C-36 (cipher machine)

The C-35 and C-36 were cipher machines designed by Swedish cryptographer Boris Hagelin in the 1930s. These were the first of Hagelin's cipher machines to feature the pin-and-lug mechanism. A later machine in the same series, the C-38, was designated CSP-1500 by the United States Navy and M-209 by the United States military, who used it extensively.

In 1934, the French military approached Hagelin to design a printing, pocket-size cipher machine; Hagelin carved a piece of wood to outline the dimensions of a machine that would fit into a pocket. He adapted one of his previous inventions from three years earlier: an adding device designed for use in vending machines, and combined it with the pinwheel mechanism from a late 1920s cipher machine Hagelin had developed.^[1] The French ordered 5,000 in 1935. Italy and the USA declined the machine, although both would later use the M-209 / C-38. Completely mechanical, the C-35 machine measured 6 × 4.5 × 2 inches, and weighed less than 3 pounds.

A revised machine, the C-36, was similar to the C-35, but had a different distribution of the lugs on the bars. Six C-36 machines were purchased by the Swedish Navy for testing in October 1937. Both machines had five pinwheels with 17, 19, 21, 23 and 25 pins, each individually settable, giving a maximum period of 3,900,225 for the machine. The C-362 revision included a few other improvements, most notably movable lugs instead of fixed.^[2] One variant had a Thai alphabet on the pinwheels, rather than the usual Latin alphabet.^{[citation needed]}

• Andersson, Torbjörn. "The Hagelin C-35/C-36". hem.passagen.se. Archived from the original on 2002-12-02. Retrieved 2005-11-15.{{cite web}}: CS1 maint: unfit URL (link)
• Hagelin, Boris C. W. (1994). Kahn, David (ed.). "The Story of the Hagelin Cryptos". Cryptologia. 18 (3): 204–242. doi:10.1080/0161-119491882865. Retrieved 2024-09-30.
• Kahn, David (1967). "Secrecy for Sale". The Codebreakers. New York: Macmillan Inc. pp. 426–428. ISBN 0-684-83130-9. Retrieved 2024-09-30.

• Deavours, C.A. (1990). "Solution of C-35 Texts with Partial Key". Cryptologia. 14 (2): 162–168. doi:10.1080/0161-119091864869.

• Photos of the C-35/C-36 and its instruction manual at jproc.ca