The world’s first electronic computer created by the British to decrypt Adolf Hitler’s secret messages during World War II turned 70 on February 5. Some of Britain’s best known code breakers who operated the ‘Colossus’ gathered at UK’s National Museum of Computing to celebrate seven decades of it’s existence. Designed by British telephone engineer Tommy Flowers, Colossus was built to speed up code-breaking of the complex Lorenz cipher used in communications between Hitler and his generals during World War II. It is widely thought to have shortened the war and saved countless lives. On February 5, 1944 Colossus Mk I worked on its first Lorenzencrypted message.

By the end of the war, 63 million characters of high-grade German messages had been decrypted by the 550 people working on the 10 functioning colossi during the war. Colossus occupied the size of a living room (7 feet high by 17 feet wide and 11 feet deep), weighed five tons, incorporated 2,500 valves and 10,000 resistors connected by 7 km of wiring. Its existence was kept top secret for 30 years because of the sensitivity surrounding the encryption messages it had helped to break. German teleprinter signals encrypted by Lorenz machines were first found by police looking for possible spy transmissions in 1940 in the UK.

In August 1941, a procedural error by a German operator enabled Colonel John Tiltman – a top code-breaker decipher a German message. Mathematician Bill Tutte then began working on the case and was able to deduce the complete logical structure of the cipher machine. Code-breakers then began breaking the codes by hand but this was very time consuming. Flowers who was then a post office electronics engineer designed Colossus which helped break codes in a few hours thereby greatly shortening the process and enabling larger numbers of messages to be broken. Tim Reynolds, chair of Britain’s National Museum of Computing said, “The achievements of those who worked at Bletchley Park are humbling.

Tutte’s ingenuity in deducing out how the Lorenz machine worked without ever having seen it, the skill of those who broke the cipher by hand and Flowers’ design of the world’s first electronic computer Colossus to speed up the code-breaking process are feats almost beyond comprehension.” In honor of the men and women who worked at Bletchley Park during World War II, Tony Sale, co-founder of The National Museum of Computing led a team to rebuild Colossus in 1994. They worked with eight photographs of Colossus taken in 1945. A few circuit diagrams kept by engineers who worked on the original computer were also obtained. On Nov 15, 2007, a rebuilt fully-functioning Colossus Mark II was unveiled to the public.