The Turing Bombe Rebuild Project
The bombe was an electro-mechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted secret messages during World War II. The US Navy and US Army later produced their own machines to the same functional specification, but engineered differently from each other and from the British Bombe.
The initial design of the bombe was produced in 1939 at the UK Government Code and Cypher School (GC&CS) at Bletchley Park by Alan Turing, with an important refinement devised in 1940 by Gordon Welchman. The engineering design and construction was the work of Harold Keen of the British Tabulating Machine Company. It was a substantial development from a device that had been designed in 1938 in Poland at the Biuro Szyfrów (Cipher Bureau) by cryptologist Marian Rejewski, and known as the "cryptologic bomb" (Polish: bomba kryptologiczna). The first bombe, code-named Victory, was installed in March 1940 while the second version, Agnus Dei or Agnes, incorporating Welchman's new design, was working by August 1940.
The bombe was designed to discover some of the daily settings of the Enigma machines on the various German military networks: specifically, the set of rotors in use and their positions in the machine; the rotor core start positions for the message—the message key—and one of the wirings of the plugboard.
In 1994 a group led by John Harper of the BCS Computer Conservation Society started a project to build this working replica of a bombe. The project required detailed research, and took 13 years of effort before this replica was completed, which was then put on display at the Bletchley Park museum. In March 2009 it won an Engineering Heritage Award.
Each vertical set of three drums, together with a reflector plugboard on the left hand end of the machine, is the electrical equivalent of a German Enigma machine. This set of three is often refered to as a "Letchworth Enigma".
The drum colours are used to identify the internal wiring where this is the same as an Enigma wheel but provided twice for electrical reasons. There are 36 such Letchworth Enigmas with thier external connection brought out to the rear of the machine.
The top drums go around the fastest but in fact are equivalent to the Enigma's slow, left hand wheel. The top drums of each three wheel set rotate continuously, with the middle ones stepping by ratchet action after the top drums have performed 26 electrical tests. The bottom drum steps again by ratchet action at the same time as the middle ones but only once in every rotation of the middle drums.
On the right and hidden by the demonstrator, are the indicator drums. These are permanently attached to the machine. When the machine 'stops' they indicate a possible conditions that after further processing, might lead to the settings used by the Germans on their Enigma machine to encypher the text.
They would be set to ZZZ before starting a run. If during a run no 'stop' were found the machine would then return to ZZZ and come to a halt having carried out 26x26x26 unsuccessful tests.
The Turing Bombe Rebuild Project
The bombe was an electro-mechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted secret messages during World War II. The US Navy and US Army later produced their own machines to the same functional specification, but engineered differently from each other and from the British Bombe.
The initial design of the bombe was produced in 1939 at the UK Government Code and Cypher School (GC&CS) at Bletchley Park by Alan Turing, with an important refinement devised in 1940 by Gordon Welchman. The engineering design and construction was the work of Harold Keen of the British Tabulating Machine Company. It was a substantial development from a device that had been designed in 1938 in Poland at the Biuro Szyfrów (Cipher Bureau) by cryptologist Marian Rejewski, and known as the "cryptologic bomb" (Polish: bomba kryptologiczna). The first bombe, code-named Victory, was installed in March 1940 while the second version, Agnus Dei or Agnes, incorporating Welchman's new design, was working by August 1940.
The bombe was designed to discover some of the daily settings of the Enigma machines on the various German military networks: specifically, the set of rotors in use and their positions in the machine; the rotor core start positions for the message—the message key—and one of the wirings of the plugboard.
In 1994 a group led by John Harper of the BCS Computer Conservation Society started a project to build this working replica of a bombe. The project required detailed research, and took 13 years of effort before this replica was completed, which was then put on display at the Bletchley Park museum. In March 2009 it won an Engineering Heritage Award.
Each vertical set of three drums, together with a reflector plugboard on the left hand end of the machine, is the electrical equivalent of a German Enigma machine. This set of three is often refered to as a "Letchworth Enigma".
The drum colours are used to identify the internal wiring where this is the same as an Enigma wheel but provided twice for electrical reasons. There are 36 such Letchworth Enigmas with thier external connection brought out to the rear of the machine.
The top drums go around the fastest but in fact are equivalent to the Enigma's slow, left hand wheel. The top drums of each three wheel set rotate continuously, with the middle ones stepping by ratchet action after the top drums have performed 26 electrical tests. The bottom drum steps again by ratchet action at the same time as the middle ones but only once in every rotation of the middle drums.
On the right and hidden by the demonstrator, are the indicator drums. These are permanently attached to the machine. When the machine 'stops' they indicate a possible conditions that after further processing, might lead to the settings used by the Germans on their Enigma machine to encypher the text.
They would be set to ZZZ before starting a run. If during a run no 'stop' were found the machine would then return to ZZZ and come to a halt having carried out 26x26x26 unsuccessful tests.