Toward the end of World War I, the British began manufacturing thousands of small cipher machines, Pletts Cryptographs, for use by the allied forces. The machine had a mechanism that regularly altered the encoding scheme; so, the first "a" might be changed to an "f" and the next "a" to an "r." No one had been able to break the cipher. Just to be sure, the American military passed it on to a remarkable husband-and-wife team, William and Elizebeth Friedman. Within three hours, they broke the first of five coded messages. "This cipher is absolutely indecipherable," it said.
William Friedman was born in Russia and came to the United States as an infant. Later he studied genetics, and then settled down at the Riverbank Laboratories near Chicago, on the estate of an eccentric millionaire. Elizebeth had majored in English and got involved in solving the controversy according to which Francis Bacon was the real author of Shakespeare plays and sonnets. (Bacon had invented a secret code that replaced the entire alphabet by combinations of two letters, a and b, and had allegedly hidden a secret message in "his" works.)
After they met, the couple became the greatest makers and breakers of secret messages in history. Repeatedly, they accepted challenges to solve unbreakable ciphers--and succeeded. They unraveled secret messages from rumrunners during Prohibition, from narcotics traffickers in the 1930s, and they broke Japan's highest diplomatic cipher just before World War II. They spent the rest of their lives working for the government, doing the kind of work noted in text Application 6.1, at a much more sophisticated level of course.
Perhaps it is no accident that William Friedman started his career as a geneticist, for the most fascinating example of code breaking during the twentieth century involved the work of geneticists who deciphered the genetic code. Indeed, they utilized the very techniques pioneered by the Friedmans. Consider how counter-intelligence agents can trick a spy, who is known to transmit coded messages, by feeding a document to the spy and then reading the coded message based on that document. The long secret messages at the heart of the DNA double helix were deciphered in a similar manner. (The story is summarized in "Breaking the Code," The Economist, November 28, 1992.)
An interesting final note: Since the couple's deaths, the U.S. National Security Agency (NSA), which Lt. Colonel William Friedman founded, created the Data Encryption Standard (DES), designed to help business and government transmit sensitive data via wireless phones and computer lines. DES scrambles computer messages that are already composed of zeros and ones. As the text notes, originally, there were 256 possible keys that could be used (which is a number exceeding 72,000 million million). The latest Rijndael technique even uses a number of combinations equal to 1,100 followed by 75 zeros to scramble and unscramble messages. Allegedly, today's best computers would take 149 trillion years to crack the code. Indeed, despite much effort worldwide, nobody has been able to break such a code. But that may not last.
Since the mid-1990s, scientists have been developing a DNA computing system that substitutes strings of As, Ts, Cs, and Gs (the four chemical units of DNA) for the 0s and 1s of the silicon-chip computer. The biological computer, furthermore, processes information by synthesizing DNA molecules in a test tube rather then by manipulating the flow of electrons through logical circuits. Theoretically, trillions of DNA molecules undergoing chemical reactions could break the DES code in four months!