A tough challenge.

The number of different grids possible was, in principle, enormous. For each row there were 25x24x...x16 = 12 thousand billion different ways of arranging the white and black squares. Taking into account that there were 24 rows, the number of different grids increases to the astronomical figure of 7 followed by 36 zeros, a considerably greater number of possibilities than generated by an Enigma machine. It was consequently completely out of the question for a cryptanalyst to try every possibility!

The Swedish mathematician Arne Beurling (who has been ranked alongside Rejewski and Turing both as a mathematician and a cryptanalyst) gave his conclusion on RS44 after the war: “The possibilities for successful cryptanalysis are nil, even under the best of circumstances”. Maj. Hugh Skillen, an officer in the British Y Service, wrote that ‘it defeated our cryptographers’. Sir Harry Hinsley, referring to a ‘new’ medium-grade cipher by which he undoubtedly meant RS44, said that it was practically unbreakable.

Bletchley Park tried hard to find a solving technique, with over 100 people employed on the task, but after a few months gave up. An exception was made for Police messages that gave a unique picture of the last days of the Nazi regime and of its individual leaders. Although the intelligence gained suffered from long delays and had a disproportionately high cost, it nevertheless provided posterity with a unique picture and for this reason wartime messages continued to be decrypted after VE-day.