Bletchley Park — Hugh Davies 13th October 2014.

Hugh said that the digital age star­ted at Bletchley Park.

Many of the machines were oper­ated by WRENS where the work force was three women to one man.  Sixty per cent were uni­formed per­son­nel and forty per cent were civil­ians.  Rank/status within the uni­formed ranks didn’t matter, so if any army private was intel­li­gent and cap­able enough, he could be pro­moted to major within a week.

Hugh men­tioned that the com­puters were needed to find out what the cap­ab­il­it­ies of the enemy were and what their inten­tions were.

Messages were sent in code and the inter­pret­a­tion of mes­sages and break­ing the code was para­mount. The human factor came into play as, having inter­cep­ted the mes­sage, they then had to decide what to do with it and to whom they would send it, so a lot depended on human judg­ment and decisions.  He stressed that once any mes­sage was “in the air­waves” there was no pri­vacy as it could, if the person had the right resources,  be retrieved but still needed to be decoded.  Basically the sender used a machine to trans­mit the mes­sage in code to the recip­i­ent who had a sim­ilar machine pro­grammed with the same code, thus cut­ting out a pos­sible inter­ceptor.

Messages could be in codes which had hidden mean­ings e.g. “it is rain­ing in Liverpool today” or in an extinct lan­guage e.g. Navaho.  The book Rebecca was used when state­ments such as 10 to 5 meant page 10 word 5 etc.  The Germans were aler­ted to this fact and bought the com­plete stock of Rebecca  novels in Spain.

Ciphers… these were sub­sti­tut­ing one letter for another. A poly­al­pha­betic cipher alters a letter every time it is used.

Messages were inter­cep­ted by listen­ing out sta­tions and sent to Bletchley Park. Once decoded they were dis­trib­uted to gov­ern­ment offices i.e. the Air Ministry. Distribution was equally as import­ant as the col­lec­tion of mes­sages because only the very top people were informed.

The Germans were con­vinced that their codes were unbreak­able as if a com­puter is always random as its code could not be broken.  The ele­ment of non-randomness enables the code to be cracked by using greet­ings like “Happy Christmas” etc. and by using the same “sign off” words enabled the codes to be broken.

No one at Bletchley Park even talked about their work for over thirty years.  A hus­band and wife, mar­ried for many years, never knew that they had both worked at Bletchley Park.

So much interest was gen­er­ated by the talk that that a  future visit to Bletchley Park by the club was pro­posed.