Perforated sheets
Encyclopedia
The method of Zygalski sheets was a cryptologic technique used by the Polish
Cipher Bureau
before and during World War II
, and during the war also by British cryptologists at Bletchley Park
, to decrypt messages enciphered
on German Enigma machine
s.
The Zygalski-sheet apparatus takes its name from Polish Cipher Bureau mathematician
–cryptologist Henryk Zygalski
, who invented it about October 1938.
's scrambler. Each sheet related to the starting position of the left (slowest-moving) rotor.
The 26 × 26 matrix represented the 676 possible starting positions of the middle and left rotors and was duplicated horizontally and vertically: a–z, a–y. The sheets were punched with holes in the positions that would allow a "female" to occur.
Polish mathematician–cryptologist Marian Rejewski
writes about how the perforated-sheets device was operated:
Like Rejewski
's "card-catalog
" method, developed using his "cyclometer
," the Zygalski-sheet procedure was independent of the number of plugboard
plug connections in the Enigma machine.
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The Cipher Bureau's manual manufacture of the sheets, which for security reasons was done by the mathematician-cryptologists themselves, using razor blade
s, was very time-consuming. By December 15, 1938, only 1/3 of the job had been finished.
On that date, the Germans introduced rotors IV and V, thus increasing the labor of making the sheets tenfold, since ten times as many sheets were now needed (for the now 60 possible combinations of sequences, in an Enigma machine, of 3 rotors selected from among the now 5).
On July 25, 1939, five weeks before the outbreak of World War II, the Polish General Staff's Cipher Bureau disclosed to their French
and British
allies, at Warsaw
, their cryptologic achievements in breaking Enigma ciphers. Part of the disclosures involved Zygalski's "perforated-sheet" method.
The British, at Bletchley Park
, near London
, England
, undertook the production of two complete sets of perforated sheets. The work was done, with the aid of perforators, by a section headed by John R.F. Jeffreys. The sheets were known at Bletchley as Netz (from Netzverfahren, "net method"), though they were later remembered by Gordon Welchman
as "Jeffreys sheets"; the latter term, however, referred to another catalog produced by Jeffreys' section.
The first set was completed in late December 1939. On December 28, part of the second set was delivered to the Polish cryptologists, who had by then escaped from German-overrun Poland to PC Bruno
outside Paris, France. The remaining sheets were completed on January 7, 1940, and were couriered by Alan Turing
to France shortly thereafter. "With their help," writes Rejewski
, "we continued solving Enigma daily keys." The sheets were used by the Poles to make the first wartime decryption of an Enigma message, on January 17, 1940.
In May 1940, the Germans once again completely changed the procedure for enciphering message keys (with the exception of a Norwegian network). As a result, Zygalski's sheets were of no use.
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
Cipher Bureau
Biuro Szyfrów
The Biuro Szyfrów was the interwar Polish General Staff's agency charged with both cryptography and cryptology ....
before and during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, and during the war also by British cryptologists at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
, to decrypt messages enciphered
Cipher
In cryptography, a cipher is an algorithm for performing encryption or decryption — a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts...
on German Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
s.
The Zygalski-sheet apparatus takes its name from Polish Cipher Bureau mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
–cryptologist Henryk Zygalski
Henryk Zygalski
Henryk Zygalski was a Polish mathematician and cryptologist who worked at breaking German Enigma ciphers before and during World War II.-Life:...
, who invented it about October 1938.
Method
Zygalski's device comprised a set of 26 perforated sheets for each of the, initially, six possible sequences for inserting the three rotors into the Enigma machineEnigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
's scrambler. Each sheet related to the starting position of the left (slowest-moving) rotor.
The 26 × 26 matrix represented the 676 possible starting positions of the middle and left rotors and was duplicated horizontally and vertically: a–z, a–y. The sheets were punched with holes in the positions that would allow a "female" to occur.
Polish mathematician–cryptologist Marian Rejewski
Marian Rejewski
Marian Adam Rejewski was a Polish mathematician and cryptologist who in 1932 solved the plugboard-equipped Enigma machine, the main cipher device used by Germany...
writes about how the perforated-sheets device was operated:
Like Rejewski
Marian Rejewski
Marian Adam Rejewski was a Polish mathematician and cryptologist who in 1932 solved the plugboard-equipped Enigma machine, the main cipher device used by Germany...
's "card-catalog
Card catalog (cryptology)
The card catalog, or "catalog of characteristics," in cryptography, was a system designed by Polish Cipher Bureau mathematician-cryptologist Marian Rejewski, and first completed about 1935 or 1936, to facilitate decrypting German Enigma ciphers.-History:...
" method, developed using his "cyclometer
Cyclometer
The cyclometer was a cryptologic device designed, "probably in 1934 or 1935," by Marian Rejewski of the Polish Cipher Bureau's German section to facilitate decryption of German Enigma ciphertext.-History:...
," the Zygalski-sheet procedure was independent of the number of plugboard
Plugboard
A plugboard, or control panel , is an array of jacks, or hubs, into which patch cords can be inserted to complete an electrical circuit. Control panels were used to direct the operation of some unit record equipment...
plug connections in the Enigma machine.
Manufacture
Razor blade
Razor blade may refer to* A razor* The Razor Blade, a 1920s racing car* Razor blade steel, a type of steel originally designed specifically for razor blades...
s, was very time-consuming. By December 15, 1938, only 1/3 of the job had been finished.
On that date, the Germans introduced rotors IV and V, thus increasing the labor of making the sheets tenfold, since ten times as many sheets were now needed (for the now 60 possible combinations of sequences, in an Enigma machine, of 3 rotors selected from among the now 5).
On July 25, 1939, five weeks before the outbreak of World War II, the Polish General Staff's Cipher Bureau disclosed to their French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and British
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
allies, at Warsaw
Warsaw
Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...
, their cryptologic achievements in breaking Enigma ciphers. Part of the disclosures involved Zygalski's "perforated-sheet" method.
The British, at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
, near London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, undertook the production of two complete sets of perforated sheets. The work was done, with the aid of perforators, by a section headed by John R.F. Jeffreys. The sheets were known at Bletchley as Netz (from Netzverfahren, "net method"), though they were later remembered by Gordon Welchman
Gordon Welchman
Gordon Welchman was a British-American mathematician, university professor, World War II codebreaker at Bletchley Park, and author.-Education and early career:...
as "Jeffreys sheets"; the latter term, however, referred to another catalog produced by Jeffreys' section.
The first set was completed in late December 1939. On December 28, part of the second set was delivered to the Polish cryptologists, who had by then escaped from German-overrun Poland to PC Bruno
PC Bruno
PC Bruno was a Polish-French intelligence station that operated outside Paris during World War II, from October 1939 until June 9, 1940. It decrypted German ciphers, most notably messages enciphered on the Enigma machine.-History:...
outside Paris, France. The remaining sheets were completed on January 7, 1940, and were couriered by Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
to France shortly thereafter. "With their help," writes Rejewski
Marian Rejewski
Marian Adam Rejewski was a Polish mathematician and cryptologist who in 1932 solved the plugboard-equipped Enigma machine, the main cipher device used by Germany...
, "we continued solving Enigma daily keys." The sheets were used by the Poles to make the first wartime decryption of an Enigma message, on January 17, 1940.
In May 1940, the Germans once again completely changed the procedure for enciphering message keys (with the exception of a Norwegian network). As a result, Zygalski's sheets were of no use.
See also
- Cryptanalysis of the EnigmaCryptanalysis of the EnigmaCryptanalysis of the Enigma enabled the western Allies in World War II to read substantial amounts of secret Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio...
. - Bomba ("cryptologic bomb")Bomba (cryptography)The bomba, or bomba kryptologiczna was a special-purpose machine designed about October 1938 by Polish Cipher Bureau cryptologist Marian Rejewski to break German Enigma-machine ciphers....
: machine designed about October 1938 by Marian RejewskiMarian RejewskiMarian Adam Rejewski was a Polish mathematician and cryptologist who in 1932 solved the plugboard-equipped Enigma machine, the main cipher device used by Germany...
to facilitate the retrieval of Enigma keys. - BombeBombeThe bombe was an electromechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted signals during World War II...
: a machine, inspired by Rejewski's "cryptologic bomb," that was used by British and American cryptologists during World War II. - Punched cardPunched cardA punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...
. - Jacquard loomJacquard loomThe Jacquard loom is a mechanical loom, invented by Joseph Marie Jacquard in 1801, that simplifies the process of manufacturing textiles with complex patterns such as brocade, damask and matelasse. The loom is controlled by punched cards with punched holes, each row of which corresponds to one row...
.
External links
- Javascript demonstration of Zygalski sheets
- "Polish Enigma Double"
- About the Enigma (National Security Agency)
- http://www.armyradio.com/publish/Articles/The_Enigma_Code_Breach/The_Enigma_Code_Breach.htm"The Enigma Code Breach" by Jan BuryJan BuryJan Bury is a Polish politician. He was elected to Sejm on September 25, 2005 getting 12050 votes in 23 Rzeszów district, candidating from Polish People's Party list....
] - The „Enigma” and the Intelligence
- www.enigmahistory.org
- "Codebreaking and Secret Weapons in World War II" By Bill Momsen
- A Brief History of Computing Technology, 1930 to 1939