A tool that Marian Rejewski devised in 1934, together with the cyclometer, as part of his work on Enigma.
The date follows an ABW publication on Rejewski, according to which Rejewski created the card catalogue and the cyclometer in 1934 and, after the method of Enigma encipherment changed, built the cryptologic bomb. The Foreign Intelligence Agency describes the same tools as a response to the increasingly frequent and complex changes the Germans introduced in operating Enigma.1,2
According to the AW, the cyclometer automated calculations concerning the operation of the machine. Alongside these tools, the Polish cryptologists used Różycki's clock method and Zygalski sheets.2
The Cipher Bureau presented the Polish work, including the results obtained with these methods, to French and British delegations at Pyry on 25–26 July 1939. According to Gill Bennett, a historian at the British Foreign Office, this shortened the British attack on Enigma by at least a year.2,3
More in the operation card: Breaking Enigma.
Sources
- Internal Security Agency, Marian Rejewski: in the service of Polish cryptology (ABW Publishing House, Wiązowna 2022, ISBN 978-83-964225-4-5) (in Polish)
- Foreign Intelligence Agency, They broke Enigma (in Polish, with English versions of the biographies)
- Gill Bennett, blog of the UK Foreign Office historians (history.blog.gov.uk), What’s the context? Polish cryptologists reveal they have cracked the Enigma code, 26 July 1939 (26.07.2019)
Checked: 4 November 2026