During World War II (1939–1942), the Germans used a machine called the Lorenz SZ42 to send encoded messages. This machine used wheels and switches to create billions of possible combinations. This made the code extremely difficult to crack. However, British codebreaker Bill Tutte was able to figure out how the machine worked. Recently, programmer Martin Gillow created an online replica of the SZ42. The replica lets viewers see how the machine worked. It even allows them to send coded messages.