![]() At the end of the series of rotors, a “reflector” passes the signal back through the rotors, where it then illuminates one of the letters on the Enigma’s display. When a key is pressed, a corresponding electrical signal is fed to the first rotor, whose output is used as the input for the next rotor. This acts as a basic substitution cipher, so that A becomes H, for instance. Each rotor hard-wires pairs of letters together in its own unique pattern. This made it impossible to fit the plugboard into place until I provided additional clearance by extending the front of the case with some spare beams of basswood.Īt the core of an original Enigma machine lies a set of three or four rotors. Unfortunately, when I tried to fit everything into the case, I discovered that the plugboard cable connector was pressing against the daughterboard that holds the Arduino Mega underneath the top panel. Initially-taking my lead from online pictures of some fully assembled kits-I built my case with the intent of mounting the plugboard immediately in front of the top plate. ![]() I built mine from basswood, making it a few centimeters taller than it needed to be so that I could have a space for storing unused plugboard cords underneath. The Mark 4 does not come with a case, so I had to make my own (although you can now buy hand-built cases from S&T Geotronics for an additional $350). Once the various mother- and daughterboards were populated and connected together, I downloaded the software from the Open Enigma website and installed it via a USB cable connected to the Arduino Mega. I found that prizing the contacts a little off the body of each LED made them much easier to solder to the right spot on the motherboard. These are small surface-mount LEDs and can easily slip out of place during assembly. The only truly fiddly part of this stage of construction was soldering the LED lights that form the Enigma machine’s alphabet display. I built a simple wooden case to house the circuitry (bottom). Spinning Electrons: The keyboard and displays of the Enigma are replaced by buttons and LEDs (top), while its mechanical rotors are simulated by an Arduino Mega (blue and white circuit board, middle). Still, there was nothing that couldn’t be figured out with a little thought. I built the plugboard version for maximum verisimilitude and ease of use, but users of kits without this panel can program plugboard settings into the Arduino software.Īssembling the Mark 4 was mostly a straightforward exercise in soldering, but there were a few places where the instructions were a little unclear, such as how to wire up the battery pack or how to hold the faceplate of the plugboard in place. It’s available in three versions-one that has just the printed-circuit boards and basic components for US $200, one that includes a top panel and an Arduino Mega for $300, and a version that also includes a plugboard front panel for $425. ![]() The kit-called the Enigma Mark 4-was created by S&T Geotronics as an open-source project with development funded by a Kickstarter campaign. But now there’s a middle ground: a hardware kit that duplicates the physical operation of the Enigma’s keyboard, display, and plugboard while replacing the rotating metal discs at the machine’s heart with an Arduino Mega microcontroller. So the only alternative for those wishing to get to grips with this machine-and to better understand the mathematical, engineering, and operational feats that defeated it-has been to use one of a number of software emulators. Used by the German military to encode communications in the run-up to and during World War II, the Enigma has achieved a mythic quality in computing history-the Medusa slain by the hero Turing with the new weapon of digital logic.Ĭonsequently, original Enigma machines are now collector’s items that sell for tens of thousands of dollars. Nearly a century after its invention, the electromechanical Enigma cipher machine still strikes a deep chord among the digerati.
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