Portex

A Portex (with the lid open) at an exhibition in Bletchley Park (2005). The eight rotors arranged next to each other are clearly visible.

Portex (rear) with additional roller box in the Royal Signals Museum (2005)

The Portex (also: BID / 50/1 ) was a British rotor cipher machine that was used by the British Secret Service between 1945 and 1955, during the early days of the Cold War . The Canadian army still used them in the early 1960s.

Principle and structure

The principle of the Portex is similar to the Enigma used by the German Wehrmacht in World War II . However, it is much more advanced and, in contrast to the only three or four rollers on the German machine, uses eight rotors arranged next to one another . This results in a significantly higher combinatorial complexity and a significantly improved cryptographic security. In addition, the Portex uses an irregular rotation of the rotors and thus avoids a significant cryptographic weakness of the Enigma.

Exhibits

Only a few surviving copies of the Portex cipher machine are known. An exhibit is on display at the Royal Signals Museum at Blandford Camp at Blandford Forum in the English county of Dorset . Next to the encryption machine is a box with nine individual Portex rotors.

Web links

Commons : Portex - album with pictures, videos and audio files

Crypto Museum , accessed May 18, 2017.
Jerry Proc , accessed May 18, 2017.

Individual evidence

↑ ^a ^b Jerry Proc , accessed May 18, 2017.

[jproc.ca-1] Jerry Proc , accessed May 18, 2017.