Many code-breakers
begin by seeing how often certain letters and words appear in
a message.
In English,
for example, E,
T,
A
and O
are the commonest letters. TH,
HE,
AN
and RE
are common combinations. THE,
OF,
AND
and TO
are common words. You cannot write long messages without repeating
some of these.
The code-breaker
can begin to guess at the meanings by studying these REPETITIONS.
Before computers were used it could take weeks or months of intense
study and mathematical calculation to crack the code.
Sometimes
a code-breaker is helped by the capture of an enemy codebook,
or by mistakes made by the person sending the message.
Once a code
has been broken, other messages sent in that code can easily be
deciphered.
Who
invented codes and ciphers?
