Mair Thomas : Life at Bletchley Park
lecturers to request their service if war broke out , including Gordon who oversaw Hut Six . New technology was desperately needed to face the encrypted codes of the Enigma machine , and the best minds in the country were recruited to save their nation island . Encrypted message systems had changed rapidly from the Great War ’ s simplified pad and paper system . Winterbotham claims Denniston explained that cryptology messages from World War I used the following method :
Denniston explains to me that there were a number of methods used to encypher messages , mostly based on the use of books of numerals held only by the sender and the recipient , but that machines had also been tried out . The basis of encrypting was that each service up to now had used its own particular codebook in which a multitude of words and phrases likely to be used by that particular service had opposite each phrase or word a numerical group . 4
Of course , no code is infallible , as codebooks could become lost or even stolen , but the safest method used during the Great War was the “ one-time pad method ” described as :
In order to make the messages secret , therefore , additional groups of figures known only to the sender and receiver must be added so as to make the final groups in the signal untranslatable by any third party . The safest way to do this is for both the sender and receiver to have a sort of tear-off pad , on each sheet of which are columns of four digit groups printed absolutely at random …. Once used the whole page of the pad is torn off and destroyed …. And was at the time the only known absolutely safe cypher . 5
A few years following the war , the safest cipher method became outdated , making way for a mechanical and computerized method of cryptology that the Germans created in the 1920s , called the Enigma machine . According to Gordon Welchman , under Hitler ’ s command , the entire German military was overhauled , creating divisions within branches to produce a fastmoving force . To be effective , the German ’ s relied on “ revolutionary radio communication capabilities .” 6 A highly trained German “ mobile signals organization ” was developed and “ equipped with an Enigma cipher machine .” 7 Britain ’ s only hope was to develop an intricate network of Y stations to intercept German radio transmissions to send to GCHQ .
Sinclair McKay ’ s book , The Secret Listeners : How the Y Service Intercepted the Secret German Codes for Bletchley Park , provides insight into the frontlines of codebreaking . 8 The men and women assigned to Y stations spent countless hours listening across the airways for enemy communication . The Y Station workers would record the coded messages . Mair Thomas describes the importance of the Y stations to the work done at BP :
11