In 1918, German inventor Arthur Scherbius and Richard Ritter founded an innovative engineering firm. To replace the inadequate system of cryptography used in the First World War, Scherbius developed an electrical version of cipher disc. This device, called Enigma became one of the most fearsome systems of encryption in history.

The Enigma machine was contained in a compact box measuring 34x28x15 cm, but it weighs a hefty 12kg. The following figure shows an Enigma machine with outer lid open, ready for use. The keyboard is where the plaintext letters are typed in and the lamp board displays the ciphertext. Below the keyboard is the plug board. Back in those days, an individual unit would cost as much as S$60,000 in today’s prices.

The German military believed that the Enigma machine offered the best solution for communication security. They improved on the original Enigma by introducing more rotors and specifying the minimum number of plug board connections, and maximum size of message to be transmitted. By 1925, Scherbius began mass-producing Enigmas, which went into military service the following year, and were subsequently used by the government and by even state-run organization such as the railways. The German military would deploy over 30,000 Enigma machines for their secure communications.

For more details on the history and description of the Enigma, do check out The codebook. http://www.simonsingh.com

The technical specifications described in this section are used to generate the cipher challenge. For more technical information and understanding on the working of the Enigma, please refer to http://www.codesandciphers.org.uk/enigma/

These are the permutations performed by the rotors:

Reflector

The reflectors of the Enigma can be specified most easily in the cycle representation:

Stepping mechanism

The rotors also differed in where they had the effect of knocking on the slower-moving rotor to the left. These points can be specified in terms of which letter appears in the window when the knock-on occurs:

Example

Check out Andrew Lauwers’ web site and try out the Enigma 2.0 emulator.

http://www.users.globalnet.co.uk/~andlaw/engindex.htm

You may wish to try the following example.

Reflector B

Rotors: I (Left) II (Middle) III (Right)

Ring Setting: 1 2 3

Position: A B C

Plugboard: A-B, C-D, E-F

To reduce the complexity, we removed all the spacing in the plaintext. You may wish to know that the German in fact places "X" to denote as space. Enigma only accepts 26 upper case alphabets. There is no numeric or punctuation.

The actual German Enigma machine uses 3 out of 5 rotors. There is also reflector B and C to choose from. The German military insists on having plugs of 7 to 10 pairs and messages should be short, around 200 characters.

In this challenge, we really simplified the German Enigma machine. Imagine that you managed to salvage a live Enigma machine from a German U-boat. The machine uses Rotor I,II,III and reflector B, however the ring settings, positions and plugs had all been reset. Fortunately, you managed to recover 800 worth of ciphertext characters on a single transmission due to the signaler failing to follow operating procedures.

Hint:

1. Intelligence gathered says that at most 3 pairs of plugs are used.

2. Plaintext is based on English text & spaces are omitted.

You are to decipher the ciphertext and recover the ring settings, rotor positions, and plugs connections.

Reflector B

Rotors: I (Left) II (Middle) III (Right)

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