The Hut 6 story

Periods:

Introduction

At the start of World War II, the English code breaking organization, CG&CS, moved from London (on Broadway) to the manor house of Bletchley Park (BP). The main branch of the CG&CS was called Hut 6. It was responsible for deciphering the Enigma messages of the German Air Force and the German Army. Hut 6 corresponds to the name of the wooden hut that housed this organization. So we can see that Hut 6 is both the name of a building and even more the name of an organization.

Before Hut 6

But before the birth of Hut 6, English cryptologists were already familiar with the Enigma. Between 1927 and 1938 they had mastered the Commercial Enigma. Then, thanks to the information provided by the French in September 1938, they acquired a good theoretical knowledge of the military Enigma (Enigma I) without being able to find the wiring of the rotors.

In July 1939, the Poles revealed to the French and English their mastery of Enigma. They give each of them a replica of the Enigma. They trust the British to make the Zyglaski sheets, which (if the Germans did not change their procedures) would make it possible to decipher the daily keys. Two sets are planned: one for the English and the other for the Franco-Polish team (the Poles having joined the French after the annihilation of Poland).

The Polish methods were not limited to Zygalski leaves, they also used a machine, called "Bombe" which automatically found part of the key. Turing, taking inspiration from it, creates a similar machine but based on the use of cribs (a plain text supposed). Welchman upgrades the Turing Bombe and makes it very powerful operationally.

Birth of Hut 6 (Nov 1939 - May 1940)

From November 1939, during the production of the Zyglaski sheets, Gordon Welchman created on Paper Hut 6, that is to say the operational organization which must decipher the Enigma messages of the army and the air force. His proposal is accepted. From January 1940, Hut 6 takes shape and decryption begins.

The great crisis (May 1940- August 1940)

At the beginning of May 1940, the Germans changed their procedures and Zygalski's sheets were no longer usable. For 20 days, it's a complete blackout. Then the decipherments are resumed using manual methods: the cillies and the Hérivel tip.

The start of cribbing for the bombes (August 1940- May 1941)

From August 1940, Hut 6 received its first Bombe. The use of manual methods continues and in particular makes it possible to break new keys (Enigma network). Cryptologists at Hut 6 are discovering the art of cribbing (finding cribs) which is the essence of using bombes.

Beginning of the use of key rules which drastically decrease the number of bombe runs.

Expansion and consolidation (June 1941 - January 1943)

The number of keys to manage increases significantly. Fortunately the personnel of Hut 6 and the number of bombes increases accordingly. Hut 6 is getting more complex. The research section is structured. Appearance of the school to train new staff.

The expansion of hut6 was accelerated by a request addressed directly to Churchill by the directors and deputy directors of hut6 and hut8.

The bombes are still few and are shared with the hut 8 responsible for breaking the keys of the navy.

Reorganization: the Watch becomes the center of the hut (February 1943-September 1944)

The search services for cribs and their use via menus merge to form the "Watch". Each members of the Watch manages one or more keys.

The members of Hut 6 are grouped together in a single building: Block D.

The Enima evolves (appearance of the reflector D) as well as the procedures, which complicates the work of the staff of Hut 6.

Air force-army separation (October 1944-May 1945)

The last major change within Hut 6: the separation of key management for the Army and Air Force.