Max Newman and Tommy Flowers

Enigma cipher machine
Enigma cipher machine

WWII hindered the progress of computer inventors like Atanasoff and Zuse, but had the opposite effect on the first British steps toward the creation of an electronic computer. During the war, the Department of Communications of the British Foreign Office created machines, which used electronic circuits to assist the British in decoding intercepted German radio messages, coded with special machines. The English electronic computers were created by a group of people, with the leading role of the famous English mathematician Maxwell Newman and the engineer Thomas Flowers. Many others played important roles, including Alan Turing and C. E. Wynn-Williams.

The interception and decoding of German messages was a significant factor in the Allied victory, a fact kept secret until recently. The work was carried out in great secrecy at Government Code and Cipher School in Bletchley Park, GC&CS, a Victorian estate, situated some 80 km north of London. According to the historian Harry Hinsley, the work of crypto analysts in GC&CS was of great importance for the Allied victory and shortened the wartime by some two years.

The German army started using Enigma cipher machines (see the nearby photo) for the coding of military messages in 1925. Contrary to the beliefs of the Germans, the Enigma machine was not secure. In 1928, the Poles acquired knowledge about the German military Enigma by intercepting one, in customs, being sent to the German Embassy in Warsaw, and examining it. A whole series of Enigma machines were produced at the factory in Warsaw. A group of brilliant mathematics students at the Poznan university (Rejewski, Rozycki, and Zygalski) was recruited to work in the cryptological section of the Polish General Staff. In 1932, they decrypted the German Enigma signals. To facilitate decryption Rejewski designed an electromechanical programmable machine which he called Bomba (Polish for a bomb), because of the bomb-like ticking noise it made. In July 1939, the Poles gave the French and the British replicas of Polish-made Enigmas together with the drawings and information on the Enigma, Bomba, and the decryption information. Two mathematicians working at GC&CS, Alan Turing and Gordon Welchman, developed an improved version of the Bomb machine and over 200 of the Bombes were built by the British Tabulating Machine Company.

The British were very enthusiastic about the possibility to decode all the German military correspondence by means of the Bombs, but suddenly at the beginning of 1940, the interceptors started to catch German messages, coded with a different machine, which were impossible to be decoded. What happened?

Lorenz SZ42 cipher machine
Lorenz SZ42 cipher machine

At the end of the 1930s, the German Army High Command asked the company C. Lorenz AG to produce for them a high-security teleprinter cipher machine to enable them to communicate by radio in complete secrecy. The Lorenz AG designed the SZ40 and SZ42 cipher machines (see the nearby photo), based on the additive method for enciphering teleprinter messages invented in 1918 by Gilbert S. Vernam, of Brooklyn, New York (see the patent of Vernam). Since 1940 the Enigma machine was generally used by field units, the Lorenz machine was used for high-level communications (including Hitler’s orders) which could support the heavy machine, teletypewriter, and attendant fixed circuits. The Vernam system enciphered the message text by adding to it, character by character, a set of obscuring characters thus producing the enciphered text which was transmitted to the intended recipient. The simplicity of Vernam’s system was that if the obscuring characters were added in a rather special way (known as modulo 2 addition), then exactly the same obscuring characters added in the same way to the received enciphered message, canceled out the obscuring characters, and retrieved the original message. Vernam proposed that the obscuring characters should be completely random and pre-punched onto paper tape to be consumed character by character in synchronism with the input message characters. Such a cipher system using purely random obscuring characters is unbreakable.

The difficulty was, in a hot war situation, to make sure that the same random character tapes were available at each end of a communications link and that they were both set to the same start position. The Lorenz Company decided that it would be operationally easier to construct a machine to generate the obscuring character sequence. Because it was a machine, it could not generate a completely random sequence of characters. It generates what is known as a pseudo-random sequence. Unfortunately for the German Army, it was more pseudo than random and that was how it was broken. The amazing thing about SZ machines (in contrast with the Polish codebreakers’ success with the Enigma machine) is that the code breakers in GC&CS never saw an actual SZ machine until right at the end of the war, but they had been breaking the Lorenz cipher for two and a half years.

John Tiltman was one of the top code breakers in Bletchley Park and he took a particular interest in these enciphered teleprinter messages. They were given the code name fish and the messages which, as was later found out, were enciphered using the Lorenz machine were known as tunny. Tiltman knew of the Vernam system and soon identified these messages as being enciphered in the Vernam manner. Because the Vernam system depended on the addition of characters, Tiltman reasoned, if the operators had made a mistake and used the same Lorenz machine starts for two messages, then by adding the two cipher texts together character by character, the obscuring character sequence would disappear. And the British got a bit of fat—in August 1941 two German operators made a horrendous mistake, sending the same message 2 times (something absolutely forbidden by instructions), and a smart British interceptor catch both messages. Tiltman got the messages and for the first time succeeded to recover completely both texts. That was the breakthrough.

Then over the next two months, the Research section in GC&CS worked out the complete logical structure of the cipher machine. At the beginning of 1942, the Post Office Research Labs at Dollis Hill were asked to produce an implementation of the logic worked out by code breakers. Frank Morrell produced a rack of uniselectors and relays, which emulated the logic. It was called Tunny. So now when the manual code breakers in the Testery had laboriously worked out the settings used for a particular message, these settings could be plugged up on Tunny and the cipher text read in. If the code breakers had got it right, out came German. But it was taking four to six weeks to work out the settings. This meant that although they had proved that technically they could break Tunny, by the time the messages have been decoded the information in them was too stale to be operationally useful. The codebreakers deadly needed a faster machine.

The famous English mathematician Max Newman now came onto the scene. He thought that it would be possible to automate some parts of finding the settings used for each message, using electronic devices. He created a specification of a machine, which was built by the engineers at Dollis Hill. The logic was built by means of relays, but the counters are electronic, by the design of Charles Eryl Wynn-Williams (T. Flowers was also involved). The machine was called Heath Robinson after the cartoonist designer of fantastic machines.

Heath Robinson was delivered to GC&CS in June 1943. The machine compares two data flows, which are entered by means of two tape readers. The first tape contains the intercepted message, second—a probable decrypted message. Comparing continuously the two tapes and shifting the letters soon or later will decode the message, and the result will be printed on a typewriter. Heath Robinson presented some problems, however. The optical tape readers gave errors if a long stretch of adjacent holes or no holes occurred on the tapes. The major problem was keeping the two tapes in synchronization at over 1000 characters per second. Even a slight misalignment would render the whole process worthless. Heath Robinson however worked well enough to show that Max Newman’s concept was correct.

Newman then went to Dollis Hill, where he was put in touch with Thomas Flowers. Flowers was the brilliant Post Office electronics engineer who designed and built Colossus to meet Max Newman’s requirements for a machine to speed up the breaking of the Lorenz cipher. He had already given some advice on the building of Heath Robinson. Flower’s major contribution was to propose that the wheel patterns be generated electronically in ring circuits thus doing away with one paper tape and completely eliminating the synchronization problem. This required a vast number of electronic valves, but he was confident it could be made to work. He had, before the war, designed Post Office repeaters using valves. He knew that valves were reliable provided that they were never switched on and off. Nobody else believed him! Later Flowers will say: “My suggestion, made in February 1943, was met with considerable skepticism. The first reaction was that a machine with the number of tubes that was obviously going to be needed would be too unreliable to be useful. Fortunately, this criticism was defeated by the experience of the Post Office using thousands of tubes in its communication network. These tubes were not subject to movement or handling, and the power was never switched off. Under these conditions, tube failures were very rare.”

The Colossus of Bletchley Park in 1944
The Colossus of Bletchley Park in 1944

Colossus (called later Colossus Mark I) design started in March 1943. By December 1943 all the various circuits were working and the Colossus was dismantled shipped up to GC&CS and assembled. Colossus used state-of-the-art vacuum tubes (thermionic valves), thyratrons, and photomultipliers to optically read a paper tape and then applied a programmable logical function to every character, counting how often this function returned “true”. The computer (see the upper photo) was operational in January 1944 and successful on its first test against a real enciphered message tape. Colossus was able to read up to 5000 characters per second (cps), with the tape moving through it at about 50 km an hour, and reduced the time to break Lorenz messages from weeks to hours and just in time for messages to be deciphered which gave vital information to Eisenhower and Montgomery prior to D Day. These deciphered Lorenz messages showed that Hitler had swallowed the deception campaigns, the phantom army in the South of England, the phantom convoys moving east along the channel, that Hitler was convinced that the attacks were coming across the Pas de Calais and that he was keeping Panzer divisions in Belgium. After D-Day the French resistance and the British and American Air Forces bombed and strafed all the telephone and teleprinter land lines in Northern France, forcing the Germans to use radio communications and suddenly the volume of intercepted messages went up enormously.

In June 1944 was developed an improved version of Colossus Mark I, called Mark II, and eight more machines were quickly built to handle the increase in messages. The Mark I was upgraded to a Mark II, and there were thus ten Mark II Colossi in the GC&CS by the end of the war. By the end of hostilities 63 million characters of high-grade German messages had been decrypted. Mark II contained 2500 valves and 800 relays and was capable to read up to 25000 cps (five times faster than Mark I), due to the combination of parallel processing and buffer memory (registers), and contains a circuit for automatically changing the program when a probable code pattern was discovered.

Block diagram of Colossus
Block diagram of Colossus

Each of the ten Colossi occupied a large room in Bletchley Park. The racks were 2.3 m high of varying widths. There were eight racks arranged in two bays about 5.5 m long plus the paper tape reader and tape handler. The input of data was cipher text, punched onto 5-hole paper tape, and read at 5000 cps. The output was buffered onto relays and printed on a typewriter. The processor had a memory of 5 characters of 5-bits, held in a shift register, pluggable logic gates, and 20 decade counters arranged as 5 by 4 decades. The clock speed was 5 kHz, derived from sprocket holes in the input tape. Programming of the Colossus’ cross-correlation algorithm was achieved by a combination of telephone jack plugs, cords, and switches.

After Victory Day, suddenly it was all over. Eight of the ten Colossi were dismantled in Bletchley Park. Two went to London and were dismantled in about 1960 and in the same year all the drawings of Colossus were burnt, and of course, its very existence was kept secret. In the 1970s information began to emerge about Colossus. Professor Brian Randell of Newcastle University started researching the machine. Dr. Flowers and some of the other design engineers wrote papers in the 1980s describing Colossus in fairly general terms.

Colossus was the first of the electronic digital machines with programmability, albeit limited in modern terms. It was not, however, a fully general Turing-complete computer, even though Alan Turing worked at Bletchley Park, nor a stored program computer. It was not then realized that Turing completeness was significant; most of the other pioneering modern computing machines were also not Turing complete (e.g. the Atanasoff–Berry Computer, the Harvard Mark I electro-mechanical relay machine, the Bell Labs relay machines (by George Stibitz et al), or the first designs of Konrad Zuse). The notion of a computer as a general-purpose machine, that is, as more than a calculator devoted to solving difficult but specific problems, would not become prominent for several years.

Because of his parallel nature, Colossus is very fast, even by today’s standards. The intercepted message punched onto ordinary typewriter paper tape is read at 5000 characters per second. The sprocket holes down the middle of the tape are read to form the clock for the whole machine. This avoids any synchronization problems, whatever the speed of the tape, that’s the speed of Colossus. Tommy Flowers once wound up the paper tape drive motor to see what happened. At 9600 characters per second, the tape burst and flew all over the room at about 100 km/h! It was decided that 5000 cps was a safe speed. At 5000 cps the interval between sprocket holes is 200 microseconds. During this time Colossus will do up to 100 Boolean calculations simultaneously on each of the five tape channels and across a five-character matrix. The gate delay time is 1.2 microseconds which are quite remarkable for very ordinary valves. It demonstrates the design skills of Tommy Flowers.

The rebuilt Colossus
The rebuilt Colossus in 2007

In 1994, a team led by Tony Sale began a reconstruction of a Colossus at Bletchley Park. When the machine (see the nearby image) was ready, in November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for The National Museum of Computing, a contest was organized—the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode 3 messages enciphered using the Lorenz SZ42 and transmitted from radio station DL0HNF in the Heinz Nixdorf MuseumsForum computer museum. The challenge was easily won by radio amateur Joachim Schüth who had carefully prepared for the event and developed his own signal processing and decrypt code using the computer language Ada. The Colossus team was hampered by their wish to use World War II radio equipment, delaying them by a day because of poor reception conditions. Nevertheless, the victor’s 1.4 GHz laptop, running his own code, took less than a minute to find the settings for all 12 wheels. The German code breaker said: “My laptop digested ciphertext at a speed of 1.2 million characters per second—240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8 MHz for Colossus. That is a remarkable speed for a computer built in 1944.”

Biography of Max Newman and Tommy Flowers

Maxwell Newman (1897-1984)
Maxwell Newman (1897-1984)

The famous English mathematician Maxwell Newman was born Maxwell Hermann Alexander Neumann in Chelsea, London, England, on 7 February 1897. His father was the German Jewish immigrant Hermann Alexander Neumann, originally from the German city of Bromberg (now Bydgoszcz, Poland), who had emigrated with his family to London in 1881 at the age of 15. Hermann worked as a secretary in a company, and in 1896 married the 26-year-old Sarah Ann Pike, who was the daughter of a leather dresser, and came from a farming family, but had become a primary school teacher. Max was their only child.

The family moved to the London suburb of East Dulwich in 1903, and Max attended Goodrich Road school, then City of London School from 1908. As a schoolboy at the City of London School, Max demonstrated a great aptitude for classics and also mathematics where he was fortunate enough to come under the influence of a particularly stimulating teacher called F.W. Hill. Hill had formerly been a fellow at St. John’s College, Cambridge and it was to this college that Max in turn gained a scholarship, commencing his studies in 1915. Newman made a very promising start winning several prizes at the end of his first year and obtaining a First Class in Part 1 of the Mathematical Tripos. The next three years were spent away from Cambridge doing work related to the war. Initially, Newman took up teaching at Archbishop Holgate’s School in York.

After the outbreak of the First World War, this domestic tranquility as may have existed was shattered by the internment of Max’s father as an enemy alien. Hermann, who had lived in England for 33 of his 48 years was understandably disgusted at his treatment and returned to Germany immediately upon his release. Little detail is known of Max’s relationship with his father but in 1916, Max broke with the past and changed his surname by deed poll and was henceforward called Newman.

For national service, besides teaching at Archbishop Holgate’s Grammar School in York, Max worked in the Royal Army Pay Corps and taught at Chigwell School. He was called up for military service in February 1918, but claimed conscientious objection due to his beliefs and his father’s country of origin, and thereby avoided any direct role in the fighting.

His next challenge was to study for a college fellowship and in pursuit of this aim, Max spent 1922-3 in Vienna. The dissertation which Newman produced in 1923 in support of his fellowship contains some evidence of a nascent curiosity about the impact mechanized calculation might have on the mathematical sciences. Universal computing machines were still some way off, but Newman considers the use of “symbolic machines” for making predictions in physics. He was elected a fellow of St. John’s College in Cambridge in November 1923 and, in 1927, he was appointed as a lecturer in mathematics.

In 1934, Max much to the surprise of most of his friends announced his intention to marry. His bride-to-be was Lyn Lloyd Irvine, a writer, a friend of some years standing, and the daughter of a minister of the Church of Scotland. The wedding took place at the end of 1934 and, early the following year, the couple took up residence a few miles south of Cambridge at Cross Farm, Comberton. In the years that followed they had two sons, Edward (born 1935) and William (born 1939).

Over the next two decades, Newman applied himself to mathematics, setting out to tackle combinatorial topology, an area which, at that time no one else in Britain had attempted. Characteristically, his approach was to build on the work of the major pioneers in the field, proceeding incrementally in simple steps. The result was a collection of important papers and a number of theories that continue to be of interest to topologists. He also published papers on mathematical logic and solved a special case of Hilbert’s fifth problem. Namely, Newman was the reason, Alan Turing first encountered Hilbert’s, so-called Entscheidungsproblem (German for decision problem) around the Spring of 1935 when Turing was a student in Newman’s Part III Foundations of Mathematics course. In the middle of April 1936, Turing presented Newman with a draft of his breathtakingly original answer to the Entscheidungsproblem. At the heart of Turing’s paper was an idealized description of a person carrying out numerical computation which, following Alonzo Church, we have come to call a Turing machine. All modern computers are instantiations of Turing machines in consequence of which Turing’s paper is often claimed to be the single most important in the history of computing. From the moment Newman saw Turing’s solution he took him under his wing. Newman canvassed successfully for On Computable Numbers to be published by the London Mathematical Society and, simultaneously, enlisted Alonzo Church’s assistance in arranging for Turing to spend some time studying at Princeton.

Britain declared war on Germany on 3 September 1939. The part-Jewish ancestry of the Newman family was of particular concern in the face of Nazi Germany, and Lyn, Edward, and William were evacuated to America in July 1940. Newman remained at Cambridge, and at first continued research and lecturing. By the spring of 1942, he was considering involvement in war work. He made inquiries and was approached to work for the Government Code & Cipher School at Bletchley Park. He was cautious, concerned to ensure that the work would be sufficiently interesting and useful, and there was also the possibility that his father’s German nationality would rule out any involvement in top-secret work. The potential issues were resolved by the summer, and he agreed to arrive at Bletchley Park on 31 August 1942, where he became the main constructor of the English code-breaking machines Heath Robinson and Colossus.

After WWII Newman was appointed head of the Mathematics Department and the Fielden Chair of Pure Mathematics at the University of Manchester in 1945 and transformed it into a center of international renown. He obtained the support of the university and the Royal Society and assembled a first-rate team of mathematicians and engineers. Adopting exactly the same approach as he had used so effectively at Bletchley Park, Newman set his people loose on the detailed work while he concentrated on orchestrating the endeavor. By the middle of 1948, the SSEM (Small Scale Electronic Machine) was up and running, and although it was little more than a proof of concept it was still the world’s first working digital electronic stored-program computer.

Newman wrote Elements of the topology of plane sets of points, a definitive work on general topology. He also made major contributions to combinatorial topology. He was a laureate of many honors and awards, let’s mention only: Fellow of the Royal Society, Elected 1939; Royal Society Sylvester Medal, Awarded 1958; London Mathematical Society, President 1949-1951; LMS De Morgan Medal, Awarded 1962; Speaker International Congress of Mathematicians, 1962; D.Sc. University of Hull, Awarded 1968. The Newman Building at Manchester was named in his honor. The building housed the pure mathematicians from the Victoria University of Manchester between moving out of the Mathematics Tower in 2004 and July 2007 when the School of Mathematics moved into its new Alan Turing Building, where a lecture room is named in his honor.

Newman’s direct involvement with computing activity was, however, coming to an end. Newman was opposed to the inevitable use of the Manchester computer in the development of nuclear weapons and as the government took an ever closer interest in the Manchester computer, Max stepped back gradually, preferring to leave further development to the engineers. Newman was a deeply cultured man with an inquiring mind whose interests ranged over a broad canvas. His influence on the first generation of British computer scientists was incalculable, and his appreciation of the importance of computing long before it was generally apparent was probably matched only by that of Alan Turing. The vision and leadership which he showed at Bletchley Park during the Second World War and his single-minded determination to mechanize the British code-breaking efforts not only had an appreciable impact on the outcome of the conflict but created a computing legacy that he was determined to carry into the post-war situation. Such was the deftness by which he accomplished the transfer of knowledge that some of those who gained most from his understanding was more or less completely unaware of the singular contribution made to their own success by this remarkable man.

Newman retired in 1964 to live in Comberton, near Cambridge. After Lyn’s death in 1973, he married Margaret Penrose. This remarkable man died on 22 February 1984, in Cambridge.

Thomas Harold Flowers (1905-1998)
Thomas Harold Flowers (1905-1998)

Thomas Flowers was born at 160 Abbot Road, Poplar, in London’s East End on 22 December 1905, the son of a bricklayer. He seems to have been a practical child, when told of the arrival of a baby sister he declared a preference for a Meccano set (Meccano is a model construction kit comprising re-usable metal strips, plates, angle girders, wheels, axles, and gears, with nuts and bolts to connect the pieces. It enables the building of working models and mechanical devices). After school, he embarked on a four-year apprenticeship in Mechanical Engineering at the Woolwich Royal Arsenal and went to night classes to study successfully for a degree in Engineering from London University.

After graduation from London University in 1926, he joined the telecommunications branch of the General Post Office (GPO), which was then responsible for all telecommunications within the UK. In 1930 he moved to Dollis Hill in northwest London from 1930, the GPO’s research station, working on experimental electronic solutions for long-distance telephone systems. It was here that he began experiments with early electronic systems that would form the basis not only for Colossus, but also for advanced long-distance telephone systems, that developed into modern direct dialing. By 1939, he was convinced that an all-electronic system was possible, despite some problems with reliability. This background in switching electronics would prove crucial for his computer design in World War II.

In 1935, he married to Eileen Margeret Green and the couple later had two children, Kenneth and John.

After the war, Tommy Flowers returned to the Telephone Research Establishment at the GPO. He was awarded 1000 pounds for his war work, barely sufficient to pay off the debts that he had run up while developing Colossus. He was also honored with an MBE, thought now by some to be a scant reward for war-winning work. Although he proposed making a digital electronic exchange, he was not successful because he couldn’t convince the management of their worth nor tell them he had already worked on such systems. He remained there until 1964, then worked for International Telegraph and Telephone until his retirement in 1969. His work was not acknowledged until 1970 as he, and others, were bound by the Official Secrets Act to remain silent. All his family knew was that he was on some secret and important work.

Recognition came after the release of the Colossus information but much too late to give Tommy any real benefit. He received an honorary doctorate from Newcastle University in 1977, and another from De Montfort University in Leicester. Flowers received an honorary doctorate from Newcastle University in 1977, and another from Dc Montfort University in Leicester. More was planned. It became known that he was being considered for a knighthood, possibly in the New Years Honours List. Sadly, Tommy Flowers died from heart failure at home Mill Hill, London on 28 October 1998, at the age of 92.