M-325

In the history of cryptography, M-325, also known as SIGFOY,^[2] was an American rotor machine designed by William F. Friedman and built in 1944.^[3] Between 1944 and 1946, more than 1,100 machines were deployed within the United States Foreign Service. Its use was discontinued in 1946 because of faults in operation. Friedman applied for a patent on the M-325 on 11 August 1944;^[4] it was and was granted on 17 March 1959 (US patent #2,877,565).

M-325

The M-325 (SIGFOY) cipher machine was inspired by the German Enigma
Date invented	1944[1]
Type	rotor machine

Like the Enigma, the M-325 contains three intermediate rotors and a reflecting rotor.

Friedman patented the design of the M-325 in US patent #2,877,565.

See also

• Hebern rotor machine
• SIGABA