Intercepts and code breaking
Ciphers help protect secret messages, but they do not destroy the meaning completely. Like a word puzzle, the sense of the message remains locked inside. An enemy who intercepts the signal will try hard to find the key. Intelligence agencies employ code-breakers called cryptanalysts to do this. With a substitution cipher , a cryptanalyst starts by counting letters. In English, "E" is used more often than other letters. So, if in the message "W" appears most, it probably stands for "E.’ The next step is to look for two-letter words ending in "E.” There are only four in English: he, me, be, and we. Then the cryptanalyst will look for letters that stand on their own—in English there are just two one-letter words, "A"and "I". With techniques like these and even more complex ones, cryptanalysts can solve elaborate , cipher puzzles, although it can sometimes take them a long time. Computers speed the process, but, cryptanalysts need to be ver