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15 November 2007, 13:51

Who will defeat Colossus?

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Starting this Thursday at 09:00 UTC, Radio amateurs and cryptologists are being challenged to decode encrypted radio messages generated by a Lorenz SZ42 cipher machine and sent using the original radio protocol from WWII. Those taking part in the cipher event will compete against a rebuild of the computer used to crack enciphered messages sent by the German high command 63 years ago. The competition, in which enthusiasts can participate using a virtual Colossus Mark II and a virtual replica of the teleprinter, is being held to celebrate the completion of the Colossus Mark II rebuild in the British Computer Museum in Bletchley Park. Representatives of the Heinz Nixdorf Museumsforum (HNF) in Germany will prepare and transmit the ciphertexts.

Messages of four different levels of cryptanalytic difficulty will be transmitted using various communication channels. The first message will be sent using the standard radio protocol of the time by Rudolf Staritz, head of German military counter-intelligence under Admiral Canaris. 24 hours later, the encrypted texts will be sent using the radio teletype protocol used by radio hams today. 48 hours after the initial transmission, the encrypted text will be published on the Internet. Over 50 radio hams in Germany and the UK are taking part in the cipher event, for which a host of special permits had to be applied for. While anyone can encrypt and send an email just by clicking a mouse, sending encrypted radio messages is governed by strict official regulations. There will be a videofeed of events as they occur on the HFN website at

(Detlef Borchers)


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