German amateur cracks WWII mega-code in 46 seconds

The Lorenz cipher is based on wheels that can have an almost infinite range of settings.

Colossus, a truck-sized computer built in 1943-4 with the help of mathematicians such as Enigma code breaker Alan Turing, has worked out five of the wheel settings so far and is expected to complete the task in about six hours.

Clark was full of praise for Schueth, who German scientists who helped design the challenge said they had never heard of. He hopes Schueth will visit Bletchley Park to receive a reward.

Colossus was a top-secret project during World War Two -- it only came to light in the 1970s -- that helped crack secret German commands on troop movements and supplies. Winston Churchill, Britain's war-time prime minister, credited it with helping to shorten the war by up to 18 months.