John Herivel

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John William Jamieson Herivel (born August 29, 1918 in Belfast , Northern Ireland , † January 18, 2011 in Oxford , England ) was a British historian and cryptanalyst . During the Second World War he played a major role in the Government Code and Cypher School (GC&CS) in Bletchley Park , England , the military service that successfully deciphered German communications contributed to the breakage of the German rotor key machine Enigma .

His cryptanalytic performance, recognizing negligence on the part of German Enigma operators in dealing with their encryption machines and using them to break radio messages, will not be forgotten. The method he devised was named Herivel Tip (German: Herivel tip ) or Herivelismus in his honor . In addition, Herivel was also active as a historian and writer. He has written books and articles on Isaac Newton , Joseph Fourier and Christiaan Huygens, as well as an autobiographical work on his own work in Bletchley Park entitled "Herivelismus and the German Military Enigma" .

youth

John Herivel was born in the Northern Irish capital Belfast and attended Methodist College Belfast (MCB) as a schoolchild from 1924 to 1936 . In 1937 he received a mathematics scholarship and began studying at the University of Cambridge .

Bletchley Park

From there, the 21-year-old student John Herivel was poached by Gordon Welchman , who placed him in the service of GC&CS in Bletchley Park (BP), 70 km north-west of London . On January 29, 1940 Herivel was assigned to the newly founded Hut 6 (German: Baracke 6), i.e. the organizational unit of BP, which, under the direction of Gordon Welchman and his deputy Conel Hugh O'Donel Alexander , was responsible for the deciphering of the German army and the Luftwaffe should deal with the Enigma I encrypted radio messages. He received an introduction to the functionality of the German encryption machine and the recognized customs within the German radio networks from Alan Turing, among others .

At the beginning of 1940, BP was still far from being able to routinely “ crack ” German radio messages . In particular, there was hardly any machine support for the British “codebreakers” , as it was only later available in the form of the electromechanical “cracking machine”, the so-called “ bomb ” , devised by Alan Turing and further improved by Gordon Welchman . Herivel was given the task of familiarizing himself with the key network operated by the German Air Force, which the British code breakers had given the code name "Red" (German: Rot).

At that time there were no operational "bombs" and the code breakers were forced to use manual methods to break the German radio messages. The procedures were extremely tedious, slow, and error-prone. Herivel was given the task of thinking about improved methods of attack. He followed his inspiration and, instead of concentrating on the cryptanalytic side, he put himself in the role of a German encryptor whose daily task was to set his encryption machine to the current daily key every morning . In addition to the selection of the three rollers ( roller position ) and the prescribed plug arrangement ( plug connections ), this also included the setting of the rings ( ring position ) of the rotating rollers of the machine as a third key .

The operator had to release a small spring lock , then turn the roller and let the locking pin lock into one of the 26 possible positions on the ring of the roller, which was in the (then) secret key board for each day and for each of the three Rolling was prescribed. As a fourth and last partial key, the rollers had to be turned into any starting position (the so-called basic position ), which was then used to encrypt the saying key . The basic position was transmitted as part of the radio message header, so it was clearly visible.

The Herivel tip

The ring position of each roller is indicated by the red arrow visible on the middle roller in the picture, which here points to 01

The operators were instructed to come up with this freely selectable basic position for the spell key encryption so that it should be as unpredictable as possible. Herivel, however, intuitively assumed that not infrequently, due to lack of time or convenience, would not turn the rollers and thus set a basic position that was as random as possible, but instead simply keep the rollers in the position in which they were after setting the rings found. Thus, the ring position would be identical or at least almost identical to the basic position, which was also known to the code breakers as part of the message head.

Herivels tip was now his advice that the (known) basic position roughly corresponds to the (unknown) ring position. This resulted in a considerable simplification of work for the code breakers from Bletchley Park, who no longer had to consider all 26³ = 17,576 ring positions of the Enigma, but only had to investigate around a dozen probable positions.

For a not very long but extremely critical phase, which lasted from May to August 1940 (see also: Battle of Britain ), "Herivelism", as it was also called, was one of the essential methods to ensure the continuity of the Enigma's ability to decipher and thus not lose touch with German radio messages.

Fonts

  • The Background to Newton's Principia . Oxford at the Clarendon Press 1965
  • Joseph Fourier: The Man and the Physicist . Oxford University Press 1975
  • Herivelismus and the German Military Enigma , M. & M.Baldwin, 2008, ISBN 0-947712-46-1 .

literature

Web links

Individual evidence

  1. ^ Obituary in the Guardian . Retrieved February 15, 2011.
  2. ↑ John William Jamieson Herivel (English). Retrieved February 2, 2017.
  3. ^ Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 11. ISBN 0-947712-34-8
  4. ^ Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 200. ISBN 0-947712-34-8
  5. ^ Hugh Sebag-Montefiore: Enigma - The battle for the code . Cassell Military Paperbacks, London 2004, p. 90. ISBN 0-304-36662-5
  6. ↑ Michael Smith: Enigma decrypted - The "Codebreakers" from Bletchley Park . Heyne, 2000, p. 42. ISBN 3-453-17285-X
  7. ^ Hugh Sebag-Montefiore: Enigma - The battle for the code . Cassell Military Paperbacks, London 2004, p. 92. ISBN 0-304-36662-5
personal data
SURNAME Herivel, John
ALTERNATIVE NAMES Herivel, John W.
BRIEF DESCRIPTION British cryptologist
DATE OF BIRTH August 29, 1918
PLACE OF BIRTH Belfast
DATE OF DEATH January 18, 2011
Place of death Oxford