Kryha Crypto Machine

Developed in the 1920s, the Kryha was a clockwork-driven mechanical device for encryption and decryption. In 1933, the U.S. Army was asked to evaluate the security of the device. The challenge message, 1135 characters long, was deciphered by William Friedman, assisted by Solomon Kullback, Frank Rowlett and Abraham Sinkov, in 2 hours and 41 minutes.