Colossus computer
Encyclopedia
Not to be confused with the fictional computer of the same name in the movie Colossus: The Forbin Project
.
Colossus was the world's first electronic
, digital
, programmable
computer
. Colossus and its successors were used by British codebreakers
to help read encrypted German
messages during World War II
. They used thermionic valves (vacuum tube
s) to perform the calculations.
Colossus was designed by engineer Tommy Flowers
with input from Sidney Broadhurst, William Chandler, Allen Coombs
and Harry Fensom. at the Post Office Research Station
, Dollis Hill
to solve a problem posed by mathematician Max Newman
at Bletchley Park
. The prototype, Colossus Mark 1, was shown to be working in December 1943 and was operational at Bletchley Park by February 1944. An improved Colossus Mark 2 first worked on 1 June 1944, just in time for the Normandy Landings. Ten Colossus computers were in use by the end of the war.
The Colossus computer
s were used to help decipher teleprinter
messages which had been encrypted
using the Lorenz SZ40/42 machine—British codebreakers referred to encrypted German teleprinter traffic as "Fish
" and called the SZ40/42 machine and its traffic "Tunny
". Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.
The Colossus was used to find possible key combinations for the Lorenz machines – rather than decrypting an intercepted message in its entirety.
In spite of the destruction of most of the Colossus hardware and blueprints as part of the effort to maintain a project secrecy that was kept up into the 1970s—a secrecy that deprived some of the Colossus creators of credit for their pioneering advancements in electronic digital computing during their lifetimes—a functional replica of a Colossus computer was completed in 2007.
The Colossus computers were used in the cryptanalysis
of high-level German communications, messages which had been encrypted using the Lorenz SZ 40/42 cipher machine; part of the operation of Colossus was to emulate the electromechanical Lorenz machine electronically. To encrypt a message with the Lorenz machine, the plaintext
was combined with a stream of key bit
s, grouped in fives. The keystream
was generated using twelve pinwheel
s: five were termed (by the British) χ ("chi
") wheels, another five ψ ("psi
") wheels, and the remaining two the "motor wheels". The χ wheels stepped regularly with each letter that was encrypted, while the ψ wheels stepped irregularly, controlled by the motor wheels.
Bill Tutte, a cryptanalyst at Bletchley Park
, discovered that the keystream produced by the machine exhibited statistical biases deviating from random, and that these biases could be used to break the cipher and read messages. In order to read messages, there were two tasks that needed to be performed. The first task was wheel breaking, which was discovering the pin patterns for all the wheels. These patterns were set up once on the Lorenz machine and then used for a fixed period of time and for a number of different messages. The second task was wheel setting, which could be attempted once the pin patterns were known. Each message encrypted using Lorenz was enciphered at a different start position for the wheels. The process of wheel setting found the start position for a message. Initially Colossus was used to help with wheel setting, but later it was found it could also be adapted to the process of wheel breaking as well.
Colossus was developed for the Newmanry
, the section at Bletchley Park responsible for machine methods against the Lorenz machine, headed by the mathematician Max Newman
. It arose out of a prior project which produced a special purpose opto-mechanical comparator and counting machine called "Heath Robinson
".
The main problems with the Heath Robinson were the relative slowness of electro-mechanical relays and the difficulty of synchronising two paper tapes
, one punched with the enciphered message, the other representing the patterns produced by the wheels of the Lorenz machine. The tapes tended to stretch when being read at some 2000 characters per second, resulting in unreliable counts. Tommy Flowers
of the Post Office Research Station
at Dollis Hill
was called in to look into the design of the Robinson’s combining unit. He was not impressed with the machines and, at his own initiative, designed an electronic machine which stored the data from one of the tapes internally. He presented this design to Max Newman in February 1943, but the idea that the one to two thousand thermionic valves (vacuum tubes) proposed, could work together reliably was greeted with scepticism, so more Robinsons were ordered from Dollis Hill. Flowers, however, persisted with the idea and obtained support from the Director of the Research Station.
spent eleven months (early February to December 1943) designing and building Colossus at the Post Office Research Station
, Dollis Hill
, in northwest London. After a functional test in December 1943, Colossus was dismantled and shipped north to Bletchley Park, where it was delivered on 18 January 1944 and assembled by Harry Fensom and Don Horwood, and attacked its first message on 5 February.
The Mark 1 was followed by nine Mark 2 Colossus machines, the first being commissioned in June 1944, and the original Mark 1 machine was converted into a Mark 2. An eleventh Colossus was essentially finished at the end of the war. Colossus Mark 1 contained 1,500 electronic valves (tubes). Colossus Mark 2 with 2,400 valves was both 5 times faster and simpler to operate than Mark 1, greatly speeding the decoding process. Mark 2 was designed while Mark 1 was being constructed. Allen Coombs
took over leadership of the Colossus Mark 2 project when Tommy Flowers
moved on to other projects. For comparison, later stored-program computers like the Manchester Mark 1
of 1949 used about 4,200 valves. In comparison, ENIAC
(1946) used 17,468 valves.
Colossus dispensed with the second tape of the Heath Robinson design by generating the wheel patterns electronically, and processing 5,000 characters per second with the paper tape moving at 40 ft/s (12.2 m/s or 27.3 mph). The circuits were synchronized by a clock signal
generated by the sprocket holes of the punched tape. The speed of calculation was thus limited by the mechanics of the tape reader. Tommy Flowers tested the tape reader up to 9,700 characters per second (53 mph) before the tape disintegrated. He settled on 5,000 characters/second as the desirable speed for regular operation. Sometimes, two or more Colossus computers tried different possibilities simultaneously in what now is called parallel computing
, speeding the decoding process by perhaps as much as doubling the rate of comparison.
Colossus included the first ever use of shift register
s and systolic array
s, enabling five simultaneous tests, each involving up to 100 Boolean calculations, on each of the five channels on the punched tape (although in normal operation only one or two channels were examined in any run).
Initially Colossus was only used to determine the initial wheel positions used for a particular message (termed wheel setting). The Mark 2 included mechanisms intended to help determine pin patterns (wheel breaking). Both models were programmable using switches and plug panels in a way the Robinsons had not been.
Colossus used state-of-the-art vacuum tube
s (thermionic valve
s), thyratron
s and photomultiplier
s to optically read a paper tape and then applied a programmable logical function to every character, counting how often this function returned "true". Although machines with many valves were known to have high failure rates, it was recognised that valve failures occurred most frequently with the current surge when powering up, so the Colossus machines, once turned on, were never powered down unless they malfunctioned.
Colossus was the first of the electronic digital machines with programmability, albeit limited by modern standards:
It was thus not a fully general Turing-complete computer, even though Alan Turing
worked at Bletchley Park
. 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—did not become prominent for several years.
Colossus was preceded by several computers, many of them first in some category. Zuse's
Z3 was the first functional fully program-controlled computer
, and was based on electromechanical relays, as were the (less advanced) Bell Labs
machines of the late 1930s (George Stibitz
, et al.). The Atanasoff–Berry Computer was electronic and binary (digital) but not programmable. Assorted analog computer
s were semiprogrammable; some of these much predated the 1930s (e.g., Vannevar Bush
). Babbage's Analytical engine
design predated all these (in the mid-19th century), it was a decimal, programmable, entirely mechanical construction—but was only partially built and never functioned during Babbage's lifetime (the first complete mechanical Difference engine No. 2
, built in 1991, does work however). Colossus was the first combining digital, (partially) programmable, and electronic. The first fully programmable digital electronic computer was the ENIAC
which was completed in 1946.
for many years, and Flowers and his associates also were deprived of the recognition they were due.
Being not widely known, it therefore had little direct influence on the development of later computers; EDVAC
was the early design which had the most influence on subsequent computer architecture.
However, the technology of Colossus, and the knowledge that reliable high-speed electronic digital computing devices were feasible, had a significant influence on the development of early computers in Britain and probably in the US. A number of people who were associated with the project and knew all about Colossus played significant roles in early computer work in Britain. In 1972, Herman Goldstine wrote that:
In writing that, Goldstine was unaware of Colossus, and its legacy to those projects of people such as Alan Turing
(with the Pilot ACE
and ACE
), and Max Newman and I. J. Good
(with the Manchester Mark 1
and other early Manchester computers). Brian Randell
later wrote that:
Colossus documentation and hardware were classified
from the moment of their creation and remained so after the War, when Winston Churchill
specifically ordered the destruction of most of the Colossus machines into "pieces no bigger than a man's hand"; Tommy Flowers personally burned blueprints in a furnace at Dollis Hill. Some parts, sanitised as to their original use, were taken to Newman's Royal Society
Computing Machine Laboratory
at Manchester University. The Colossus Mark 1 was dismantled and parts returned to the Post Office. Two Colossus computers, along with two replica Tunny machines, were retained, moving to GCHQ's new headquarters at Eastcote
in April 1946, and moving again with GCHQ to Cheltenham
between 1952 and 1954. One of the Colossi, known as Colossus Blue, was dismantled in 1959; the other in 1960. In their later years, the Colossi were used for training, but before that, there had been attempts to adapt them, with varying success, to other purposes. Jack Good relates how he was the first to use it after the war, persuading NSA that Colossus could be used to perform a function for which they were planning to build a special purpose machine. Colossus was also used to perform character counts on one-time pad
tape to test for non-randomness.
Throughout this period the Colossus remained secret, long after any of its technical details were of any importance. This was due to the UK's intelligence agencies use of Enigma-like machines which they promoted and sold to other governments, and then broke the codes using a variety of methods. Had the knowledge of the codebreaking machines been widely known, no one would have accepted these machines; rather, they would have developed their own methods for encryption, methods that the UK services might not have been able to break. The need for such secrecy ebbed away as communications moved to digital transmission and all-digital encryption systems became common in the 1960s.
Information about Colossus began to emerge publicly in the late 1970s, after the secrecy imposed was broken when Colonel Winterbotham published his book The Ultra Secret. More recently, a 500-page technical report on the Tunny cipher and its cryptanalysis – entitled General Report on Tunny – was released by GCHQ to the national Public Record Office
in October 2000; the complete report is available online, and it contains a fascinating paean
to Colossus by the cryptographers who worked with it:
Construction of a fully functional replica of a Colossus Mark 2 was undertaken by a team led by Tony Sale. In spite of the blueprints and hardware being destroyed, a surprising amount of material survived, mainly in engineers' notebooks, but a considerable amount of it in the U.S. The optical tape reader might have posed the biggest problem, but Dr. Arnold Lynch, its original designer, was able to redesign it to his own original specification. The reconstruction is on display, in the historically correct place for Colossus No. 9, at The National Museum of Computing
, in H Block Bletchley Park
in Milton Keynes
, Buckinghamshire
.
In November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for The National Museum of Computing
, a Cipher Challenge pitted the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode three 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 Ada
. The Colossus team were 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 codebreaker 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."
The Cipher Challenge verified the successful completion of the rebuild project. "On the strength of today's performance Colossus is as good as it was six decades ago", commented Tony Sale. "We are delighted to have produced a fitting tribute to the people who worked at Bletchley Park and whose brainpower devised these fantastic machines which broke these ciphers and shortened the war by many months."
. Also see List of fictional computers. Neal Stephenson
's novel Cryptonomicon
(1999) also contains a fictional treatment of the historical role played by Turing and Bletchley Park.
Colossus: The Forbin Project
Colossus: The Forbin Project is an American science fiction thriller film. It is based upon the 1966 novel Colossus, by Dennis Feltham Jones, about a massive American defense computer, named Colossus, becoming sentient and deciding to assume control of the world.-Plot:Dr. Charles A...
.
Colossus was the world's first electronic
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
, digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
, programmable
Computer programming
Computer programming is the process of designing, writing, testing, debugging, and maintaining the source code of computer programs. This source code is written in one or more programming languages. The purpose of programming is to create a program that performs specific operations or exhibits a...
computer
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
. Colossus and its successors were used by British codebreakers
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
to help read encrypted German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
messages during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. They used thermionic valves (vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s) to perform the calculations.
Colossus was designed by engineer Tommy Flowers
Tommy Flowers
Thomas "Tommy" Harold Flowers, MBE was an English engineer. During World War II, Flowers designed Colossus, the world's first programmable electronic computer, to help solve encrypted German messages.-Early life:...
with input from Sidney Broadhurst, William Chandler, Allen Coombs
Allen Coombs
Allen William Mark Coombs was a British electronics engineer at the Post Office Research Station, Dollis Hill...
and Harry Fensom. at the Post Office Research Station
Post Office Research Station
The Post Office Research Station at Dollis Hill, London, was first established in 1921 and opened by Prime Minister Ramsay MacDonald in 1933.In 1943 the world's first programmable electronic computer, Colossus Mark 1 was built by Tommy Flowers and his team, followed in 1944 and 1945 by nine...
, Dollis Hill
Dollis Hill
Dollis Hill is an area of north-west London. It lies close to Willesden, in the London Borough of Brent. As a result, Dollis Hill is sometimes referred as being part of Willesden, especially by the national press...
to solve a problem posed by mathematician Max Newman
Max Newman
Maxwell Herman Alexander "Max" Newman, FRS was a British mathematician and codebreaker.-Pre–World War II:Max Newman was born Maxwell Neumann in Chelsea, London, England, on 7 February 1897...
at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
. The prototype, Colossus Mark 1, was shown to be working in December 1943 and was operational at Bletchley Park by February 1944. An improved Colossus Mark 2 first worked on 1 June 1944, just in time for the Normandy Landings. Ten Colossus computers were in use by the end of the war.
The Colossus computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s were used to help decipher teleprinter
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
messages which had been encrypted
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
using the Lorenz SZ40/42 machine—British codebreakers referred to encrypted German teleprinter traffic as "Fish
Fish (cryptography)
Fish was the Allied 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 was of the highest strategic value to the Allies...
" and called the SZ40/42 machine and its traffic "Tunny
Lorenz cipher
The Lorenz SZ40, SZ42A and SZ42B were German rotor cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. They implemented a Vernam stream cipher...
". Colossus compared two data streams, counting each match based on a programmable Boolean function. The encrypted message was read at high speed from a paper tape. The other stream was generated internally, and was an electronic simulation of the Lorenz machine at various trial settings. If the match count for a setting was above a certain threshold, it would be sent as output to an electric typewriter.
The Colossus was used to find possible key combinations for the Lorenz machines – rather than decrypting an intercepted message in its entirety.
In spite of the destruction of most of the Colossus hardware and blueprints as part of the effort to maintain a project secrecy that was kept up into the 1970s—a secrecy that deprived some of the Colossus creators of credit for their pioneering advancements in electronic digital computing during their lifetimes—a functional replica of a Colossus computer was completed in 2007.
Purpose and origins
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
of high-level German communications, messages which had been encrypted using the Lorenz SZ 40/42 cipher machine; part of the operation of Colossus was to emulate the electromechanical Lorenz machine electronically. To encrypt a message with the Lorenz machine, the plaintext
Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Before the computer era, plaintext most commonly meant message text in the language of the communicating parties....
was combined with a stream of key bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s, grouped in fives. The keystream
Keystream
In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message ....
was generated using twelve pinwheel
Pinwheel (cryptography)
In cryptography, a pinwheel was a device for producing a short pseudorandom sequence of bits , as a component in a cipher machine. A pinwheel consisted of a rotating wheel with a certain number of positions on its periphery. Each position had a "pin" or "lug" which could be either "set" or "unset"...
s: five were termed (by the British) χ ("chi
Chi (letter)
Chi is the 22nd letter of the Greek alphabet, pronounced as in English.-Greek:-Ancient Greek:Its value in Ancient Greek was an aspirated velar stop .-Koine Greek:...
") wheels, another five ψ ("psi
Psi (letter)
Psi is the 23rd letter of the Greek alphabet and has a numeric value of 700. In both Classical and Modern Greek, the letter indicates the combination /ps/ . The letter was adopted into the Old Italic alphabet, and its shape is continued into the Algiz rune of the Elder Futhark...
") wheels, and the remaining two the "motor wheels". The χ wheels stepped regularly with each letter that was encrypted, while the ψ wheels stepped irregularly, controlled by the motor wheels.
Bill Tutte, a cryptanalyst at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
, discovered that the keystream produced by the machine exhibited statistical biases deviating from random, and that these biases could be used to break the cipher and read messages. In order to read messages, there were two tasks that needed to be performed. The first task was wheel breaking, which was discovering the pin patterns for all the wheels. These patterns were set up once on the Lorenz machine and then used for a fixed period of time and for a number of different messages. The second task was wheel setting, which could be attempted once the pin patterns were known. Each message encrypted using Lorenz was enciphered at a different start position for the wheels. The process of wheel setting found the start position for a message. Initially Colossus was used to help with wheel setting, but later it was found it could also be adapted to the process of wheel breaking as well.
Colossus was developed for the Newmanry
Newmanry
The Newmanry was a section at Bletchley Park, the British codebreaking station during World War II. Its job was to develop and employ machine methods in Cryptanalysis of the Lorenz cipher. The Newmanry was named after its founder and head, Max Newman...
, the section at Bletchley Park responsible for machine methods against the Lorenz machine, headed by the mathematician Max Newman
Max Newman
Maxwell Herman Alexander "Max" Newman, FRS was a British mathematician and codebreaker.-Pre–World War II:Max Newman was born Maxwell Neumann in Chelsea, London, England, on 7 February 1897...
. It arose out of a prior project which produced a special purpose opto-mechanical comparator and counting machine called "Heath Robinson
Heath Robinson (codebreaking machine)
Heath Robinson was a machine used by British codebreakers at Bletchley Park during World War II to solve messages in the German teleprinter cipher used by the Lorenz SZ40/42 cipher machine; the cipher and machine were called "Tunny" by the codebreakers, who named different German teleprinter...
".
The main problems with the Heath Robinson were the relative slowness of electro-mechanical relays and the difficulty of synchronising two paper tapes
Punched tape
Punched tape or paper tape is an obsolete form of data storage, consisting of a long strip of paper in which holes are punched to store data...
, one punched with the enciphered message, the other representing the patterns produced by the wheels of the Lorenz machine. The tapes tended to stretch when being read at some 2000 characters per second, resulting in unreliable counts. Tommy Flowers
Tommy Flowers
Thomas "Tommy" Harold Flowers, MBE was an English engineer. During World War II, Flowers designed Colossus, the world's first programmable electronic computer, to help solve encrypted German messages.-Early life:...
of the Post Office Research Station
Post Office Research Station
The Post Office Research Station at Dollis Hill, London, was first established in 1921 and opened by Prime Minister Ramsay MacDonald in 1933.In 1943 the world's first programmable electronic computer, Colossus Mark 1 was built by Tommy Flowers and his team, followed in 1944 and 1945 by nine...
at Dollis Hill
Dollis Hill
Dollis Hill is an area of north-west London. It lies close to Willesden, in the London Borough of Brent. As a result, Dollis Hill is sometimes referred as being part of Willesden, especially by the national press...
was called in to look into the design of the Robinson’s combining unit. He was not impressed with the machines and, at his own initiative, designed an electronic machine which stored the data from one of the tapes internally. He presented this design to Max Newman in February 1943, but the idea that the one to two thousand thermionic valves (vacuum tubes) proposed, could work together reliably was greeted with scepticism, so more Robinsons were ordered from Dollis Hill. Flowers, however, persisted with the idea and obtained support from the Director of the Research Station.
The construction of Colossus
Tommy FlowersTommy Flowers
Thomas "Tommy" Harold Flowers, MBE was an English engineer. During World War II, Flowers designed Colossus, the world's first programmable electronic computer, to help solve encrypted German messages.-Early life:...
spent eleven months (early February to December 1943) designing and building Colossus at the Post Office Research Station
Post Office Research Station
The Post Office Research Station at Dollis Hill, London, was first established in 1921 and opened by Prime Minister Ramsay MacDonald in 1933.In 1943 the world's first programmable electronic computer, Colossus Mark 1 was built by Tommy Flowers and his team, followed in 1944 and 1945 by nine...
, Dollis Hill
Dollis Hill
Dollis Hill is an area of north-west London. It lies close to Willesden, in the London Borough of Brent. As a result, Dollis Hill is sometimes referred as being part of Willesden, especially by the national press...
, in northwest London. After a functional test in December 1943, Colossus was dismantled and shipped north to Bletchley Park, where it was delivered on 18 January 1944 and assembled by Harry Fensom and Don Horwood, and attacked its first message on 5 February.
The Mark 1 was followed by nine Mark 2 Colossus machines, the first being commissioned in June 1944, and the original Mark 1 machine was converted into a Mark 2. An eleventh Colossus was essentially finished at the end of the war. Colossus Mark 1 contained 1,500 electronic valves (tubes). Colossus Mark 2 with 2,400 valves was both 5 times faster and simpler to operate than Mark 1, greatly speeding the decoding process. Mark 2 was designed while Mark 1 was being constructed. Allen Coombs
Allen Coombs
Allen William Mark Coombs was a British electronics engineer at the Post Office Research Station, Dollis Hill...
took over leadership of the Colossus Mark 2 project when Tommy Flowers
Tommy Flowers
Thomas "Tommy" Harold Flowers, MBE was an English engineer. During World War II, Flowers designed Colossus, the world's first programmable electronic computer, to help solve encrypted German messages.-Early life:...
moved on to other projects. For comparison, later stored-program computers like the Manchester Mark 1
Manchester Mark 1
The Manchester Mark 1 was one of the earliest stored-program computers, developed at the Victoria University of Manchester from the Small-Scale Experimental Machine or "Baby" . It was also called the Manchester Automatic Digital Machine, or MADM...
of 1949 used about 4,200 valves. In comparison, ENIAC
ENIAC
ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....
(1946) used 17,468 valves.
Colossus dispensed with the second tape of the Heath Robinson design by generating the wheel patterns electronically, and processing 5,000 characters per second with the paper tape moving at 40 ft/s (12.2 m/s or 27.3 mph). The circuits were synchronized by a clock signal
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...
generated by the sprocket holes of the punched tape. The speed of calculation was thus limited by the mechanics of the tape reader. Tommy Flowers tested the tape reader up to 9,700 characters per second (53 mph) before the tape disintegrated. He settled on 5,000 characters/second as the desirable speed for regular operation. Sometimes, two or more Colossus computers tried different possibilities simultaneously in what now is called parallel computing
Parallel computing
Parallel computing is a form of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently . There are several different forms of parallel computing: bit-level,...
, speeding the decoding process by perhaps as much as doubling the rate of comparison.
Colossus included the first ever use of shift register
Shift register
In digital circuits, a shift register is a cascade of flip flops, sharing the same clock, which has the output of any one but the last flip-flop connected to the "data" input of the next one in the chain, resulting in a circuit that shifts by one position the one-dimensional "bit array" stored in...
s and systolic array
Systolic array
In computer architecture, a systolic array is a pipe network arrangement of processing units called cells. It is a specialized form of parallel computing, where cells , compute data and store it independently of each other.thumb|240px...
s, enabling five simultaneous tests, each involving up to 100 Boolean calculations, on each of the five channels on the punched tape (although in normal operation only one or two channels were examined in any run).
Initially Colossus was only used to determine the initial wheel positions used for a particular message (termed wheel setting). The Mark 2 included mechanisms intended to help determine pin patterns (wheel breaking). Both models were programmable using switches and plug panels in a way the Robinsons had not been.
Design and operation
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s (thermionic valve
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s), thyratron
Thyratron
A thyratron is a type of gas filled tube used as a high energy electrical switch and controlled rectifier. Triode, tetrode and pentode variations of the thyratron have been manufactured in the past, though most are of the triode design...
s and photomultiplier
Photomultiplier
Photomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...
s to optically read a paper tape and then applied a programmable logical function to every character, counting how often this function returned "true". Although machines with many valves were known to have high failure rates, it was recognised that valve failures occurred most frequently with the current surge when powering up, so the Colossus machines, once turned on, were never powered down unless they malfunctioned.
Colossus was the first of the electronic digital machines with programmability, albeit limited by modern standards:
- it had no internally stored programs. To set it up for a new task, the operator had to set up plugs and switches to alter the wiring.
- Colossus was not a general-purpose machine, being designed for a specific cryptanalytic task involving counting and Boolean operations.
It was thus not a fully general Turing-complete computer, even though Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
worked at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
. 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
Harvard Mark I
The IBM Automatic Sequence Controlled Calculator , called the Mark I by Harvard University, was an electro-mechanical computer....
electro-mechanical relay machine, the Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
relay machines (by George Stibitz
George Stibitz
George Robert Stibitz is internationally recognized as one of the fathers of the modern digital computer...
et al.), or the first designs of Konrad Zuse
Konrad Zuse
Konrad Zuse was a German civil engineer and computer pioneer. His greatest achievement was the world's first functional program-controlled Turing-complete computer, the Z3, which became operational in May 1941....
). The notion of a computer as a general purpose machine—that is, as more than a calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
devoted to solving difficult but specific problems—did not become prominent for several years.
Colossus was preceded by several computers, many of them first in some category. Zuse's
Konrad Zuse
Konrad Zuse was a German civil engineer and computer pioneer. His greatest achievement was the world's first functional program-controlled Turing-complete computer, the Z3, which became operational in May 1941....
Z3 was the first functional fully program-controlled computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
, and was based on electromechanical relays, as were the (less advanced) Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
machines of the late 1930s (George Stibitz
George Stibitz
George Robert Stibitz is internationally recognized as one of the fathers of the modern digital computer...
, et al.). The Atanasoff–Berry Computer was electronic and binary (digital) but not programmable. Assorted analog computer
Analog computer
An analog computer is a form of computer that uses the continuously-changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved...
s were semiprogrammable; some of these much predated the 1930s (e.g., Vannevar Bush
Vannevar Bush
Vannevar Bush was an American engineer and science administrator known for his work on analog computing, his political role in the development of the atomic bomb as a primary organizer of the Manhattan Project, the founding of Raytheon, and the idea of the memex, an adjustable microfilm viewer...
). Babbage's Analytical engine
Analytical engine
The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician Charles Babbage. It was first described in 1837 as the successor to Babbage's difference engine, a design for a mechanical calculator...
design predated all these (in the mid-19th century), it was a decimal, programmable, entirely mechanical construction—but was only partially built and never functioned during Babbage's lifetime (the first complete mechanical Difference engine No. 2
Difference engine
A difference engine is an automatic, mechanical calculator designed to tabulate polynomial functions. Both logarithmic and trigonometric functions can be approximated by polynomials, so a difference engine can compute many useful sets of numbers.-History:...
, built in 1991, does work however). Colossus was the first combining digital, (partially) programmable, and electronic. The first fully programmable digital electronic computer was the ENIAC
ENIAC
ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....
which was completed in 1946.
Influence and fate
The use to which the Colossus computers were put was of the highest secrecy, and the Colossus itself was highly secret, and remained so for many years after the War. Thus, Colossus could not be included in the history of computing hardwareHistory of computing hardware
The history of computing hardware is the record of the ongoing effort to make computer hardware faster, cheaper, and capable of storing more data....
for many years, and Flowers and his associates also were deprived of the recognition they were due.
Being not widely known, it therefore had little direct influence on the development of later computers; EDVAC
EDVAC
EDVAC was one of the earliest electronic computers. Unlike its predecessor the ENIAC, it was binary rather than decimal, and was a stored program computer....
was the early design which had the most influence on subsequent computer architecture.
However, the technology of Colossus, and the knowledge that reliable high-speed electronic digital computing devices were feasible, had a significant influence on the development of early computers in Britain and probably in the US. A number of people who were associated with the project and knew all about Colossus played significant roles in early computer work in Britain. In 1972, Herman Goldstine wrote that:
In writing that, Goldstine was unaware of Colossus, and its legacy to those projects of people such as Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
(with the Pilot ACE
Pilot ACE
The Pilot ACE was one of the first computers built in the United Kingdom, at the National Physical Laboratory in the early 1950s.It was a preliminary version of the full ACE, which had been designed by Alan Turing. After Turing left NPL , James H...
and ACE
ACE (computer)
The Automatic Computing Engine was an early electronic stored-program computer design produced by Alan Turing at the invitation of John R. Womersley, superintendent of the Mathematics Division of the National Physical Laboratory . The use of the word Engine was in homage to Charles Babbage and his...
), and Max Newman and I. J. Good
I. J. Good
Irving John Good was a British mathematician who worked as a cryptologist at Bletchley Park with Alan Turing. After World War II, Good continued to work with Turing on the design of computers and Bayesian statistics at the University of Manchester...
(with the Manchester Mark 1
Manchester Mark 1
The Manchester Mark 1 was one of the earliest stored-program computers, developed at the Victoria University of Manchester from the Small-Scale Experimental Machine or "Baby" . It was also called the Manchester Automatic Digital Machine, or MADM...
and other early Manchester computers). Brian Randell
Brian Randell
Brian Randell is a British computer scientist, and Emeritus Professor at the School of Computing Science, Newcastle University, U.K. He specializes in research in software fault tolerance and dependability, and is a noted authority on the early prior to 1950 history of computers.- Biography...
later wrote that:
Colossus documentation and hardware were classified
Classified information
Classified information is sensitive information to which access is restricted by law or regulation to particular groups of persons. A formal security clearance is required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation...
from the moment of their creation and remained so after the War, when Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
specifically ordered the destruction of most of the Colossus machines into "pieces no bigger than a man's hand"; Tommy Flowers personally burned blueprints in a furnace at Dollis Hill. Some parts, sanitised as to their original use, were taken to Newman's Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
Computing Machine Laboratory
Computing Machine Laboratory
Max Newman established the Royal Society Computing Machine Laboratory at Manchester University, shortly after the end of World War II, around 1946. The Laboratory was funded through a grant from the Royal Society which was approved in the summer of 1946...
at Manchester University. The Colossus Mark 1 was dismantled and parts returned to the Post Office. Two Colossus computers, along with two replica Tunny machines, were retained, moving to GCHQ's new headquarters at Eastcote
Eastcote
Eastcote is a suburban area established around an old village in Greater London, and is part of the London Borough of Hillingdon.In the Middle Ages, Eastcote was one of the three areas that made up the parish of Ruislip, under the name of Ascot...
in April 1946, and moving again with GCHQ to Cheltenham
Cheltenham
Cheltenham , also known as Cheltenham Spa, is a large spa town and borough in Gloucestershire, on the edge of the Cotswolds in the South-West region of England. It is the home of the flagship race of British steeplechase horse racing, the Gold Cup, the main event of the Cheltenham Festival held...
between 1952 and 1954. One of the Colossi, known as Colossus Blue, was dismantled in 1959; the other in 1960. In their later years, the Colossi were used for training, but before that, there had been attempts to adapt them, with varying success, to other purposes. Jack Good relates how he was the first to use it after the war, persuading NSA that Colossus could be used to perform a function for which they were planning to build a special purpose machine. Colossus was also used to perform character counts on one-time pad
One-time pad
In cryptography, the one-time pad is a type of encryption, which has been proven to be impossible to crack if used correctly. Each bit or character from the plaintext is encrypted by a modular addition with a bit or character from a secret random key of the same length as the plaintext, resulting...
tape to test for non-randomness.
Throughout this period the Colossus remained secret, long after any of its technical details were of any importance. This was due to the UK's intelligence agencies use of Enigma-like machines which they promoted and sold to other governments, and then broke the codes using a variety of methods. Had the knowledge of the codebreaking machines been widely known, no one would have accepted these machines; rather, they would have developed their own methods for encryption, methods that the UK services might not have been able to break. The need for such secrecy ebbed away as communications moved to digital transmission and all-digital encryption systems became common in the 1960s.
Information about Colossus began to emerge publicly in the late 1970s, after the secrecy imposed was broken when Colonel Winterbotham published his book The Ultra Secret. More recently, a 500-page technical report on the Tunny cipher and its cryptanalysis – entitled General Report on Tunny – was released by GCHQ to the national Public Record Office
Public Record Office
The Public Record Office of the United Kingdom is one of the three organisations that make up the National Archives...
in October 2000; the complete report is available online, and it contains a fascinating paean
Paean
A paean is a song or lyric poem expressing triumph or thanksgiving. In classical antiquity, it is usually performed by a chorus, but some examples seem intended for an individual voice...
to Colossus by the cryptographers who worked with it:
Reconstruction
The National Museum of Computing
The National Museum of Computing is a museum in the United Kingdom dedicated to collecting and restoring historic computer systems. The museum is based at Bletchley Park in Buckinghamshire, England, and opened in 2007...
, in H Block Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
in Milton Keynes
Milton Keynes
Milton Keynes , sometimes abbreviated MK, is a large town in Buckinghamshire, in the south east of England, about north-west of London. It is the administrative centre of the Borough of Milton Keynes...
, Buckinghamshire
Buckinghamshire
Buckinghamshire is a ceremonial and non-metropolitan home county in South East England. The county town is Aylesbury, the largest town in the ceremonial county is Milton Keynes and largest town in the non-metropolitan county is High Wycombe....
.
In November 2007, to celebrate the project completion and to mark the start of a fundraising initiative for The National Museum of Computing
The National Museum of Computing
The National Museum of Computing is a museum in the United Kingdom dedicated to collecting and restoring historic computer systems. The museum is based at Bletchley Park in Buckinghamshire, England, and opened in 2007...
, a Cipher Challenge pitted the rebuilt Colossus against radio amateurs worldwide in being first to receive and decode three 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 Ada
Ada (programming language)
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
. The Colossus team were hampered by their wish to use World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
radio equipment, delaying them by a day because of poor reception conditions. Nevertheless the victor's 1.4 GHz laptop
Laptop
A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
, running his own code, took less than a minute to find the settings for all 12 wheels. The German codebreaker 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."
The Cipher Challenge verified the successful completion of the rebuild project. "On the strength of today's performance Colossus is as good as it was six decades ago", commented Tony Sale. "We are delighted to have produced a fitting tribute to the people who worked at Bletchley Park and whose brainpower devised these fantastic machines which broke these ciphers and shortened the war by many months."
See also
- History of computing hardwareHistory of computing hardwareThe history of computing hardware is the record of the ongoing effort to make computer hardware faster, cheaper, and capable of storing more data....
- Z3
- SupercomputerSupercomputerA supercomputer is a computer at the frontline of current processing capacity, particularly speed of calculation.Supercomputers are used for highly calculation-intensive tasks such as problems including quantum physics, weather forecasting, climate research, molecular modeling A supercomputer is a...
- Enigma MachineEnigma machineAn Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
- Lorenz CipherLorenz cipherThe Lorenz SZ40, SZ42A and SZ42B were German rotor cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. They implemented a Vernam stream cipher...
Further reading
- Harvey G. Cragon, From Fish to Colossus: How the German Lorenz Cipher was Broken at Bletchley Park (Cragon Books, Dallas, 2003; ISBN 0-9743045-0-6) – A detailed description of the cryptanalysis of Tunny, and some details of Colossus (contains some minor errors)
- Ted Enever, Britain's Best Kept Secret: Ultra's Base at Bletchley Park (Sutton Publishing, Gloucestershire, 1999; ISBN 0-7509-2355-5) – A guided tour of the history and geography of the Park, written by one of the founder members of the Bletchley Park Trust
- Tony Sale, The Colossus Computer 1943–1996: How It Helped to Break the German Lorenz Cipher in WWII (M.&M. Baldwin, Kidderminster, 2004; ISBN 0-947712-36-4) – A slender (20 page) booklet, containing the same material as Tony Sale's website (see below)
- Michael Smith, Station X, 1998. ISBN 0-330-41929-3.
- Jack Copeland: Colossus. The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press 2006. ISBN 0-19-284055-X
- R. Rojas, U. Hashagen (eds.): The First Computers: History and Architectures. MIT Press 2000. ISBN 0-262-18197-5. – Comparison of the first computers, with a chapter about Colossus and its reconstruction by Tony Sale.
Other meanings
There was a fictional computer named Colossus in the movie Colossus: The Forbin ProjectColossus: The Forbin Project
Colossus: The Forbin Project is an American science fiction thriller film. It is based upon the 1966 novel Colossus, by Dennis Feltham Jones, about a massive American defense computer, named Colossus, becoming sentient and deciding to assume control of the world.-Plot:Dr. Charles A...
. Also see List of fictional computers. Neal Stephenson
Neal Stephenson
Neal Town Stephenson is an American writer known for his works of speculative fiction.Difficult to categorize, his novels have been variously referred to as science fiction, historical fiction, cyberpunk, and postcyberpunk...
's novel Cryptonomicon
Cryptonomicon
Cryptonomicon is a 1999 novel by American author Neal Stephenson. The novel follows the exploits of two groups of people in two different time periods, presented in alternating chapters...
(1999) also contains a fictional treatment of the historical role played by Turing and Bletchley Park.
External links
- The National Museum of Computing
- Tony Sale's Codes and Ciphers Contains a great deal of information, including:
- Colossus, the revolution in code breaking
- Lorenz Cipher and the Colossus
- The machine age comes to Fish codebreaking
- The Colossus Rebuild Project
- The Colossus Rebuild Project: Evolving to the Colossus Mk 2
- Walk around Colossus A detailed tour of the replica Colossus – make sure to click on the "More Text" links on each image to see the informative detailed text about that part of Colossus
- IEEE lecture – Transcript of a lecture Tony Sale gave describing the reconstruction project
- BBC news article reporting on the replica Colossus
- BBC news article: "Colossus cracks codes once more"
- BBC news article: BBC news article: "Bletchley's code-cracking Colossus" with video interviews 2010-02-02
- Website on Copeland's 2006 book with much information and links to recently declassified information
- Was the Manchester Baby conceived at Bletchley Park?