| Methods and technology |
|---|
| Locations |
| Personnel |
Chief Gwido Langer German Section cryptologistsWiktor Michałowski Chief of Russian Section Jan Graliński Russian Section cryptologist Piotr Smoleński |
| The Enigma cipher machine |
|---|
 |
| Enigma machine |
| Breaking Enigma |
| Related |
TheCipher Bureau (Polish:Biuro Szyfrów,[ˈbʲurɔˈʂɨfruf]ⓘ) was theinterwarPolish General Staff'sSecond Department's unit charged withSIGINT and bothcryptography (theuse ofciphers andcodes) andcryptanalysis (thestudy of ciphers and codes, for the purpose of "breaking" them).
The precursor of the agency that would become the Cipher Bureau was created in May 1919, during thePolish-Soviet War (1919–1921), and played a vital role in securing Poland's survival and victory in that war.
In mid-1931, the Cipher Bureau was formed by the merger of pre-existing agencies. In December 1932, the Bureau began breakingGermany'sEnigmaciphers. Over the next seven years, Polish cryptologists overcame the growing structural and operating complexities of theplugboard-equipped Enigma. The Bureau also brokeSoviet cryptography.
Five weeks before the outbreak ofWorld War II, on 25 July 1939, inWarsaw, the Polish Cipher Bureau revealed its Enigma-decryption techniques and equipment to representatives of French and Britishmilitary intelligence, which had been unable to make any headway against Enigma. This Polish intelligence-and-technology transfer would give theAllies an unprecedented advantage (Ultra) in their ultimately victorious prosecution ofWorld War II.
On 8 May 1919 Lt.Józef Serafin Stanslicki established aPolish Army "Cipher Section" (Sekcja Szyfrów), precursor to the "Cipher Bureau" (Biuro Szyfrów).[1] The Cipher Section reported to thePolish General Staff and contributed substantially to Poland's defense byJózef Piłsudski's forces during thePolish-Soviet War of 1919–1921, thereby helping preserve Poland's independence, recently regained in the wake ofWorld War I.[2] TheCipher Section's purview included bothciphers andcodes.[3] InPolish the term "cipher" (szyfr) loosely refers toboth these two principal categories ofcryptography.[3] (Compare the opposite practice inEnglish, which loosely refers tobothcodes andciphers as "codes".[4])
During thePolish–Soviet War (1919–1921), approximately a hundred Russian ciphers were broken by a sizable cadre of Polish cryptologists who included army LieutenantJan Kowalewski and three world-famous professors of mathematics –Stefan Mazurkiewicz,Wacław Sierpiński, andStanisław Leśniewski.[5] Russian army staffs were still following the same disastrously ill-disciplined signals-security procedures as hadTsarist army staffs duringWorld War I, to the decisive advantage of their German enemy.[3] As a result, during the Polish-Soviet War the Polish military were regularly kept informed by Russian signals stations about the movements of Russian armies and their intentions and operational orders.[3]
The Soviet staffs, according to Polish Colonel Mieczysław Ścieżyński,
had not the slightest hesitation about sending any and all messages of an operational nature by means of radiotelegraphy; there were periods during the war when, for purposes of operational communications and for purposes of command by higher staffs, no other means of communication whatever were used, messages being transmitted either entirely "in clear" (plaintext) or encrypted by means of such an incredibly uncomplicated system that for our trained specialists reading the messages was child's play. The same held for the chitchat of personnel at radiotelegraphic stations, where discipline was disastrously lax.[6]
In the crucial month of August 1920 alone, Polish cryptologistsdecrypted 410 signals:
etc.[7]
The intercepts were as a ruledecrypted the same day, or at latest the next day, and were immediately sent to the PolishGeneral Staff's Section II (Intelligence) and operational section. The more important signals were read in their entirety by the Chief of the General Staff, and even by theCommander in Chief, MarshalJózef Piłsudski.[8] Interception and reading of the signals provided Polish intelligence with entire Russian operational orders. The Poles were able to follow the whole operation ofBudionny's Cavalry Army in the second half of August 1920 with incredible precision, just by monitoring his radiotelegraphic correspondence withTukhachevsky, including the famous and historic conflict between the two Russian commanders.[9]
The intercepts even included an order fromTrotsky to the revolutionary council of war of the Western Front, confirming Tukhachevsky's operational orders, thus giving them the authority of the supreme chief of the Soviet armed forces.[10] An entire operational order from Tukhachevsky to Budionny was intercepted on 19 August and read on 20 August, stating the tasks of all of Tukhachevsky's armies, of which only the essence had previously been known.[11]
Ścieżyński surmises that the Soviets must likewise have intercepted Polish operational signals; but he doubts that this would have availed them much, since Polish cryptography "stood abreast of modern cryptography" and since only a small number of Polish higher headquarters were equipped withradio stations, of which there was a great shortage; and finally, Polish headquarters were more cautious than the Russians and almost every Polishdivision had the use of aland line.[11]
Polish cryptologists enjoyed generous support under the command of Col.Tadeusz Schaetzel, chief of thePolish General Staff's Section II (Intelligence). They worked atWarsaw's radio stationWAR, one of two Polish long-range radio transmitters at the time. The Polish cryptologists' work led, among many other things, to the discovery of a large gap on theRed Army's left flank, which enabled Poland's MarshalJózef Piłsudski to drive a war-winning wedge into that gap during the August 1920Battle of Warsaw.[11]
The discovery of the Cipher Bureau's archives, decades after thePolish-Soviet War, has borne out Ścieżyński's assertion
that ... radio intelligence ... furnished [the Polish Commander-in-Chief,Józef Piłsudski], in the years 1919–1920 ... the most complete and... current intelligence on all aspects of the functioning of theRed Army, especially of units operating on the anti-Polish front, that it was radio intelligence that to a large degree determined the course of all ... military operations conducted by Poland in 1920 – from the January fighting atOvruch, through the March operation againstMozyr andKiev, the April operation inUkraine, the battles withTukhachevsky's first and second offensives inBelarus, the battles withBudionny's Cavalry Army, the Battle of Brody, to theBattles of Warsaw,Lwów and theNiemen.[11]
In mid-1931, at the PolishGeneral Staff, a Cipher Bureau was formed by merging the Radio-Intelligence Office (Referat Radiowywiadu) and the Polish-Cryptography Office (Referat Szyfrów Własnych).[12] The Bureau was charged with bothcryptography – the generation, and supervision of the use, ofciphers andcodes – andcryptology – the study of ciphers and codes, particularly for the purpose of breaking them.[13]
Between 1932 and 1936, the Cipher Bureau took on additional responsibilities, including radio communications betweenmilitary intelligence posts in Poland and abroad, as well as radiocounterintelligence – mobiledirection-finding and intercept stations for the locating andtraffic analysis ofspy andfifth column transmitters operating in Poland.[12]
In late 1927 or early 1928, there arrived at the Warsaw Customs Office from Germany a package that, according to the accompanying declaration, was supposed to contain radio equipment. The German firm's representative strenuously demanded that the package be returned to Germany even before going through customs, as it had been shipped with other equipment by mistake. His insistent demands alerted the customs officials, who notified the Polish General Staff's Cipher Bureau, which took a keen interest in new developments in radio technology. Since it happened to be a Saturday afternoon, the Bureau's experts had ample time to look into the matter. They carefully opened the box and found that it did not, in fact, contain radio equipment but a cipher machine. They examined the machine minutely, then put it back into the box.[14]
The Bureau's leading Enigma cryptanalystMarian Rejewski commented that the cipher machine may be surmised to have been acommercial-model Enigma since at that time the military model had not yet been devised. "Hence this trivial episode was of no practical importance, though it does fix the date at which the Cipher Bureau's interest in the Enigma machine began" – manifested, initially, in the entirely legal acquisition of a single commercial-model Enigma.[14]
On 15 July 1928, the first German machine-enciphered messages were broadcast by German military radio stations. Polish monitoring stations began intercepting them, and cryptologists in the Polish Cipher Bureau's German section were instructed to try to read them. The effort was fruitless, however, and was eventually abandoned. There remained very slight evidence of the effort, in the form of a few densely written-over sheets of paper and the commercial-model Enigma machine.[14] On 15 January 1929 MajorGwido Langer, after a tour of duty as chief of staff of the1st Legion Infantry Division, became chief of the Radio-Intelligence Office, and subsequently of the Cipher Bureau.[12] The Bureau's deputy chief, and the chief of its German section (BS-4), was CaptainMaksymilian Ciężki.
In 1929, while the Cipher Bureau's predecessor agency was still headed by Major Franciszek Pokorny (a relative of the outstandingWorld War IAustro-Hungarian Army cryptologist, CaptainHerman Pokorny[14]), Ciężki, Franciszek Pokorny, and a civilian Bureau associate,Antoni Palluth, taught a secretcryptology course atPoznań University for selected mathematics students. Over ten years later, duringWorld War II while inFrance, one of the students,Marian Rejewski, would discover that the entire course had been taught from French General Marcel Givièrge's book,Cours de cryptographie (Course of Cryptography), published in 1925.[15]
In September 1932, Maksymilian Ciężki hired three young graduates of the Poznań course to be Bureau staff members:Marian Rejewski,Jerzy Różycki andHenryk Zygalski.[15]
In 1926, the German Navy adopted, as its top cryptographic device, a modified civilianEnigma machine; in 1928 the German Army followed suit.[16] The complexity of the system was much increased in 1930 by the introduction of a plugboard (Steckerbrett), albeit with only six connecting leads in use.[17] In December 1932,Marian Rejewski made what historianDavid Kahn describes as one of the greatest advances in cryptologic history, by applying puremathematics – thetheory of permutations and groups – to breaking theGerman armed forces' Enigma machine ciphers.[18][19] Rejewski had worked out the precise interconnections of the Enigma rotors and reflector, after the Bureau had received, from French Military Intelligence CaptainGustave Bertrand, two German documents and two pages of Enigma daily keys (for September and October of that year).[20] These had been obtained by a Frenchmilitary intelligence agent, a German codenamedRex,[a] from an agent who worked at Germany's Cipher Office in Berlin,Hans-Thilo Schmidt, whom the French codenamedAsché.[b][21]
After Rejewski had worked out the military Enigma's logical structure, the Polish Cipher Bureau commissioned theAVA Radio Company, co-owned byAntoni Palluth, to build replicas ("doubles") of the Enigma to Rejewski's specifications.[22] His method of decrypting Enigma messages exploited two weaknesses of the German operating procedures.[c] It used what Rejewski called "characteristics" that were independent of the plugboard connections.[23] This involved compiling acard catalog of certain features of the set ofindicator settings.[24]
The Germans increased the difficulty of decrypting Enigma messages by decreasing the interval between changes in the order of the rotors from quarterly, initially, to monthly in February 1936, then daily in October of that year, when they also increased the number of plugboard leads from six to a number that varied between five and eight. This made the Biuro'sgrill method much less easy,[25] as it relied on 'unsteckered' letter pairs.[26] The German navy was more security-conscious than the army and air force, and in May 1937 it introduced a new, much more secure, indicator procedure that remained unbroken for several years.[27]
The next setback occurred in November 1937, when the scrambler's reflector was changed to one with different interconnections (known asUmkehrwalze-B). Rejewski worked out the wiring in the new reflector, but the catalogue of characteristics had to be compiled anew, again using Rejewski's "cyclometer", which had been built to his specifications by the AVA Radio Company.[28]
In January 1938, ColonelStefan Mayer directed that statistics be compiled for a two-week period, comparing the numbers of Enigma messages solved, to Enigma intercepts. The ratio came to 75 percent. "Nor",Marian Rejewski has commented, "were those 75 percent ... the limit of our possibilities. With slightly augmented personnel, we might have attained about 90 percent ... read. But a certain amount of cipher material ... due to faulty transmission or ... reception, or to various other causes, always remains unread".[29] Information obtained from Enigma decryption seems to have been directed from B.S.-4 principally to the German Office of the General Staff's Section II (Intelligence). There, from fall 1935 to mid-April 1939, it was worked up by MajorJan Leśniak, who in April 1939 would turn the German Office over to another officer and himself form a Situation Office intended for wartime service. He would head the Situation Office to and through theSeptember 1939 Campaign.[30]
The system of pre-defining the indicator setting for the day for all Enigma operators on a given network, on which the method of characteristics depended, was changed on 15 September 1938. The one exception to this was the network used by theSicherheitsdienst (SD)—the intelligence agency of theSS and theNazi Party—who did not make the change until 1 July 1939. Operators now chose their own indicator setting. However, the insecure procedure of sending the enciphered message key twice remained in use, and it was quickly exploited. Henryk Zygalski devised a manual method that used 26perforated sheets, and Marian Rejewski commissioned the AVA company to produce thebomba kryptologiczna (cryptologic bomb).[31]
Both the Zygalski-sheet method and eachbomba worked for only a single scrambler rotor order, so six sets of Zygalski sheets and sixbomby were produced.[32] However, the Germans introduced two new rotors on 15 December 1938, giving a choice of three out of five to assemble in the machines on a given day.[33] This increased the number of possible rotor orders from 6 to 60. The Biuro could then only read the small minority of messages that used neither of the two new rotors. They did not have the resources to produce 54 morebomby or 54 sets of Zygalski sheets. Fortunately, however, the fact that the SD network was still using the old method of the same indicator setting for all messages, allowed Rejewski to re-use his previous method of working out the wiring within these rotors.[34] This information was essential for the production of a full set Zygalski sheets which allowed resumption of large-scale decryption in January 1940. On 1 January 1939, the Germans made military Enigma even more difficult to break by increasing the number of plugboard connections from between five and eight, to between seven and ten.[26]
WhenWorld War II broke out on 1 September 1939, Leśniak and his colleagues had been working intensively for two or three years to establish the Germanorder of battle and had succeeded in working out nearly 95 percent of it. The German attack on Poland came as no surprise to thePolish General Staff. The results that had been obtained byPolish intelligence, according to Leśniak, "absolutely exceeded what would normally have been possible".[35]
| The Enigma cipher machine |
|---|
|
| Enigma machine |
| Breaking Enigma |
| Related |
Until 1937 the Cipher Bureau's German section,BS-4, had been housed in the Polish General Staff building – the stately 18th-century "Saxon Palace" – in Warsaw. That year BS-4 moved into specially constructed new facilities in theKabaty Woods nearPyry, south of Warsaw. There, working conditions were incomparably better than in the cramped quarters at the General Staff building.[36]
The move was dictated as well by requirements of security. Germany'sAbwehr was always looking for potential traitors among the military and civilian workers at the General Staff building. Strolling agents, even if lacking access to the Staff building, could observe personnel entering and leaving, and photograph them with concealed miniature cameras. AnnualAbwehr intelligence assignments for German agents in Warsaw placed a priority on securing informants at the Polish General Staff.[36]
It was in the Kabaty Woods, at Pyry, on 25 and 26[d] July 1939, with war looming, that, on instructions from the Polish General Staff, the Cipher Bureau's chiefs, Lt. Col.Gwido Langer and MajorMaksymilian Ciężki, the three civilian mathematician-cryptologists, and Col.Stefan Mayer, chief ofintelligence, revealed Poland's achievements to cryptanalytical representatives of France and Britain, explaining how they had broken Enigma. They undertook to give each country a Polish-reconstructed Enigma, along with details of their equipment, includingZygalski sheets and Rejewski'scryptologic bomb.[37] In return, the British pledged to prepare two full sets of Zygalski sheets for all 60 possible wheel orders.[38] The French contingent consisted of MajorGustave Bertrand, the French radio-intelligence and cryptology chief, and Capt.Henri Braquenié of the French Air Force staff. The British sent CommanderAlastair Denniston, head of Britain'sGovernment Code and Cypher School,Dilly Knox, chief Britishcryptanalyst[39] and Commander Humphrey Sandwith, head of theRoyal Navy's intercept anddirection-finding stations.[40]
When Rejewski had been working on reconstructing the German military Enigma machine in late 1932, he had ultimately solved a crucial element, the wiring of the letters of the alphabet into the entry drum, with the inspired guess that they might be wired in simplealphabetical order. Now, at the trilateral meeting – Rejewski was later to recount – "the first question that ...Dillwyn Knox asked was: 'What are the connections in the entry drum?'" Knox was mortified to learn how simple the answer was.[41]
The Poles' gift, to their western Allies, of Enigma decryption, five weeks before the outbreak of World War II, came not a moment too soon. FormerBletchley Park mathematician-cryptologistGordon Welchman later wrote: "Ultra would never have gotten off the ground if we had not learned from the Poles, in the nick of time, the details both of the German military ... Enigma machine, and of the operating procedures that were in use."[42] Allied Supreme CommanderDwight D. Eisenhower, at war's end, described intelligence from Bletchley Park as having been "of priceless value to me. It has simplified my task as a commander enormously." Eisenhower expressed his thanks for this "decisive contribution to the Allied war effort".[43]
British prime minister Winston Churchill's greatest wartime fear, even after Hitler had suspendedOperation Sea Lion andinvaded the Soviet Union, was that the German submarinewolfpacks would succeed in strangling sea-locked Britain.[44] A major factor that averted Britain's defeat in theBattle of the Atlantic was her regained mastery of Naval Enigma decryption; and while the latter benefited crucially from British seizure of German Enigma-equipped naval vessels, the breaking of German naval signals ultimately relied on techniques that had been pioneered by the Polish Cipher Bureau.[45] Had Britain capitulated to Hitler, the United States would have been deprived of an essential forward base for its subsequent involvement in the European andNorth African theaters.[46]
A week after the Pyry meeting,Dillwyn Knox, in a letter dated 1 August 1939, thanked the Poles, in Polish, "for your cooperation and patience". He enclosed little paper batons and a scarf picturing aDerby horse race – evidently emblematic of the cryptological race that Knox had hoped to win using the batons, and whose loss he was gallantly acknowledging.[47]
On 5 September 1939, as it became clear that Poland was unlikely to halt the ongoing German invasion, BS-4 received orders to destroy part of its files and evacuate essential personnel.[48]
During the GermanInvasion of Poland in September 1939, key Cipher Bureau personnel were evacuated southeast and – after the Soviets invaded eastern Poland on 17 September – into Romania, on the way destroying their cryptological equipment and documentation. Eventually, crossing Yugoslavia and still-neutral Italy, they reached France. Some personnel of the Cipher Bureau's German section who had worked with Enigma, and most of the workers at the AVA Radio Company that had builtEnigma doubles and cryptologic equipment for the German section, remained in Poland. Some were interrogated by theGestapo, but no one gave away the secret of Polish mastery of Enigma decryption.[50]AtPC Bruno, outsideParis, on 20 October 1939 the Poles resumed work on German Enigma ciphers in close collaboration with Britain'sGovernment Code and Cypher School atBletchley Park.[51]
In the interest of security, the Allied cryptological services, before sending their messages over ateleprinter line, encrypted them usingEnigma doubles.Henri Braquenié often closed messages with a"Heil Hitler!".[52] As late as December 1939, when Lt. Col.Gwido Langer, accompanied by CaptainBraquenié, visited London and Bletchley Park, the British asked that the Polish cryptologists be turned over to them. Langer, however, took the position that the Polish team must remain where thePolish Armed Forces were being formed – onFrench soil.[53] The mathematicians might actually have reached Britain much earlier – and much more comfortably – than they eventually did; but in September 1939, when they went to the British embassy inBucharest, Romania, they were brushed off by a preoccupied British diplomat.[54]
In January 1940, the British cryptanalystAlan Turing spent several days at PC Bruno conferring with his Polish colleagues. He had brought the Poles a full set ofZygalski sheets that had been produced at Bletchley Park byJohn Jeffreys using Polish-supplied information. On 17 January 1940, the Poles made the first break into wartime Enigma traffic – that from 28 October 1939.[55]
During this period, until the collapse of France in June 1940, ultimately 83 percent of the Enigma keys that were found, were solved at Bletchley Park, the remaining 17 percent at PC Bruno. Rejewski commented:
How could it be otherwise, when there were three of us [Polish cryptologists] and [there were] at least several hundred British cryptologists, since about 10,000 people worked in Bletchley ... Besides, recovery of keys also depended on the amount of intercepted cipher material, and that amount was far greater on the British side than on the French side. Finally, in France (by contrast with the work in Poland) we ourselves not only sought for the daily keys, but after finding the key also read the messages. ... One can only be surprised that the Poles had as many as 17 percent of the keys to their credit.[56][57][e]
.jpg)
The inter-Allied cryptologic collaboration prevented duplication of effort and facilitated discoveries. Before fighting had started inNorway in April 1940, the Polish-French team solved an uncommonly hard three-lettercode used by the Germans to communicate with fighter and bomber squadrons and for exchange of meteorological data between aircraft and land.[58] The code had first appeared in December 1939, but the Polish cryptologists had been too preoccupied with Enigma to give the code much attention.[58] With the German assault on the west impending, however, the breaking of theLuftwaffe code took on mounting urgency. The trail of the elusive code (whose system of letters changed every 24 hours) led back to Enigma. The first clue came from the British, who had noticed that the code's letters did not change randomly. IfA changed toP, then elsewhereP was replaced byA. The British made no further headway, but the Poles realized that what was manifesting was Enigma'sexclusivity principle that they had discovered in 1932. The Germans' carelessness meant that now the Poles, having after midnight solved Enigma's daily setting, could with no further effort also read theLuftwaffe signals.[59][f]
The Germans, just before opening their 10 May 1940 offensive in the west that would trampleBelgium,Luxembourg and theNetherlands in order to reach the borders of France, once again changed their procedure for enciphering message keys, rendering the Zygalski sheets "completely useless"[60][61] and temporarily defeating the joint British–Polish cryptologic attacks on Enigma. According toGustave Bertrand, "It tooksuperhuman day-and-night effort to overcome this new difficulty: on May 20, decryption resumed."[62][g]
Following the capitulation of France in June 1940, the Poles were evacuated toAlgeria. On October 1, 1940, they resumed work atCadix, nearUzès in unoccupied southernVichy France, under the sponsorship of Gustave Bertrand.[63]
A little over two years later, on 8 November 1942, Bertrand learned from theBBC that the Allies had landed inFrench North Africa ("Operation Torch"). Knowing that in such an eventuality the Germans planned to occupyVichy France, on 9 November he evacuatedCadix. Two days later, on 11 November, the Germans indeed marched into southern France. On the morning of 12 November they occupied Cadix.[64]
Over the two years since its establishment in October 1940, Cadix had decrypted thousands ofWehrmacht,SS andGestapo messages, originating not only from French territory but from across Europe, which provided invaluable intelligence to Allied commands andresistance movements.[65][h] Cadix had also decrypted thousands ofSoviet messages.[66]
Having departed Cadix, the Polish personnel evaded the occupying Italian security police and GermanGestapo and sought to escape France viaSpain.[67]Jerzy Różycki,Jan Graliński andPiotr Smoleński had died in the January 1942 sinking, in theMediterranean Sea, of a French passenger ship, theSS Lamoricière, in which they had been returning to southern France from a tour of duty inAlgeria.[i][68]
Marian Rejewski andHenryk Zygalski hiked over thePyrenees with a guide (who robbed them at gunpoint) to the Spanish border, where they were arrested on 30 January 1943.[69] They were incarcerated by the Spaniards for three months before being released, uponRed Cross intervention, on 4 May 1943.[70] They then managed, by a circuitous land–sea–air route, to join thePolish Armed Forces in Britain,[71] Rejewski and Zygalski were inducted into the Polish Army as privates (they would eventually be promoted to lieutenant) and put to work breaking GermanSS andSD hand ciphers at a Polish signals facility inBoxmoor. Because of their having been in occupied France, the British considered it too risky to invite them to work at Bletchley Park.[72]
Finally, with the end of the two mathematicians' cryptologic work at the close of World War II, the Cipher Bureau ceased to exist. From nearly its inception in 1931 until war's end in 1945, the Bureau, sometimes incorporated into aggregates undercryptonyms (PC Bruno and Cadix), had been essentially the same agency, with most of the same core personnel, carrying out much the same tasks; now it was extinguished. Neither Rejewski nor Zygalski would work again as cryptologists.[73] In late 1946 Rejewski returned to his family in a devastated and politically altered Poland, to live there another 33 years until his death in February 1980.[74] Zygalski would remain in England until his death in August 1978.[73]
Despite their travails, Rejewski and Zygalski had fared better than some of their colleagues. Cadix's Polish military chiefs,Langer andCiężki, had also been captured—by the Germans, as they tried to escape from France into Spain on the night of 10–11 March 1943—along with three other Poles:Antoni Palluth,Edward Fokczyński and Kazimierz Gaca.[75] The first two becameprisoners of war; the other three were sent asslave labourers to Germany, where Palluth and Fokczyński perished.[76] Despite the varyingly dire circumstances in which they were held, none of them—Stefan Mayer emphasizes—betrayed the secret of Enigma'sdecryption, thus making it possible for the Allies to continue exploiting this vital intelligence resource.[77]
Before the war,Palluth, a lecturer in the 1929 secretPoznań Universitycryptology course, had been co-owner of AVA, which produced equipment for the Cipher Bureau, and knew many details of the decryption technology.[78] In Warsaw, under German occupation, other Cipher Bureau workers were interrogated by German intelligence commissions, and some AVA workers were approached by German agents, but all kept silent about compromises to Enigma.[79]
In 1967 the Polish military historianWładysław Kozaczuk, in his bookBitwa o tajemnice (The Battle for Secrets), first revealed that the German Enigma had been broken by Polish cryptologists before World War II. Kozaczuk's disclosure came seven years beforeF. W. Winterbotham'sThe Ultra Secret (1974) changed conventional views of the history of the war.[80]
The 1979 Polish filmSekret Enigmy (The Enigma Secret)[81][better source needed] is a generally fair, if superficial, account of the Cipher Bureau's story.[citation needed] Twenty-two years later, the 2001 Hollywood filmEnigma was criticized for its many historical inaccuracies, including omission of Poland's fundamental work in Enigmadecryption.[82]
