TNMoC - Cipher Challenge!


The Cipher Event – Recreating the Past

Take part and challenge Colossus!

The Cipher Event - Recreating the Past

On 15 and 16 November 2007 we shall celebrate the completion of the Colossus Mark 2 rebuild at Bletchley Park and recreate cryptographic history when an international team will:

1. Prepare three separate (secret) texts in German (the challenge plaintexts);

2. Encipher each of those plaintext messages using the Lorenz SZ42 cipher and prepare three paper tapes (the challenge ciphertexts);

3. Transmit each of those ciphertexts in turn using amateur radio operators in Germany;

4. Intercept the ciphertexts at a replica ëYí station in the UK;

5. Interpret the ciphertexts using an original undulator and transfer those interpreted ciphertexts on to paper tape;

6. Load the paper tape ciphertexts on the Colossus Mark 2 rebuild in Bletchley Park Block H. Run the Colossus to recover the Lorenz machine wheel settings used to encipher the plaintext;

7. Recover the secret plaintext messages;

8. Validate the result.

At the same time as the international team receives the enciphered messages, radio amateurs around the world will be able to receive the same radio broadcasts and try their hand at decrypting it. It will be fascinating to see who completes the job first!

Encipher the Secret Message

Representatives from Heinz Nixdorf MuseumForum in Paderborn, Germany under the guidance of Norbert Ryska will prepare the challenge plaintexts (in German).

Transmit the Ciphertext

Radio amateurs at the radio station DL0HNF located in the Heinz Nixdorf MuseumForum, Paderborn will transmit the challenge ciphertexts. Heinz-Peter Bleier will lead the team and plans to operate a special event station with a dedicated callsign specifically for the purpose.

Intercept the Ciphertext

The Paderborn transmissions will be intercepted by two teams at Bletchley Park ñ the first will be led by John Housego and comprise members of the Milton Keynes Amateur Radio Society operating amateur radio station callsign GB2BP. They will use current technology receivers and signal capture methods.

The second team will be led by John Pether who will use the same type of equipment as used in the ëYí (intercept) station in Knockholt in WWII. This equipment includes AR88 receivers with undulators connected for hardcopy output on strip tape.

Interpret the Ciphertext

John Pether's team will interpret the output of the undulators by hand and punch paper tape directly for loading on to the Colossus Mark 2.

Run the Colossus Mark 2

Tony Sale and his team will load the paper tape containing the ciphertext on to the Colossus and run it to find the Lorenz machine wheel settings.

Recover the Plaintext

Once the Colossus has reported the wheel settings, Tony and his team will use the Tunny simulator to recover the plaintext (the TUNNY rebuild is not yet complete).

Validate the Result

Once the plaintext has been recovered, members of the MKARS plan to email and transmit the plaintext back to Germany using RTTY for validation and scoring.


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