A cipher is constantly under attack from codebreakers. When the codebreakers have developed a new weapon that reveals a cipher's weakness, then the cipher is no longer useful. It either becomes extinct or it evolves into a new, stronger cipher. In turn, this new cipher thrives only until the codebreakers identify its weakness, and so on. This is analogous to the situation facing, for example, a strain of infectious bacteria. The bacteria live, thrive and survive, until doctors discover an antibiotic that exposes a weakness in the bacteria and kills them. The bacteria are forced to evolve and outwit the antibiotic, and, if successful, they will thrive once again and re-establish themselves. The bacteria are continually forced to evolve in order to survive the onslaught of new antibiotics. (查看原文)
Winston Churchill was full aware of the importance of the Bletchley decipherments, and on September 6, 1941, he visited the codebreakers. On meeting some of the cryptanalysts, he was surprised by the bizarre mixture of people who were providing him with such valuable information...Churchill muttered to Sir Stewart Menzies, head of the Secret Intelligence Service, "I told you to leave no stone unturned, but I didn't expect you to take me so literally." (查看原文)
