William Friedman is most famous for breaking Purple, the cipher used by the Japanese in World War Two (hence the name of the book). However, he also played a critical role in saving countless Allied lives in World War One. The British army had decided to use a field code for their army that they thought was unbreakable. Just to make sure, they sent several messages enciphered in the code to Mr. Friedman, who promptly found a major vulnerability in the code’s structure and notified the British just before they put the code into regular use. Stopping the use of the flawed code was undoubtedly a lifesaver for the Allied forces. The excellent book The Man Who Broke Purple discusses this incident and many more in the incredible life of William Friedman. I would highly recommend it.
By Brandon J.