Virtual Lorenz SZ40/42 3D

A 3D virtual simulation of the German World War II cipher attachment

New! Released 12th December 2022

Find Out More Run Virtual Lorenz 3D Try Paper Lorenz

What is a Lorenz SZ42?

During World War II, the German High Command required a fast and secure way of transmitting messages between themselves and the army commanders out on the battle fronts. C. Lorenz AG in Berlin created a set of cipher attachment machines, the Lorenz SZ40, SZ42A and SZ42B, which could encode messages directly from a teleprinter and transmit them via radio to a duplcate machine at the receiving end where the original message would be decoded automatically.

This website has an online simulation of the Lorenz machines so you can actually encipher and decipher secret messages, exactly as they did during the war.

What do I need to know to run it!
Instructions for use

Looking around

Look around by left-clicking and dragging on the background. Right-click (or shift-click) will move the camera and middle-mouse will zoom.

Alternatively, you can use the Change View buttons below to move to pre-set camera positions.

Click or swipe rotors and switches

Try click/dragging up and down on the rotors or pressing the teleprinter keys.

Try opening the cover of the Lorenz by clicking the lock image then change the switches on the rotors.

Prefences and example messages

Use the Prefs menu to change the model, settings etc.

Attempt to connect to other users across the internet or try to decipher some example pre-defined encrypted messages.


Check out the tutorials in the top menu on the Lorenz emulator page.

These will give you an idea on how the Lorenz SZ was used to send and receive messages or to set the machine for use.

What does it do?

Credits and links

A number of people I need to say thanks and tip my hat to... .. The National Museum of Computing where my obsession was sparked! .. Bletchley Park

Heinz Nixdorf MuseumsForum .. Heinz Nixdorf MuseumsForum

The Bill Tutte Memorial Fund .. "Bill Tutte achieved one of the greatest intellectual feats of World War Two by breaking the extremely complex Lorenz code without ever seeing the machine that generated it."

Captain Jerry Roberts and all the codebreakers in the Testery. Without these people's code breaking skills and their daily breaking of the Lorenz wheels, Colossus would have been unable to function.

Frode Weierud's .. for his assistance answering questions and especially his site's Lorenz operating manuals!

Let me know what you think!

Have I got something wrong, it doesn't work quite correctly on your computer or maybe you just want to say hi - find me on Twitter or check my Facebook or Twitter pages

Martin Gillow