ENIGMA

This is a small application written in C++ which simulates both the M3 and M4, 3 and 4 rotor variants of the Enigma machine which was utilised by German forces during WWII to encode information. It is a copy of the Python version found here.

Prerequisites

Enigma uses the Boost C++ library which should be installed first. It also makes use of a custom logging class that I have written and is automatically fetched and installed.

App

Included within this package is a demo application which provides a terminal based user interface. The application is built with CMake>=3.10:

mkdir build
cd build
cmake ..
cd ..
./applications/bin/enigma_app

Running the app will allow the user to specify settings such as the key, the rotor type choice (unique numbers from 1-8), and rotating the internal wiring within each rotor (Ringstellung). The user enters then enters their input next to the INPUT: prompt. The machine can be reset at any point to the start settings for decoding using the reset command within the app. Quit the application using the quit command.

Custom Machine

To create a new instance of Enigma the default can be used which is an M3 instance with pre-selected rotor arrangement and reflector choice, or all settings can be chosen by the user. Note as with the machine itself, one of the 8 numbered rotor types may only be selected once.

#include "Enigma.hxx"

#include <vector>
#include <string>
#include <iostream>

int main(int argc, char** argv)
{
    const std::vector<int> my_rotor_list = {1, 4, 6, 4}; // 3 or 4 of 1,2,3,4,5,6,7,8
    const char my_reflector = 'B';                       // 'B' or 'C'
    const std::string machine_type = "M4";               // 'M3' or 'M4' (should match rotor list)
    const bool debug_mode = false;                       // Run Enigma in debug mode

    Enigma* enigma = new Enigma( my_rotor_list, my_reflector, machine_type, debug_mode );

    enigma->ringstellung("right", 2);   // Perform an internal wire rotation on the right rotor of 2 steps
                                        // for M3 the rotors are {"left", "middle", "right"}
                                        // for M4 the rotors are {"left", "middle left", "middle right", "right"}
    
    const std::string key = "NERO";
    const std::string phrase = "NOBODYEXPECTSTHESPANISHINQUISITION";

    enigma->set_key(key);
    
    const std::string cipher = enigma->type_phrase(phrase);

    std::cout << phrase << " -> " << cipher;

    return 0;
}

Unit Tests

For testing Enigma during the development Google Test has been included within the build procedure when running CMake, to launch the included unit tests run the executable within the tests folder:

./tests/bin/Enigma-unit_tests