Alan Turing started where the Poles left off, with the 100 or so messages from May
1st-8th 1937 whose starting positions were known.
From these he had the two four letter groups, the indicators, from each
message and also the message setting, ie the start position for deciphering the
message which the Poles had found.
Using these and some very elegant deductions, Turing worked out the complete
At the same time, as he later said, "I thought of the method of Banbarismus,
but was not sure that it would work in practice". This was at the end of
2) In early 1940, joined by Peter Twinn, he started an attack on messages for
28th November 1938 using Forty Weepy Weepy cribs. The reason for going back so
far was that only 6 steckers were being used at that time and the
FortyWeepyWeepy cribs were working. These messages were broken after a
fortnight's work and four other days also came out.
These breaks were helped by the first use of the EINS catalogue.
The EINS catalogue.
Once messages began to be deciphered, it was realised that the German word
EINS was by far the most frequent word in Naval messages.
It was then decided to take on the prodigious task of cataloguing the
encipherement of EINS at all 105,000 possible start positions. (on the three
wheel Enigma). This was done BY HAND.
Later it was put onto punched cards for Freeborne's section to use.
To use the EINS catalogue consecutive groups of four letters in the message
were looked up to see whether they were an encipherement of EINS.
Then with an Enigma machine set to these settings the following characters
were deciphered to see if German came out.