Photos: A 'Cipher Challenge' for Colossus

Here's the vintage Colossus. Today's version took 14 years to assemble, according to Anthony Sale, who headed the team that rebuilt the computer.

"All the drawings were burnt in 1960, so all we had to go on were six black-and-white photos and 10 fragments of circuit diagrams," Sale said. "The machine has 2,500 valves, so it was a challenge piecing it all together."

Photo by Bletchley Park Trust