in the early 1940 (Mogilany: Enigma Press) and O'Connor, J J and Robertson, E F (last updated 2017), MacTutor History of Mathematics Archive: Henryk Michał Zygalski, https://mathshistory.st-andrews.ac.uk/Biographies/Zygalski/ (accessed 1 October 2021). NO Computer History Museum object number 102652257, image of decryption sheets similar to Zygalski sheets used to decipher Enigma at https://www.computerhistory.org/collections/catalog/102652257 (accessed 20 January 2022) and Demonstration of Zygalski sheets (perforated sheets) at Bletchley Park, photographed by Toby Oxborrow, taken on 11 September 2004 at https://www.flickr.com/photos/oxborrow/37527502/in/set-828575/ and archived at https://commons.wikimedia.org/wiki/File:Zygalski_sheets_(perforated_sheets).jpg (accessed 20 January 2022). NO In order of publication, key early examples are: Woytak, R A, 1978, ‘The origins of the Ultra-Secret code in Poland, 1937–1938’, The Polish Review, 23:3 79–85, http://www.jstor.org/stable/25777589 (accessed 17 February 2022); Kahn, D, 1978, ‘Le rôle du décryptage et du renseignement dans la stratégie et la tactique des Alliés’, Revue d’histoire de La Deuxième Guerre Mondiale, 28:111, 73–85, http://www.jstor.org/stable/25728928 (accessed 17 February 2022); Kozaczuk, W, 1979, W kręgu Enigmy [In the Circle of Enigma] (Warsaw: Wydawnictwo Książka i Wiedza); Calvocoressi, P, 1980, Top Secret Ultra (New York: Pantheon Books); Garliński, J, 1980, The Enigma War (New York: Scribner) [published in Polish as Garliński, J, 1980, Enigma. Tajemnica drugiej wojny swiatowej (London: Odnowa)]; Rejewski, M, 1980, ‘An Application of the Theory of Permutations in Breaking the Enigma Cipher’, Applicationes Mathematicae, 16:4, 543–559, DOI: https://doi.org/10.4064%2Fam-16-4-543-559 (accessed 1 October 2021); Rejewski, M and J Stepenske (trans), 1981, ‘How Polish Mathematicians Deciphered the Enigma’, Annals of the History of Computing 3, no. 3: 214–234. DOI: https://doi.org/10.1109/MAHC.1981.10033 (accessed 1 October 2021) and Rejewski, M and J Stepenske (trans), 1982, ‘Mathematical Solution of the Enigma Cipher’, Cryptologia, 6:1, 1–18, DOI: https://doi.org/10.1080/0161-118291856731 (accessed 1 October 2021); Rejewski, M and C Kasparek 1982, 'Remarks on Appendix 1 to British Intelligence in the Second World War by F H Hinsley’, Cryptologia, 6:1, 75–83, DOI: https://doi.org/10.1080%2F0161-118291856867 (accessed 1 October 2021); and Kozaczuk, W, 1984, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two (Frederick, Md.: University Publications of America), the expanded, English-language version of Kozaczuk’s 1979 Polish-language W kręgu Enigmy. NO See Atkins, L J, Velez, L, Goudy, D and Dunbar, K N, 2009, ‘The unintended effects of interactive objects and labels in the science museum’, Science Education 93:1, 161–184, https://doi.org/10.1002/sce.20291 (accessed 1 January 2022); Fragomeni, D, 2010, ‘The Evolution of Exhibit Labels’, Faculty of Information Quarterly, 2:1, 1–11, https://hdl.handle.net/1807/80213 (accessed 1 January 2022); and Hohenstein, J and Tran, L U, 2007, ‘Use of Questions in Exhibit Labels to Generate Explanatory Conversation among Science Museum Visitors’, International Journal of Science Education, 29:12, 1557–1580, DOI: https://doi.org/10.1080/09500690701494068 (accessed 1 January 2022). NO For details of John Ferris’ comments about Bletchley Park in 2020, see Beach, J, 2020, History at Northampton: Collision report: Bletchley Park, Folklore, and Academic History, https://historyatnorthampton.com/2021/01/13/collision-report-bletchley-park-folklore-and-academic-history/ (accessed 1 October 2021); Corera, G, 2020, BBC News: Bletchley Park’s contribution to WW2 ‘over-rated’, https://www.bbc.com/news/uk-54604895 (accessed 1 October 2021); and Panagopoulos, E, 2020, “Overrated” : Historic fact and fiction in the age of social media, https://battleofbritainhouse.org/2020/10/20/overrated-historic-fact-and-fiction-in-the-age-of-social-media/ (accessed 1 October 2021). NO See TNA HW 25/12 ‘ENIGMA history. Papers relating to the pre-war meetings between French and Polish cryptanalysts and members of GC & CS on the subject of ENIGMA; subsequent wartime correspondence between KNOX and DENNISTON on ENIGMA processing at Bletchley Park’, September 1938–June 1943, which includes correspondence between Dilly Knox in Warsaw, Poland and Alastair Denniston at Bletchley Park about the Polish revelations about breaking Enigma to their British and French allies in July 1939. For secondary sources on the July 1939 meeting near Warsaw, see: Erskine, R, 2006, ‘The Poles Reveal their Secrets: Alastair Denniston’s Account of the July 1939 Meeting at Pyry’, Cryptologia, 30:4, 294–305, DOI: https://doi.org/10.1080/01611190600920944 (accessed 1 October 2021) and Gallehawk, J, 2006, ‘Third Person Singular (Warsaw, 1939)’, Cryptologia, 30:3, 193–198, DOI: https://doi.org/10.1080/01611190600612129. NO See Rejewski, M and J Stepenske (trans), 1981, ‘How Polish Mathematicians Deciphered the Enigma’, Annals of the History of Computing 3, no. 3: 214–234. DOI: https://doi.org/10.1109/MAHC.1981.10033 (accessed 1 October 2021) and Rejewski, M and J Stepenske (trans), 1982, ‘Mathematical Solution of the Enigma Cipher’, Cryptologia, 6:1, 1–18, DOI: https://doi.org/10.1080/0161-118291856731 (accessed 1 October 2021). NO For further information on Zygalski, see Kapera, Z I, 2015, The triumph of Zygalski's sheets: the Polish Enigma in the early 1940 (Mogilany: Enigma Press) and O'Connor, J J and Robertson, E F (last updated 2017), MacTutor History of Mathematics Archive: Henryk Michał Zygalski, https://mathshistory.st-andrews.ac.uk/Biographies/Zygalski/ (accessed 1 October 2021). NO Rejewski, M, 1980, ‘An Application of the Theory of Permutations in Breaking the Enigma Cipher’, Applicationes Mathematicae, 16:4, 543–559, DOI: https://doi.org/10.4064%2Fam-16-4-543-559(accessed 1 October 2021); Rejewski, M and J Stepenske (trans), 1982, ‘Mathematical Solution of the Enigma Cipher’, Cryptologia, 6:1, 1–18, DOI: https://doi.org/10.1080/0161-118291856731 (accessed 1 October 2021); and Garliński, J, 1980, The Enigma war (New York: Scribner), 40 NO For a brief overview of the history of changing museum display practices in British museums, see Kistler, J and Tattersdill, W, 2019, ‘What’s your dinosaur? Or, imaginative reconstruction and absolute truth in the museum space’, Museum and Society, 17:3, 377–389. DOI: https://doi.org/10.29311/mas.v17i3.3219 (accessed 1 January 2022). NO For discussions around interpretation, museum authority, visitor experience and the contested and controversial concept of authenticity, see, for example: Gordon, R, Hermens, E and Lennard, F (eds), 2014, Authenticity and Replication: The 'Real Thing' in Art and Conservation (London: Archetype Publications); Kidd, J, 2011, ‘Performing the knowing archive: heritage performance and authenticity’, International Journal of Heritage Studies, 17:1, 22–35, DOI: https://doi.org/10.1080/13527258.2011.524003 (accessed 31 October 2021); Schwan, S and Dutz, S, 2020, ‘How do Visitors Perceive the Role of Authentic Objects in Museums?’, Curator, 63: 217–237. https://doi.org/10.1111/cura.12365 (accessed 31 October 2021); and Thompson, C, 1994, ‘The role of the museum in interpretation: The problem of context’, International Journal of Heritage Studies, 1:1, 40–51, DOI: https://doi.org/10.1080/13527259408722129 (accessed 31 October 2021). NO For further information about Christopher Baker’s Murmur Study artwork, see Baker, C, 2009, Christopher Baker: Murmur Study, a live Twitter visualisation and archive, http://christopherbaker.net/projects/murmur-study/ (accessed 31 October 2021). NO The Science Museum, London and its predecessors have displayed reproductions, including scale models, since its foundation as the South Kensington Museum in 1857. See Morris, P J T (ed), 2010, Science for the Nation: Perspectives on the History of the Science Museum (London: ‎ Palgrave Macmillan). I also discussed this with Science Museum Curator Emeritus John Liffen via email in late November 2020. NO See Kidd, J, 2011, ‘Performing the knowing archive: heritage performance and authenticity’, International Journal of Heritage Studies, 17:1, 22–35, DOI: https://doi.org/10.1080/13527258.2011.524003 (accessed 31 October 2021) and Thompson, C, 1994, ‘The role of the museum in interpretation: The problem of context’, International Journal of Heritage Studies, 1:1, 40–51, DOI: https://doi.org/10.1080/13527259408722129 (accessed 31 October 2021) PB The Science Museum Group SN 2054-5770 LA eng DO 10.15180/221702 UL https://journal.sciencemuseum.ac.uk/article/zygalski-sheets-polish-codebreaking-and-the-role-of-reconstruction-in-the-top-secret-exhibition-at-the-science-museum/ WT Science Museum Group Journal OL 30