In the

history of cryptography Cryptography, the use of codes and ciphers, began thousands of years ago. Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple m ...

, 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 The Russian Empire was an empire that spanned most of northern Eurasia from its establishment in November 1721 until the proclamation of the Russian Republic in September 1917. At its height in the late 19th century, it covered about , roughl ...

, committed suicide in

Baden-Baden Baden-Baden () is a spa town in the states of Germany, state of Baden-Württemberg, south-western Germany, at the north-western border of the Black Forest mountain range on the small river Oos (river), Oos, ten kilometres (six miles) east of the ...

in 1955). During the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, Kryha worked as an officer for the German

Wehrmacht The ''Wehrmacht'' (, ) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the German Army (1935–1945), ''Heer'' (army), the ''Kriegsmarine'' (navy) and the ''Luftwaffe'' (air force). The designation "''Wehrmac ...

. 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. There was also a more bulky electrical version. The machine was used for a time by the German Diplomatic Corps, and was adopted by Marconi in

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

Operation

The machine consisted of two

concentric In geometry, two or more objects are said to be ''concentric'' when they share the same center. Any pair of (possibly unalike) objects with well-defined centers can be concentric, including circles, spheres, regular polygons, regular polyh ...

rings each containing an

alphabet An alphabet is a standard set of letter (alphabet), letters written to represent particular sounds in a spoken language. Specifically, letters largely correspond to phonemes as the smallest sound segments that can distinguish one word from a ...

. The inner alphabet was stepped a variable number of places by pushing a lever. In operation, the user would encrypt by finding the

plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted. Overview With the advent of comp ...

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. 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.

Cryptanalysis

The security of the machine was evaluated by the mathematician Georg Hamel, who calculated the size of the key space. 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 William Frederick Friedman (September 24, 1891 – November 2, 1969) was a United States Army, US Army cryptography, cryptographer who ran the research division of the Army's Signal Intelligence Service (SIS) in the 1930s, and parts of its foll ...

, assisted by

Solomon Kullback Solomon Kullback (April 3, 1907August 5, 1994) was an American cryptanalyst and mathematician, who was one of the first three employees hired by William F. Friedman at the US Army's Signal Intelligence Service (SIS) in the 1930s, along with Fr ...

Frank Rowlett Frank Byron Rowlett (May 2, 1908 – June 29, 1998) was an American cryptologist. Life and career Rowlett was born in Rose Hill, Lee County, Virginia and attended Emory & Henry College in Emory, Virginia. In 1929 he received a bachelor's degr ...

and

Abraham Sinkov Abraham Sinkov (August 22, 1907 – January 19, 1998) was a US cryptanalyst. An early employee of the U.S. Army's Signal Intelligence Service, he held several leadership positions during World War II, transitioning to the new National Security Ag ...

, in 2 hours and 41 minutes.

References

* Alexander von Kryha, "Coding machine", * 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.

Operation

Cryptanalysis

References

External links