Cyclometer

This article is about the cryptologic device. For the device used in cycling, see cyclocomputer. "Cyclometer" also means a person who works either on the classic circle-squaring problem or on the geometry of circles.
Cyclometer, devised in the mid-1930s by Rejewski to catalog the cycle structure of Enigma permutations. At top are the two rotor banks, one with lid open; below is the rheostat at left, and at right the array of lamps and switches labelled with corresponding letters.

The cyclometer was a cryptologic device designed, "probably in 1934 or 1935," by Marian Rejewski of the Polish Cipher Bureau's German section (BS-4), to catalog the cycle structure of Enigma permutations, thereby facilitating the decryption of German Enigma ciphertext.[1]

With Rejewski's later cryptologic bomb, it can be viewed as a predecessor to the Bombe that was to help break Enigma ciphers later in the war at Bletchley Park in England.

Using drawings made by Rejewski, Hal Evans and Tim Flack at the Department of Engineering, University of Cambridge, in 2019 constructed a working version of the cyclometer.[2]

  1. ^ Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", p. 242.
  2. ^ Evans, Henry A.(2019): Recreation of the Polish Cyclometer and its role in breaking Enigma. MEng dissertation, University of Cambridge [1]