An Evaluation of Enigma Machine Online Emulators for Teaching and Learning

The Enigma machine is an electromechanical device used to encrypt military messages during World War II. Initially invented as a prototype by Arthur Scherbius in the early 1920s, the Enigma machine evolved into a critical encryption tool for the German Army, as well as for other branches of the German military. The device's ability to encrypt plaintext messages through a series of rotating rotors, plugboard settings, and a reflector mechanism allowed it to generate complex substitution ciphers. These ciphers were considered unbreakable at the time and provided a significant strategic advantage to the German forces. Today, with advancements in technology and the availability of historical information, numerous Enigma machine emulators can be found on the internet. These emulators enable Cyber Security students and enthusiasts to interact with and understand the workings of the Enigma machine. By simulating the encryption process, these online web-based tools offer valuable practical experience in both encrypting and decrypting text, mimicking the operations of the original Enigma machine. However, due to the diverse features and varying levels of accuracy among these emulators, it can be challenging to determine which ones produce correct ciphertexts and faithfully replicate the original machine's functionality. Ensuring the validity of these emulators is crucial for educational purposes. The aim of this study is to evaluate the available online Enigma emulators to identify those that can be recommended for learning and teaching encryption in introductory Cryptography courses. Our evaluation focuses on the accuracy of the emulation and educational value. Additionally, we have developed a new Enigma emulator API as a RESTful service, specifically modelling the military Enigma M3, which was widely used by the German Army. This API serves as a reference implementation, allowing students to build their own Enigma clients and gain hands-on experience in developing a practical and historical cryptographic tool.