Typex

In the history of cryptography, Typex (alternatively, Type X or TypeX) machines were British cipher machines used from 1937. It was an adaptation of the commercial German Enigma with a number of enhancements that greatly increased its security. The cipher machine (and its many revisions) was used until the mid-1950s when other more modern military encryption systems came into use.

Description

Like Enigma, Typex was a rotor machine. Typex came in a number of variations, but were five-rotor machines (as opposed to three or four in the Enigma) with a non-rotating reflector. Typically the first two rotors were stationary during encipherment, although they could be set by hand. These additional stationary rotors provided a similar sort of protection to that of the Enigma's plugboard (but without the weakness of being reciprocal), which the Typex lacked in early models.

An improvement the Typex had over the standard German Services Enigma was that the rotors in the machine contained multiple notches that would turn the neighbouring rotor.