The word ‘hacker’ conjures up an image: an evil person keen on disrupting systems for fun’s sake-and so that he (a hacker is usually a ‘he’) can boast to his friends about the systems he’s breached.

One of the Second World War’s most fascinating stories is that of the Allied codebreakers, who deciphered a vast number of German secret messages by decrypting their ingenious ciphering machine, the ...