Engineers from the UK’s Government Communications Centre (HMGCC) are using 3D printing to recreate the Lorenz SZ42, an “unbreakable” cipher machine used by Hitler and the German Army during World War II. Only four of the machines still exist. During the Second World War, various versions of the Lorenz cipher were used by the German Army to encrypt strategic communications. These machines, each of which contained 12 wheels with a different number of pins, were attached to standard teleprinters in order to turn readable German text into code.