I was able to find the program online, but it requires a bit of fiddling to download & play it. It is 1.5 GBytes & 60 minutes in length, but well worth watching. It describes Colossus, which used paper tape as its input. From the brief description in the TV program, the German code appeared to be a "one-time" XOR pad, except that the "random" bits were generated by a pseudo-random bit generator that wasn't random enough. It would be interesting to see if the methods in Knuth on testing pseudo-random bit generators would work on this German code. Because storage in the form of vacuum tubes ("valves") was so expensive, the paper tape input was tied end-to-end and cycled endlessly for each scan of the input data. Because of these long loops of paper tape, Colossus looked a lot like a late 19th century factory where a system of belts conveyed power before the invention of small electric motors. I guess these recirculating paper tapes became the paradigm for the later ultrasonic delay lines which recycled data in the form of sound waves. Ditto for drum & disk drives, which recycled data on magnetic "tapes". At 06:48 PM 11/8/2011, Stuart Anderson wrote:
A new BBC documentary has been screened on Bletchley Park Code Breakers, on how the Nazi Lorenz cipher was cracked. (Lorenz has been described as Hitlers 'Blackberry' - not to be confused with Enigma). The doco provides new archival material on the contributions of William Tutte and Tommy Flowers. Tutte with his reconstruction of the Lorenz cypher/decypher mechanism, based only on intercepted messages and later his statistical algorithm which required a computer. This was Tommy Flowers contribution. He invented and constructed of the worlds first electronic programmable computer, 2 years before ENIAC, to run Tutte's algorithm. The rest as they say is history, but for most of the last 60 years this history has been kept secret.
Some secrets have been kept for too long.
http://www.youtube.com/watch?v=bMu8UiHJHgs
Stuart