Working replica Heath Robinson machine at The National Museum of Computing on Bletchley Park. On the right is the paper tape transport mechanism that was dubbed the "bedstead" because of a resemblance to an upended metal bed-frame.
The functional specification of the machine was produced by Max Newman. The main engineering design was the work of Frank Morrell[4] at the Post Office Research Station at Dollis Hill in North London, with his colleague Tommy Flowers designing the "Combining Unit".[5] Dr C. E. Wynn-Williams from the Telecommunications Research Establishment at Malvern produced the high-speed electronic valve and relay counters.[5] Construction started in January 1943,[6] the prototype machine was delivered to Bletchley Park in June and was first used to help read current encrypted traffic soon afterwards.[7]
As the Robinson was a bit slow and unreliable, it was later replaced by the Colossus computer for many purposes, including the methods used against the twelve-rotor Lorenz SZ42 on-line teleprinter cipher machine (code named Tunny, for tunafish).[8][9]
Tutte's statistical method
The basis of the method that the Heath Robinson machine implemented was Bill Tutte's"1+2 technique".[10] This involved examining the first two of the five impulses[11] of the characters of the message on the ciphertext tape and combining them with the first two impulses of part of the key as generated by the wheels of the Lorenz machine. This involved reading two long loops of paper tape, one containing the ciphertext and the other the component of the key. By making the key tape one character longer than the message tape, each of the 1271 starting position of the 12 sequence was tried against the message.[12] A count was amassed for each start position and, if it exceeded a pre-defined "set total", was printed out. The highest count was the most likely one to be the one with the correct values of 1 and 2. With these values, settings of the other wheels could be tried to break all five wheel starting positions for this message. This then allowed the effect of the component of the key to be removed and the resulting modified message attacked by manual methods in the Testery.
Tape transport
The "bedstead" was a system of pulleys around which two continuous loops of tape were driven in synchrony. Initially this was by means of a pair of sprocket wheels on a common axle. This was changed to drive by friction pulleys with the sprocket wheels maintaining the synchrony when it was found that this caused less damage to the tapes. Speeds of up to 2000 characters per second were achieved for shorter tapes, but only 1000 for longer tapes. The tapes were guided past an array of photo-electric cells where the characters and other signals were read.[13] Possible tape lengths on the bedstead were from 2000 to 11,000 characters.[14]
Tape reading
The perforated tapes were read photo-electrically at a "gate" which was placed as near as possible to the sprocket to reduce the effect of stretched tapes. Successive characters on the tape were read by a battery of ten photocells, an eleventh for the sprocket holes and two additional ones for the "stop" and "start" signals that were hand-punched between the third and fourth and fourth and fifth channels.[13]
Combining unit
This was designed by Tommy Flowers of the Post Office Research Station at Dollis Hill in North London.[5] It used thermionic valves (vacuum tubes) to implement the logic. This involved the Boolean"exclusive or" (XOR) function in combining the various bit-streams. In the following "truth table", 1 represents "true" and 0 represents "false". (At Bletchley Park these were known as x and • respectively.)
INPUT
OUTPUT
A
B
A ⊕ B
0
0
0
0
1
1
1
0
1
1
1
0
Other names for this function are: "not equal" (NEQ), "modulo 2 addition" (without carry) and "modulo 2 subtraction" (without 'borrow'). Note that modulo 2 addition and subtraction are identical. Some descriptions of Tunny decryption refer to addition and some to differencing, i.e. subtraction, but they mean the same thing.
The combining unit implemented the logic of Tutte's statistical method. This required that the paper tape containing the ciphertext was tried against a tape that contained the component of the Lorenz cipher machine generated by the relevant two chi wheels at all possible starting positions. A count was then made of the total number of 0s generated, with a high count indicating a greater probability of the starting position of the chi key sequence being correct.
Counting
Wynn-Williams had obtained his PhD at Cambridge University for his work at the Cavendish Laboratory with Sir Ernest Rutherford.[15] In 1926 he had constructed an amplifier using thermionic valves (vacuum tubes) for the very small electrical currents arising from detectors in their nuclear disintegration experiments. Rutherford had got him to devote his attention to the construction of a reliable valve amplifier and methods of registering and counting these particles. The counter used gas-filled Thyratron tubes which are bi-stable devices.
The counters that Wynn-Williams designed for Heath Robinson, and subsequently for the Colossus computers used thyratrons to count units of 1, 2, 4, 8; high speed relays to count units of 16, 32, 48, 64; and slower relays to count 80, 160, 240, 320, 400, 800, 1200, 1600, 2000, 4000, 6000, and 8000.[14] The count obtained for each run-through of the message tape was compared with a pre-set value, and if it exceeded it, was displayed along with a count that indicated the position of the key tape in relation to the message tape. The Wren operators initially had to write down these numbers before the next count that exceeded the threshold was displayed – which was "a fruitful source of error",[16] so a printer was soon introduced.
Robinson developments
The original Heath Robinson was a prototype and was effective despite a number of serious shortcomings.[16] All but one of these, the lack of "spanning"[17] ability, were progressively overcome in the development of what became known as "Old Robinson".[18] However, Tommy Flowers realised that he could produce a machine that generated the key stream electronically so that the main problem of keeping two tapes synchronised with each other would be eliminated. This was the genesis of the Colossus computer.
Despite the success of Colossus, the Robinson approach was still valuable for certain problems. Improved versions were developed, nicknamed Peter Robinson and Robinson and Cleaver after department stores in London.[19] A further development of the ideas was a machine called Super Robinson or Super Rob.[20] Designed by Tommy Flowers, this one had four bedsteads[21] to allow for running four tapes and was used for running depths and "cribs" or known-plaintext attack runs.[22][23]
↑ Spanning was the ability to limit consideration of the message tape to a defined section (or "span") in a situation in which it was known or suspected that there was an error in a particular part of the tape.
Bletchley Park is an English country house and estate in Bletchley, Milton Keynes (Buckinghamshire), that became the principal centre of Allied code-breaking during the Second World War. The mansion was constructed during the years following 1883 for the financier and politician Herbert Leon in the Victorian Gothic, Tudor and Dutch Baroque styles, on the site of older buildings of the same name.
Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves to perform Boolean and counting operations. Colossus is thus regarded as the world's first programmable, electronic, digital computer, although it was programmed by switches and plugs and not by a stored program.
Maxwell Herman Alexander Newman, FRS, generally known as Max Newman, was a British mathematician and codebreaker. His work in World War II led to the construction of Colossus, the world's first operational, programmable electronic computer, and he established the Royal Society Computing Machine Laboratory at the University of Manchester, which produced the world's first working, stored-program electronic computer in 1948, the Manchester Baby.
William Thomas Tutte was an English and Canadian code breaker and mathematician. During the Second World War, he made a brilliant and fundamental advance in cryptanalysis of the Lorenz cipher, a major Nazi German cipher system which was used for top-secret communications within the Wehrmacht High Command. The high-level, strategic nature of the intelligence obtained from Tutte's crucial breakthrough, in the bulk decrypting of Lorenz-enciphered messages specifically, contributed greatly, and perhaps even decisively, to the defeat of Nazi Germany. He also had a number of significant mathematical accomplishments, including foundation work in the fields of graph theory and matroid theory.
Fish was the UK's GC&CS Bletchley Park codename for any of several German teleprinter stream ciphers used during World War II. Enciphered teleprinter traffic was used between German High Command and Army Group commanders in the field, so its intelligence value (Ultra) was of the highest strategic value to the Allies. This traffic normally passed over landlines, but as German forces extended their geographic reach beyond western Europe, they had to resort to wireless transmission.
The Lorenz SZ40, SZ42a and SZ42b were German rotor stream cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. The model name SZ was derived from Schlüssel-Zusatz, meaning cipher attachment. The instruments implemented a Vernam stream cipher.
The Siemens & Halske T52, also known as the Geheimschreiber, or Schlüsselfernschreibmaschine (SFM), was a World War II German cipher machine and teleprinter produced by the electrical engineering firm Siemens & Halske. The instrument and its traffic were codenamed Sturgeon by British cryptanalysts.
Brigadier John Hessell Tiltman, was a British Army officer who worked in intelligence, often at or with the Government Code and Cypher School (GC&CS) starting in the 1920s. His intelligence work was largely connected with cryptography, and he showed exceptional skill at cryptanalysis. His work in association with Bill Tutte on the cryptanalysis of the Lorenz cipher, the German teleprinter cipher, called "Tunny" at Bletchley Park, led to breakthroughs in attack methods on the code, without a computer. It was to exploit those methods, at extremely high speed with great reliability, that Colossus, the first digital programmable electronic computer, was designed and built.
Thomas Harold Flowers MBE was an English engineer with the British General Post Office. During World War II, Flowers designed and built Colossus, the world's first programmable electronic computer, to help decipher encrypted German messages.
Cryptography was used extensively during World War II because of the importance of radio communication and the ease of radio interception. The nations involved fielded a plethora of code and cipher systems, many of the latter using rotor machines. As a result, the theoretical and practical aspects of cryptanalysis, or codebreaking, were much advanced.
Captain Raymond C. "Jerry" Roberts MBE was a British wartime codebreaker and businessman. During the Second World War, Roberts worked at the Government Code and Cypher School (GC&CS) at Bletchley Park from 1941 to 1945. He was a leading codebreaker and linguist, who worked on the Lorenz cipher system – Hitler's most top-level code.
The Newmanry was a section at Bletchley Park, the British codebreaking station during World War II. Its job was to develop and employ statistical and machine methods in cryptanalysis of the Lorenz cipher. It worked very closely with the Testery where a complementary set of operations were performed to complete the decryption of each message. Formally called the Statistical section, it was known as the Newmanry after its founder and head, Max Newman. It was responsible for the various Robinson machines and the ten Colossus computers. Some of the cryptanalysts had joint appointments with the Testery.
Charles Eryl Wynn-Williams, was a Welsh physicist, noted for his research on electronic instrumentation for use in nuclear physics. His work on the scale-of-two counter contributed to the development of the modern computer.
The Testery was a section at Bletchley Park, the British codebreaking station during World War II. It was set up in July 1942 as the "FISH Subsection" under Major Ralph Tester, hence its alternative name. Four founder members were Tester himself and three senior cryptanalysts: Captain Jerry Roberts, Captain Peter Ericsson and Major Denis Oswald. All four were fluent in German. From 1 July 1942 on, this team switched and was tasked with breaking the German High Command's most top-level code Tunny after Bill Tutte successfully broke Tunny system in Spring 1942.
Ralph Paterson Tester was an administrator at Bletchley Park, the British codebreaking station during World War II. He founded and supervised a section named the Testery for breaking Tunny.
Turingery or Turing's method was a manual codebreaking method devised in July 1942 by the mathematician and cryptanalyst Alan Turing at the British Government Code and Cypher School at Bletchley Park during World War II. It was for use in cryptanalysis of the Lorenz cipher produced by the SZ40 and SZ42 teleprinter rotor stream cipher machines, one of the Germans' Geheimschreiber machines. The British codenamed non-Morse traffic "Fish", and that from this machine "Tunny".
Cryptanalysis of the Lorenz cipher was the process that enabled the British to read high-level German army messages during World War II. The British Government Code and Cypher School (GC&CS) at Bletchley Park decrypted many communications between the Oberkommando der Wehrmacht in Berlin and their army commands throughout occupied Europe, some of which were signed "Adolf Hitler, Führer". These were intercepted non-Morse radio transmissions that had been enciphered by the Lorenz SZ teleprinter rotor stream cipher attachments. Decrypts of this traffic became an important source of "Ultra" intelligence, which contributed significantly to Allied victory.
Dorothy Du Boisson, MBE was a code breaker stationed at Bletchley Park during World War II.
Harry William Fensom was an English electronic engineer with the GPO. During World War II he worked with Tommy Flowers at Bletchley Park on Colossus, the world's first electronic computer, that helped to decode encrypted German messages using the Lorenz cipher. After the war, he designed ERNIE, a machine based on Colossus engineering that was used to generate bond numbers for the Premium Bond draw.
Geoffrey Timms OBE FRSE (1903–1982) was a 20th century British mathematician and cryptoanalyst. In the Second World War he was one of the several mathematicians working alongside Alan Turing at Bletchley Park breaking the Enigma code.
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