Cryptanalyst

The art of the cryptanalyst lies in deciphering the plain text from the ciphertext without prior knowledge of the secret key required for decryption

As a cryptanalyst (also: cryptanalysts or cryptanalyst ; English cryptanalyst ), code breaker (also: Kodeknacker , Kodebrecher or code breaker ; English Codebreaker ) or Entzifferer referred to a person who is (as a branch of cryptology ) with the deciphering of secret texts concerned, ie texts by encrypting a plaintext using a key generated.

The great challenge and art of the code breaker is to extract its information from the ciphertext without prior knowledge of the secret key required for decryption . He uses methods of cryptanalysis , i.e. deciphering procedures. This includes statistical evaluations of the ciphertext, such as counting the frequency of letters , searching for patterns , searching for periods or determining the coincidence index .

The activity of the cryptanalyst is described as deciphering , uncovering , solving , reading along , breaking or colloquially as cracking (the ciphertext or the procedure) (see also: Terminology ).

Code breakers in history

Francis Walsingham founded the British secret service and protected his queen against assassinations with the help of code breakers (oil painting around 1587)

Edgar Allan Poe was a writer and a passionate code breaker ( daguerreotype 1848)

While the profession of cryptanalyst today is more oriented towards information theory and is mostly practiced by mathematicians and computer scientists , in earlier centuries it was often trained linguists who were able to break into foreign ciphers with linguistic methods and with great linguistic empathy and intuition . In the simplest case, the encryption was broken by guessing the secret code word , which the encryptor had often chosen too carelessly. In principio erat verbum (German: “In the beginning was the word”) or Omnia vincit amor (German: “Love always wins”) are classic examples of comparatively long key words that could be guessed very quickly by an experienced code breaker.

Broken encryption could have significant political implications. An example from history is the Babington plot , in which British Catholics planned a conspiracy to assassinate the Protestant English Queen Elizabeth I and replace her with the Queen of Scotland , Catholic Mary Stuart . By intercepting the conspirators' encrypted communications, which was deciphered by the very experienced and yet almost completely unknown code breaker Thomas Phelippes , the English around Francis Walsingham were able to uncover the plot and unmask the conspirators. This eventually led to the execution of Mary Queen of Scots.

Another cryptanalyst who has not been forgotten thanks to his literary merits is the American writer Edgar Allan Poe . Famous his short story The Gold Bug (German: The Gold Bug ), in which the narrator Legrand succeed as a code breaker to decipher a mysterious character code as a guide to a hidden treasure of the pirate Captain Kidd turns. Poe himself was a passionate code breaker who deciphered encrypted love messages from the British daily newspaper The Times for pleasure and also urged his own readers to send him encrypted messages, which he cracked with skill and experience and to the astonishment of his followers seemingly effortless.

At the beginning of the twentieth century did a French cryptanalyst, by the German military in World War I by means of wireless telegraphy to sent secret messages break . On the German Western Front, from March 1, 1918, ADFGX encryption was used to keep radio messages secret. The French artillery officer Georges Jean Painvin managed to decipher it. In doing so, he made a significant contribution to the fact that German soldiers did not succeed in taking Paris in the First World War. He saw this himself as his greatest life achievement.

The most important and famous code breakers in human history are undoubtedly the code breakers from Bletchley Park , who, building on Polish preparatory work , succeeded in doing this thanks to their intellectual capabilities and the use of special cryptanalytic machines ( Turing bomb and Colossus ) and a high level of personnel deciphering German communications during the Second World War and thus contributing significantly to the decision of the war . On the site of Bletchley Park there is an honor roll (Roll of Honor) for deserving Codebreaker .

Famous cryptanalysts

• al-Kindī (around 800–873) - described the frequency analysis as a method for breaking monoalphabetic substitutions
• William Friedman (1891–1969) - father of American cryptology
• Friedrich Wilhelm Kasiski (1805–1881) - broke the Vigenère cipher
• Dillwyn Knox (1884–1943) - was one of the first British to crack the German ENIGMA
• Georges Painvin (1886–1980) - broke the German ADFGX process during the First World War
• Agnes Meyer Driscoll (1889–1971) - broke numerous Japanese proceedings since the 1920s
• Marian Rejewski (1905–1980) - laid the foundations for breaking ENIGMA as early as 1932
• Claude Shannon (1916–2001) - formulated the maxim "The enemy knows the system used"
• Alan Turing (1912–1954) - developed the cryptanalytic "cracking machine" named after him against ENIGMA
• Bill Tutte (1917–2002) - clarified the German key addition ( Lorenz SZ 40 )
• Gordon Welchman (1906–1985) - improved the Turing bomb by developing the diagonal board

See also

• ADFGX
• Brute force method
• Chi test
• Crib
• Codebook
• Differential cryptanalysis
• Friedman test (cryptology)
• Frequency analysis
• Kasiski test
• Coincidence index
• Collision attack
• Linear cryptanalysis
• Pattern search (cryptology)
• Dictionary attack

literature

• Friedrich L. Bauer : Deciphered Secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin et al. 2000, ISBN 3-540-67931-6 .
• Francis Harry Hinsley , Alan Stripp (Eds.): Codebreakers. The inside story of Bletchley Park. Oxford University Press, Oxford et al. 1993, ISBN 0-19-820327-6 .
• David Kahn : The Codebreakers. The Story of Secret Writing. 9th printing. Macmillan, New York NY 1979, ISBN 0-0256-0460-0 .
• Rudolf Kippenhahn : Encrypted messages. Secret writing , Enigma and chip card (= Rororo 60807 non-fiction book. Rororo science ). Rowohlt-Taschenbuch-Verlag, Reinbek near Hamburg 1999, ISBN 3-499-60807-3 .
• Simon Singh : Secret Messages . The art of encryption from antiquity to the times of the Internet (= dtv 33071). Deutscher Taschenbuch-Verlag, Munich 2001, ISBN 3-423-33071-6 .
• Simon Singh: Codes. The art of encryption. History, secrets, tricks (= dtv 62167 series Hanser ). Deutscher Taschenbuch-Verlag, Munich 2004, ISBN 3-423-62167-2 .

Web links

• Notable people in cryptology
• The Bletchley Park Roll of Honor (English)

Individual evidence

1. ↑ The Bletchley Park Roll of Honor , accessed June 13, 2019.