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M-94   CSP 488
Strip cipher device - this page is a stub

M-94 was a polyalphabetic manual substitution cipher device for tactical messages, developed around 1917 1 by US Army major Joseph O. Mauborgne, and manufactured by several companies, including Doehler, Reeve and Alcoa. It was introduced to the US Army in 1921 and is based on a 1795 invention by (then) US President Thomas Jefferson. It offers limited cryptographic security.

The device consists of 25 circular discs, each with a different mixed alphabet, placed on a common axle. For this reason, the device is also known as a revolving discs cipher. Each disc has the 26 letters of the Latin alphabet engraved in a different (randomized) order on the outer rim, and is identified by the letter that follows the 'A'.

M-94 was manufactured by several companies. Although the exact procurement figures are unknown, ASA's cryptographer William Friedman reported in 1943, that a total of 9432 units had been manufactured for use by the US Army.

The M-94 was used until approx. 1942, after which was replaced by the M-209 cipher machine. A similar device, issued in 1946 by the Swiss Army, is known as Front-Chiffriergerät (FG).

  1. Somewhere between September 1916 and August 1917 [1].

The principe behind the M-94 seems to have been (re)invented at several moments in history:

  • Thomas Jeferson · 1795
    President of the United States.

  • Etienne Bazeries
    Commandant in the French Army.

  • Parker Hitt
    Captain in the US Army.

  • Joseph O. Mauborgne · 1917
    Major (later: Major General) in the US Army. Chief, Engineering and Research Division, Office of the Chief Signal Officer (afterwards: Chief Signal Officer).
  • 1921 (2000 units)
    Doehler Die Casting Company, New York
  • 1928 (1094 units)
    Reeve Electrical Company,New York
  • ?
  • US Army (M-94) - 1921 onwards
  • US Navy (CSP-488) - 1928 onwards
  • US Coast Guard (CSP-493) - 1939 onwards
  1. ASA Historian AS-13, The History of Army Strip Cipher Devices 1
    SRH-366. July 1934 - October 1947.
    Army Security Agency, Washington (USA), November 1948.

  2. Jerry Proc's crypto pages, M-94 (CSP-488)
    Retrieved May 2018.

  3. Wikipedia, M-94
    Retrieved May 2018.
  1. Declassified 2 March 1987 by Director NSA, per Sec. 3, E.O. 12356.

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