One of the most ingenious inventions at Bletchley Park was Alan Turing’s Bombe. The Bombe was an electro-mechanical device that replicated the action of several Enigma machines wired together. At each simulated position of the rotors, an electric current would or would not flow in each of the 26 wires, and this would be tested in the bombe's comparator unit. For a large number of positions, the test would lead to a logical contradiction, ruling out that setting. If the test did not lead to a contradiction, the machine would stop.
The operator would record the candidate solution by reading the positions of the indicator drums and the indicator unit on the Bombe's right-hand end panel. The operator then restarted the run. Candidate rotor settings were passed along to cryptanalysts for further work.
Turing’s bombe relied on cribs – a section of plaintext that was thought to correspond to the ciphertext. Finding cribs was not at all straightforward; it required considerable familiarity with German military jargon and the communication habits of the operators. However, the codebreakers were aided by the fact that the Enigma would never encrypt a letter to itself. This helped in testing a possible crib against the ciphertext, as it could rule out a number of cribs and positions.
This puzzle uses the same rotor configuration as the first two enigma puzzles. Those configuration are shown in more detail in the graphic below. Figure 1 is an illustration of a rotor setting of "A,A,A". The row labeled "change" describes the action of rotor. For example, if one were to type the letter C, in this position the first rotor would shift the electrical signal forward three spaces to position F. The second rotor would shift the signal forward three more spaces, and so on.
If the operator presses a key, the first rotor (III in this case) would advance once space. The resulting new configuration ("A,A,B") is shown in figure 2. Note that the row labeled "change" has simply shifted one position to the left.
Each rotor has a "notch" in once place which advances the adjacent rotor one position. On the first rotor (rotor III in this case) that notch is at position "V". In other words, when the first rotor advance from V to W, the second rotor will also move forward one position. For this particular puzzle, that is all you need to worry about. The third rotor (rotor I in this case) does not move from its initial configuration).
The following message was encrypted using the standard Army Enigma using the following configuration: Rotor Numbers: I, II, III; Starting Rotor Configuration: Unknown; Plugboard (Stecker): not used.
YJBD ELCZ BCXX PLTM KCVI ICBB EJIS BSNJ XYPS YVCG CREI XLKV BPDF VRBC UZIY CXWD QSUV IKGE HMNI OFVH EYLR GFNB UJMI IIQZ XFCP NISW UTRB AAOQ RXUP ATCX DUCR VFCQ RH
The Point of this puzzle is to find the correct initial rotor configuration from the 17,576 possible initial rotor configurations and to properly account for the movement of the rotors.
You can validate your puzzle solution with certitude.