SafekipediaColossus computer
Adapted from Wikipedia · Discoverer experience
Colossus was a set of computers developed by British codebreakers between 1943 and 1945. These machines were created to help break the complex Lorenz cipher used by German leaders during World War II. Colossus used many small parts called thermionic valves (vacuum tubes) to perform logical and counting tasks, making it an important step in the history of computing.
The Colossus computers were designed by engineer Tommy Flowers, working with mathematician Max Newman at Bletchley Park, a secret center for codebreaking. Although famous scientist Alan Turing helped with codebreaking methods, he did not design Colossus; his work focused on a different machine called the Bombe used against another German code called Enigma.
The first Colossus machine, called Colossus Mark 1, began working in December 1943 and was used at Bletchley Park by early 1944. A faster version, the Colossus Mark 2, was ready by June 1944, just in time to help with the important Normandy landings on D-Day. By the end of the war, ten Colossus machines were in use, giving the Allies valuable information from intercepted German messages.
For many years, the existence of Colossus remained a secret. The machines were mostly dismantled, and details about them were not revealed until the 1970s. In 2008, a working reconstruction of a Colossus Mark 2 was completed and is now on display at The National Museum of Computing at Bletchley Park.
Purpose and origins
See also: Cryptanalysis of the Lorenz cipher
The Colossus computers were used to help decipher intercepted radio teleprinter messages that had been encrypted using an unknown device. The British called these encrypted messages "Fish" and the machine used to encrypt them "Tunny".
British experts figured out how the German machine worked and built their own version called "British Tunny". They discovered it used twelve wheels and a special method to mix messages. In 1941, a mistake by German operators helped British experts understand the machine's structure better.
To decrypt messages, two jobs needed to be done. The first was finding the patterns of the wheels, and the second was finding the starting positions of the wheels for each message. Colossus was designed to help with the second job by comparing message streams and counting certain patterns.
Decryption processes
The Colossus computer helped British codebreakers solve difficult secret messages during World War II. By looking at patterns in the messages, they could figure out important starting points for the machines used to create the codes. This made it much easier to read the messages.
Once they had these starting points, the team at Bletchley Park could use other methods to fully decode the messages. Later, Colossus could also help find the starting points for additional parts of the coding machine.
| P {\displaystyle P} | plaintext |
| K {\displaystyle K} | key – the sequence of characters used in binary XOR with the plaintext to give the ciphertext |
| χ {\displaystyle \chi } | chi component of key |
| ψ {\displaystyle \psi } | psi component of key |
| ψ ′ {\displaystyle \psi '} | extended psi – the actual sequence of characters added by the psi wheels, including those when they do not advance |
| Z {\displaystyle Z} | ciphertext |
| D {\displaystyle D} | de-chi—the ciphertext with the chi component of the key removed |
| Δ {\displaystyle \Delta } | any of the above XOR'ed with its successor character or bit |
| ⊕ {\displaystyle \oplus } | the XOR operation |
| ∙ {\displaystyle \bullet } | Bletchley Park shorthand for telegraphy code space (zero) |
| x {\displaystyle \mathbf {x} } | Bletchley Park shorthand for telegraphy code mark (one) |
Design and construction
Colossus was created for the "Newmanry", a group led by mathematician Max Newman that focused on breaking the Lorenz SZ40/42 on-line teleprinter cipher machine, called Tunny. The idea for Colossus came from a simpler machine called "Heath Robinson", which showed that machines could help with this work but had some problems, like slow speed and difficulty keeping tapes in sync.
Tommy Flowers MBE, an engineer, designed Colossus. He thought using electronic parts could solve the problems of the Heath Robinson machine. His first model, called Mark 1 Colossus, used 1,600 electronic parts called thermionic valves (or vacuum tubes) and worked well when tested. It was then moved to Bletchley Park, where it began decoding messages in February 1944. Later, an improved version called Mark 2 Colossus was made. This version was faster and easier to use, and it had 2,400 valves. The first Mark 2 was ready just in time to help with the Allied invasion of Normandy on D-Day. By the end of the war, ten Colossus machines were in use at Bletchley Park, helping to break coded messages.
Operation
The Newmanry was staffed by cryptanalysts, operators from the Women's Royal Naval Service (WRNS) – known as "Wrens" – and engineers for maintenance and repair. By the end of the war, there were 272 Wrens and 27 men working there.
To operate Colossus for a new message, the Wrens would prepare a paper tape loop by sticking the ends together with glue. They would also punch special holes to show where the message started and ended. The operator would then thread the tape through the machine and adjust it before starting the process under guidance from a cryptanalyst.
Programming
Colossus was not a stored-program computer. Instead, its operations were controlled using switches and connections on a panel. Each part of the machine could perform specific calculations and count how often certain results appeared.
Operators could choose different settings for the machine, allowing many different ways to analyze the encrypted messages. This flexibility helped break complex German codes during World War II.
Influence and fate
The Colossus computers were special machines made to help solve secret codes during World War II. Though they were the first electronic digital machines that could be programmed, they were not general-purpose computers and were mainly used for specific tasks.
After the war, most of the Colossus machines were taken apart, and their secret was kept for many years. Only a few parts were kept for research, and the full story of Colossus was not known until much later. Some people who worked on Colossus later helped develop new computers, but the machine itself did not directly shape modern computing because its existence was kept secret.
Reconstruction
A team led by Tony Sale built a fully functional version of the Colossus Mark 2 computer between 1993 and 2008. Even though many original plans were gone, they used old engineers’ notes and materials from the United States to rebuild it. The reconstruction can be seen at The National Museum of Computing in Bletchley Park, Milton Keynes, Buckinghamshire.
In November 2007, a special event called the Cipher Challenge tested the rebuilt Colossus. Radio amateurs around the world tried to decode secret messages sent from a museum in Germany. A radio amateur named Joachim Schüth won the challenge using a modern laptop, which decoded the messages much faster than the Colossus could. This event showed how well the reconstruction worked and honored the people who built the original Colossus during World War II.
Other meanings
See also: List of fictional computers
The name Colossus was used for a fictional computer in the 1970 film Colossus: The Forbin Project, based on a novel by D. F. Jones. This was a coincidence, as the film was made before the public learned about the real Colossus computer.
The name also appears in Neal Stephenson’s novel Cryptonomicon (1999), which talks about the history of Turing and Bletchley Park. There is also a Colossus (supercomputer), which is noted as the world's largest AI supercomputer.
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