Computer Security and Cryptography

6.9 CRYPTANALYSIS OF THE ENIGMA

Cryptanalysis of the Enigma machines first began in Poland at the Polish Cipher Bureau in 1932. When the United Kingdom declared war on Germany after its invasion of Poland on September 1, 1939, a group, including Alan Turing, was assembled to attempt cryptanalysis of the German Enigma traffic at Bletchley Park, a town about 100 kilometers from London, where the Government Code and Cypher School had just been relocated.

The first attacks on Enigma traffic came from a group of Polish mathematicians including Marian Rejewski [Rejewski, 1981] and his colleagues Jerzy Rozycki and Henryzk Zygalski. They examined a commercial Enigma machine and studied the properties of the Enigma encipherment equation.

Bombe is French for bomb; the same word describes a class of pastries normally hemispherical in shape. The actress Jacqueline Bisset creates an ice cream bombe in the movie Who Is Killing The Great Chefs of Europe. A picture of a christmas bombe may be found in the cookbook Chocolat: Extraordinary Chocolate Desserts by Alice Medrich.

The bombe was also a programmable processor constructed by Rejewski and his colleagues. Its function was to use the structure imposed by cribs to test and eliminate certain plugboard and rotor setting combinations.

Why the name bombe? Members of the Polish Cipher Bureau proposed the architecture for a “computer” to aid in the decipherment of the Enigma ciphertext. It is reported that their inspiration came in a restaurant at ...