Kryha
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 Template:Ill (born 31.10.1891 in Charkow, Russian Empire, committed suicide in Baden-Baden in 1955).[1] During the Second World War, Kryha worked as an officer for the German Wehrmacht.[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 by Marconi in England.[3]
Operation
The machine consisted of two concentric rings each containing an alphabet.[3] 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.[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]
Cryptanalysis
The security of the machine was evaluated by the mathematician Georg Hamel, who calculated the size of the key 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 by William Friedman, assisted by Solomon Kullback, Frank Rowlett and Abraham Sinkov, in 2 hours and 41 minutes.[1]
References
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- Alexander von Kryha, "Coding machine", U.S. patent 1744347
- Alan G. Konheim, Cryptanalysis of a Kryha Machine, EUROCRYPT 1982, pp49–64.
- Cipher A. Deavours and Louis Kruh, "Machine Cryptography and Modern Cryptanalysis", Artech House, 1985, chapter IV.
External links
- Template:Sister-inline
- Jerry Proc's pages on the Kryha: Standard, Electrical and Lilliput.
- Standard Kryha: Machine cover open and Machine cover closed
- Nick Gessler's page on the Kryha: Photographs
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