The Breaking of German Naval Enigma
by Tony Sale | Back to Naval Enigma Index |

Tony Sale's
Codes and Ciphers

Turing's Work.

1) The breaking of the indicator system

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 indicator system.

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 1939.

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.

This page was originally created by the late Tony Sale
the original curator of the Bletchley Park Museum