![]() The second important feature is that a letter can never be encrypted as itself. This is very important in terms of ease of use because it means the setup for encryption and decryption are the same. This always happens because the reflector swaps letters. That is, if A is encrypted as B, then B is encrypted as A. Note that the reflector serves two very important roles. Thus, the levers are to the left of a rotor rather than the to the right of a rotor. Note, the levers are at the back of the rotors so this shows the action from the rear of the machine. This is easier to see in action in the video below. Since rotor 2 is not moving at every step this produces an additional stepping of rotor 2. When lever 3 hits the notch on rotor 2, it moves rotor 2 and rotor 3. Lever 3 is similar to lever 2 but located between rotor 2 and rotor 3. Rotor 1 is moved by lever 1 at every step, so this additional effect of movement by lever 2 is not noticable. When engaged it moves rotor 1 (via the notch) and rotor 2 (via the gear). This lever becomes active only when it engages the single notch on rotor 1. It is wider than lever 1, and is connected to both a gear with 26 teeth and the edge of rotor 1 which has a notch in only one position. The second lever is located between the first and second rotors. Thus, this lever moves the rotor to the next node every time a letter is pressed on the keyboard. It is connected to a gear on the rotor with 26 teeth. The first lever is on the outside of the rotor 1 (to the right of rotor 1 if viewed from the front of the machine). ![]() Pressing a letter on the keyboard moves three levers connected to each rotor. The mechanics of the stepping action are very interesting and sometimes produced an unexpected stepping of the middle rotor. ![]() Note this stepping action occurs when the key is pressed and before the current is sent through the circuit. The important part of the scrambling unit is that every time a letter is pressed on the keyboard a stepping action changes the location of at least one rotor, so that the next letter is encrypted in a very different way. Enigma operators would record this letter as the ciphertext for the plaintext letter they entered on the keyboard.įigure 4.2.7. Pressing the letter on the keyboard initiated a current which traveled through the keyboard, plugboard, and scrambling unit to light up a letter in the lampboard. The last part of the enigma machine was the display board or lampboard. More details on the scrambling unit is below. For the three rotor machines, the reflector was a fixed part of the machine and could not be changed. The reflector consisted of 26 nodes with wires that swapped thirteen pairs of letters and sent them back through the rotors in reverse. (Special fourth rotors and thinner reflectors were designed to take the place of the entire reflector.) For four rotor machines, three of the rotors could be placed in any order, but the fourth rotor was limited. For three rotor machines, the rotors could be arranged in any order. Each rotor was then rotated to a given starting letter. The rotors were connected together and placed into the machine as a unit of three or four rotors. This doesn't create additional initial settings, but rather disguises the displayed rotor setting.įigure 4.2.6. The letters for all of the rotors in the machine is often called the indicator setting. Each rotor would be placed into the machine with one of these numbers of letters showing in a display board. This clip specifies the ring setting of each rotor. This metal ring could be shifted relative to the wiring by means of a clip. On the left hand side of each rotor there is a metal ring with either the numbers (1-26) or the letters (A-Z). On the right hand side of each rotor was a cogwheel with 26 teeth. For detailed images of how to wire a rotor, see. This wiring created a one-to-one switching of letters in the alphabet (that is, a permutation of the alphabet). These two sets of nodes have wires connecting one to the other. The Scrambling Unit of a 3-rotor Enigma Machineįor the scrambling unit portion of the Enigma machine, if viewed from the front of the machine, the current passes throughĮach rotor consisted of 26 nodes on each side (one side has pin contacts and the other side has flat contacts). Probability, Permutations and Combinationsįigure 4.2.5.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |