![]() The Colossus was efficient for its purpose. Although valves were generally considered to be liable to high failure rates it was recognised that failure occurred at power on and off so the Colossus machines, once turned on, were never powered down until the end of the war. The machine is nearly complete, and has required over 6,000 man-days of volunteer work.Ĭolossus used state-of-the-art vacuum tubes ( 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". In 1994, a team led by Tony Sale began a reconstruction of a Colossus. Most were destroyed after the war as part of 'protecting secrets' although two survived for many years and were used during the cold war. Ten Mark II Colossus machines were in use at Bletchley Park by the end of the war. It was followed into service by the Mark II Colossus in June 1944. Work on the design of the Mark I started early in 1943, and the prototype was finished and installed by December 1943. ![]() Both models were programmable using switches and plug panels, in a way the Robinsons had not been. Initially Colossus was only used to determine the initial wheel positions used for a particular message (termed wheel setting) the Mark II included mechanisms intended to help determine pin patterns ( wheel breaking). The Colossus Mark II was simpler to operate as well as being more advanced, and so greatly speeded the deciphering process, which was largely still carried out by hand.Ĭolossus included the first ever use of shift registers and systolic arrays, 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). For comparison, ENIAC contained 1,800 vacuum tubes (electronic valves), and could perform 5,000 operations per second.Ĭolossus dispensed with the second tape by generating the wheel patterns electronically, and could process 5,000 characters (40 feet / 12m of tape) per second. ![]() Colossus contained 1,500 electronic valves and was programmable. He delivered the working machine to Bletchley on Decemtwo years prior to the completion of another early computer, ENIAC. Tommy Flowers, an engineer related to the codebreaking efforts at Bletchley, took the blueprints to the Post Office's research center at Dollis Hill, North London and spent ten months building Colossus. The main problem with the Robinsons was synchronising two paper tapes, one punched with the enciphered message, the other representing the patterns produced by the wheels of the Lorenz machine, that tended to stretch when being read at over 1000 characters per second. The idea for Colossus developed out of a prior project which produced a special purpose opto-mechanical comparator machine called the Heath Robinson, and its successors the Old Robinson and Super Robinson. ![]() Bill Tutte, a cryptanalyst at Bletchley Park, discovered that the keystream and ciphertext produced by the machine exhibited a very subtle statistical bias deviating from that would be expected from a random bitstream Colossus exploited these statistical weaknesses. The Lorenz machine generated a pseudo-random stream of bits, grouped in fives - a stream cipher. These machines were in the spirit of those first proposed by Colonel Parker Hitt of the US Army around WWI. The Colossus was designed for cryptanalysis to assist the reading of messages encrypted using the Lorenz SZ 40/42 machine, used for securing high-level German communications. Colossus was the first combining all of digital, (partially) programmable, and electronic. Babbage's Analytical engine antedated all these (in the mid-1800s), and was both digital and programmable, but was only partially constructed and never functioned at the time (a replica of his Difference engine No. Assorted analog computers were semiprogrammable, some of these much predated the 1930s (eg, Vannevar Bush). Zuse's Z3 computer was the world's 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). Colossus was designed by Tommy Flowers at the British Post Office Research Station, Dollis Hill.Ĭolossus was preceded by several computers, many first in some category. In World War II, Colossus machines were used to assist in breaking the German Lorenz SZ 40/42 machine, codenamed "Tunny" by the British. In the history of cryptography, the Colossus machines were the first programmable (to a limited extent) digital electronic computers. The slanted control panel on the left was used to set the pin patterns on the Lorenz the paper tape transport is on the right.
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