In thehistory of cryptography, theKryha machine was a device for encryption and decryption, appearing in the early 1920s and used until the 1950s. The machine was the invention ofAlexander von Kryha [de] (born 31.10.1891 inCharkow,Russian Empire, committed suicide inBaden-Baden in 1955).[1] During theSecond World War, Kryha worked as an officer for the GermanWehrmacht.[1] There were several versions; the standard Kryha machine weighed around five kilograms, and was totally mechanical. A scaled down pocket version was introduced later on, termed the "Lilliput" model.[2] There was also a more bulky electrical version.[3]
The machine was used for a time by the German Diplomatic Corps, and was adopted byMarconi inEngland.[3]
The machine consisted of twoconcentric rings each containing analphabet.[3] The inner alphabet was stepped a variable number of places by pushing a lever. In operation, the user would encrypt by finding theplaintext 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.[3] When the lever was pressed, the inner ring would step, causing the relationship between the two alphabets to change. The stepping was irregular and governed by the use of a disk with a number of sectors, each containing a number of teeth.[3]
The security of the machine was evaluated by the mathematicianGeorg Hamel, who calculated the size of thekey space.[2] The US Army was also contacted to see if they would be interested in using the machine, and were persuaded to accept a challenge message to evaluate the security of the device. The challenge message, 1135 characters long, was solved byWilliam Friedman, assisted bySolomon Kullback,Frank Rowlett andAbraham Sinkov, in 2 hours and 41 minutes.[1]
Media related toKryha at Wikimedia Commons
