![]() ![]() Shown in the illustration are just a few of the keys and lit letters, and only a few of the wires in the rotors. To make the Enigma easy to use, a circuit including a battery, keyboard, and light-up letters for a display were added. 17,576 x 60 = 1,054,560 Enigma Machines With Only Rotors 3-rotor Enigma circuit 5 x 4 x 3 = 60Īnd since there were 17,576 possible paths a letter could take through the rotor, that gives 1,054,560 possibilities altogether. That gives 60 possible ways to choose the three rotors being used for a message. Prior to use, for a three-rotor machine, three rotors would be selected from however many rotors were available to choose from.Īssuming we were trying to decrypt an army message, we’d have a choice out of five rotors to use for the left one, then a choice out of the four remaining rotors to use for the middle one, and then a choice out of three for the right one. And to add even more possibilities, up to eight rotors were made altogether, each with their own wiring and Roman numerals: IV, V, VI, VII and VIII. The German Army and Air Force used five and the Navy used up to eight. ![]() Rotor II might be the left one, with rotor III in the middle and rotor I on the right. But to further complicate things for anyone who might have such a machine and be trying to decrypt a message, the rotors are allowed to be moved around before use. They’re therefore given names using Roman numerals: I, II and III. 26 x 26 x 26 = 17,576Īs we said, each rotor is wired differently. The total possible number of paths for A to take through all three rotors is therefore 17,576. And then 26 more possible paths through the third one. But once we’ve followed the wire through the first rotor, there are now 26 possible paths through the second rotor. How many possible paths does that give us through three rotors for the letter A? Keep in mind that each rotor can be turned to any position. That means that for the first rotor there are 26 possible paths through it for A. As shown in the photo from inside an actual Enigma, each rotor also has an attached alphabet ring that turns with the rotor and is used to set the initial position of the rotor. In some Enigma machines there were three rotors, and the most used was eight. And internally, each of the rotors are wired differently i.e. In the rotor, each wire has external contact points on either end. That allows some multiple of these rotors to be put side-by-side, with adjacent contacts touching. Follow the diagram above and you notice that the first Z came from the H, but the Z in the fourth position came from the K. Repeating this step of substitution followed by turning the rotor for each letter, HACKADAY becomes ZJGZLVFA. After one turn, A would now be substituted with whatever Z formerly was, namely J. By turning the rotor while leaving the letters stationary, the connections between letters change. One way to easily implement that, and it’s the way it’s done in the Enigma, is to embed all that wiring in a wheel/rotor. ![]() And even better, if they change each time a letter is encoded. An improvement would be for all those pairings to change. The ability to change the mapping is important because once someone deduces that G is the substitution for A, they’ll know that’s true for every G in the ciphertext. Rotating substitution cipher Enigma rotor wiring But those lines can be wires, electrically connecting each pair, which opens up the possibility of easily changing how the substitution is mapped through to the ciphertext. We could redraw the cipher as two alphabets with letters in alphabetical order, and draw lines between the paired letters. Adding Rotors Simple substitution cipher with wires Let’s take this further like the Enigma machine does. To decrypt it we do the reverse, look for each letter in the bottom row and substitute with the corresponding letter in the top row, getting HACKADAY. Similarly, looking for the A in the top line, we see we should substitute it with a G. ![]() Using the above cipher we look in the top line for the H and we substitute the letter below it, a Z. Let’s say we want to encrypt the word Hackaday. Most have seen how to encrypt messages using a simple cipher like this. Most recently the story of how it was broken was the topic of the movie The Imitation Game. Possibly the greatest dedicated cipher machine in human history the Enigma machine is a typewriter-sized machine, with keyboard included, that the Germans used to encrypt and decrypt messages during World War II. It’s also one of the machines that the Polish Cipher Bureau and those at Britain’s Bletchley Park figured out how to decipher, or break. But it’s really quite simple. The following is a step-by-step explanation of how it works, from the basics to the full machine. To many, the Enigma machine is an enigma. ![]()
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