Hut 6 - The start of cribbing for the bombes (August 1940- May 1941)

Introduction

From August 1940, hut 6 received its first Bombe. The use of manual methods persists firstly because there are few bombes and also because they allow breaking new keys (Enigma network) for which a priori we have no crib.

Cryptologists at Hut 6 are discovering the art of cribbing (finding cribs) which is the essence of using bombes.

This is also the beginning of the use of key rules which (in addition to cillies), drastically decrease the time of using bombes. At the time, bombes were a scarce commodity.

The war

After the surrender of France, Germany planned to invade England. As a prerequisite, it wants to annihilate the RAF: it is the Battle of Britain, which is essentially an air battle. After its failure (in October 1940), Germany wanted to destroy the morale of the English and lead them to accept a peace treaty: it was the Blitz (the bombing of London). The opposite is true: the British want to continue the war until Nazi Germany is annihilated. The Germans stopped the Blitz in May 1941.

From December 1940, the British tried to thwart the expansionist views of Italy in North Africa. The English come to their end and stop the Italian advances. It was then that the German forces (Afrika Korps), commanded by Romel, came to the aid of the Italians in March 1941. In less than a month, the Afrika Korps reached Tobruk.

The keys

The Red key remains the main key attacked by Hut 6. As the warlike events unfold, several keys appear (we continue to use colors):

Brown (1er break: 2 sept 40): associated with German bombers
Orange (1st break: 10 Dec 40): SS (Schutzstaffel)
Violet (1st break; 24 dec 40)
Light Blue (1st break: 28 Feb 41): (mediterranan operational key [Air Force])
Chaffinch [Called AF5 at the start] (1st break: March 26, 41): Rommel's Africa Korps
Onion (1st break: 8 May 41)

The Pink network is detected from Feb 41, but not broken (it will be from April 1942).

Organization and working

We find the previous services:

RR: the recording room for messages from Y stations.
DR: The cryptogram decryption chamber for networks whose keys have been found.

But the MR (machine room), although it continues to deal with manual methods (Cillies, ...), also prepares the menus for the bombes and tests the stops that occur and finishes finding the other elements of the key (all steckers, the ringstellung). It is the one who dialogues with Hut 1, which houses the bombes, which are managed by mainly female personnel. In addition, it follows the evolution of key rules.

To relieve MR, the Testing Room is created to test stops. It was also called Netz Room.

The big news is the appearance of the CR (Crib Room) from October 1st. It is strategically responsible for finding the cribs which will be the basis of the bombe menus. At first, it was made up of four people under the aegis of Stuart Milner-Barry who had studied the Crib problem as soon as the bombe were under construction. (cribery problem).

The Research section (which in a way has always existed) deals with keys that have not yet been broken.

When a key is broken, the decrypted messages are sent to Hut 3 and then when they come back they are examined for new cribs. Subsequently, the decrypted messages will be examined by a member of the Crib room before being forwarded to Hut 3.

Re-encryption is rare but very useful, for example between Red and Brown or between Red and Light Blue.

Staff

It was not until the summer of 1940 that the Hut 6 would operate 24 hours a day with three teams with three or four people per team (Greenberg 2014).

As we can see, at this time, the number of cryptalysts in Hut 6 is less than twenty people.

Equipment (Bombes)

The first Spider-type bombe (equipped with the diagonal board : The Turing / Welchman bombe) arrived in BP in August 1940. It was called Agnus.

The first Victory bombe returned to the factory to receive a diagonal board and therefore returned in BP in October 1940.

In June 1941, BP still had only 4 bombes.