thumbnail|280px|The standard Kryha machine weighed around five kilograms and was totally mechanical. While the machine achieved a measure of popularity, its security was relatively weak; US cryptanalyst [[William Friedman reported that he solved the device within 2 hours and 41 minutes.]]
In the history of cryptography, the Kryha machine was a device for encryption and decryption, appearing in the early 1920s and used until the 1950s. The machine was the invention of (born 31.10.1891 in Charkow, Russian Empire, committed suicide in Baden-Baden in 1955). During the Second World War, Kryha worked as an officer for the German Wehrmacht. There was also a more bulky electrical version. The inner alphabet was stepped a variable number of places by pushing a lever. In operation, the user would encrypt by finding the plaintext letter on one ring (usually the outer ring), and reading the corresponding letter on the other ring; this was then used as the ciphertext letter.