ECM Encryption Machine Simulation

This page launches a javascript simulation of the U.S. Military's World War 2 vintage ECM/SIGABA encryption machine.

• Run the simulator (opens a new window.) At startup, the simulator is set to encipher. You can either click the virtual keyboard or use your computer keyboard to enter plain text. The text that you type (plaintext) will appear in the "keyboard display" window. The enciphered text will appear in the "paper tape" windows at the top right. You can use the "copy" icons at the right of each window to copy its contents. If you reset the machine and set it to "decipher," You should be able to type in your previously encrypted text and get your original plaintext back.

The ECM II, known by the Army as SIGABA, was the only cipher machine to remain completely unbroken by the enemy in World War II. The ECM II was a rotor machine, similar in concept the the German Enigma, but used 10 rotors instead of 4, and the cipher rotors stepped in a very complex pattern, determined by a set of "control" rotors. This arrangement made the number of possible "alphabets" astronomical. The ECM II was used by the U.S. from 1941 until 1959, when it was retired not because it was insecure, but because it was too slow for the growing needs of naval communications.

Links to additional information on the ECM/SIGABA cipher machine

• If you're near Albany NY, you can see one of the very few remaining ECM II cipher machines by visiting the U.S.S. Slater. The ECM is located in the radio shack, where it was kept in a locked safe inside a locked coding room. The Slater's machine is on loan from the National Cryptological Museum. at the NSA.
• USS Pampanito ECM Page Background on the simulation, together with a link to the original Java Applet version and its source code.
• Description of the ECM Mark II cipher machine, with photos of the rotors and other components. From the USS Pampanito website.
• The SIGABA / ECM II Cipher Machine: "A Beautiful Idea" a 2015 book by Timothy Mucklow, of the Center for Cryptologic History, about the ECM/SIGABA cipher machine. Distributed for free by the NSA.
• Wikipedia article on the ECM/SIGABA encryption machine