Cpp-Enigma is a C++11 library for simulating the Enigma machines used by the German armed forces (Wehrmacht) during World War 2. Cpp-Enigma makes it possible to both encrypt and decrypt messages that can be sent to, or received from, actual Enigma machines used by the German army (Heer), air force (Luftwaffe), and navy (Kriegsmarine).

It is my hope that library will be useful to Enigma enthusiasts, historians, and students interested in cryptography.

Cpp-Enigma is basically a C++11 port of my Py-Enigma library, which is written in Python 3. Cpp-Enigma was created when I started doing performance intensive hill-climbing searches for Enigma keys. The Python library is very convenient for quick experiments and simple brute force attacks when most of the key parameters are known. Cpp-Enigma is for when you need much greater performance, such as a cipher-text only attack involving hill-climbing.

This example shows how the library can be used to decode a message using the procedure employed by the German army:

#include <iostream>
#include <string>
#include "machine.h"

using namespace enigma;

int main()
{
   // setup machine according to specs from a key sheet:

   enigma_machine em({"II", "IV", "V"}, {1, 20, 11}, "B",
         "AV BS CG DL FU HZ IN KM OW RX");

   // set initial rotor starting position
   em.set_display("WXC");

   // decrypt the message key
   const std::string msg_key = em.process_text("KCH");

   // decrypt the ciphertext with the unencrypted message key
   em.set_display(msg_key);

   const std::string ciphertext("NIBLFMYMLLUFWCASCSSNVHAZ");
   const std::string plaintext(em.process_text(ciphertext));

   std::cout << plaintext << std::endl;
   return 0;
}

This program prints:

THEXRUSSIANSXAREXCOMINGX

Cpp-Enigma is written in C++, and uses features found in the C++11 standard. The code was developed on GCC 4.6.3.

Cpp-Enigma ships with SCons build files.

Cpp-Enigma's unit tests require the CxxTest unit test framework. This is only required if you plan on running or modifying the tests.

Cpp-Enigma has no other requirements or dependencies.

You may download a tarball or .zip file of the latest code using the "get source" link on the Cpp-Enigma Bitbucket page. Alternatively if you use Mercurial, you can clone the repository with the following command:

$ hg clone https://bitbucket.org/bgneal/cpp-enigma

Once you have obtained a copy of the source and installed SCons the software can be compiled on GCC with:

$ scons

If you have CxxTest installed and configured to work with SCons, you may run the unit tests with:

$ scons check

I have not currently compiled the code on other compilers or environments. Patches or pull requests are welcome.

Currently there is no documentation for Cpp-Enigma. However the design and API is almost identical to Py-Enigma, which is well documented. I will quote from the Py-Enigma README file below:

The latest documentation is available at Read the Docs. There you can browse the documentation online, or download it in a variety of formats.

Sources for the documentation are also included in Sphinx format. If you install Sphinx you can generate the documentation in several output formats.

Between the Python docs and the source code hopefully this will be enough to get you going. Proper documentation may be created in the future. Again, patches and pull requests are welcome.

Support is provided at the issue tracker at the Cpp-Enigma Bitbucket page. If you have general questions or comments, please feel free to email me (address at the top of this file).

And please, if you use Cpp-Enigma for anything, even if it is just learning, please let me know!

This software would not have been possible without the thorough and detailed descriptions of the Enigma machine on Dirk Rijmenants' incredible Cipher Machines and Cryptology website. In particular, his Technical Details of the Enigma Machine page was a gold mine of information.

Dirk has also written an Enigma simulator in Visual Basic. Although I did not look at his source code, I did use his simulator to check the operation of Cpp-Enigma.

I would also like to recommend the photos and video at Dr. Thomas B. Perera's Enigma Museum.

Another good website is The Enigma and the Bombe by Graham Ellsbury.

A nice video which shows the basic components and operation of the Enigma Machine is on YouTube: Nadia Baker & Enigma demo.