William F . Friedman William Frederick Friedman ( September 24 , 1891 – November 12 , 1969 ) was a US Army cryptographer who ran the research division of the Army ' s Signals Intelligence Service ( SIS ) in the 1930s , and parts of its follow - on services into the 1950s . In 1940 , subordinates of his led by Frank Rowlett broke Japan ' s PURPLE cipher , thus disclosing Japanese diplomatic secrets before America ' s entrance into World War II . Early life . Friedman was born Wolf Friedman ( , ) , in Kishinev , Bessarabia , the son of Frederick Friedman , a Jew from Bucharest who worked as a translator and linguist for the Russian Postal Service , and the daughter of a well - to - do wine merchant . Friedman ' s family fled Russia in 1892 to escape the virulent anti - Semitism there , ending up in Pittsburgh , Pennsylvania . Three years later , his first name was changed to William . As a child , Friedman was introduced to cryptography in the short story " The Gold - Bug " by Edgar Allan Poe . He studied at the Michigan Agricultural College ( known today as Michigan State University ) in East Lansing and received a scholarship to work on genetics at Cornell University . Meanwhile George Fabyan , who ran a private research laboratory to study any personally interesting project , decided to set up his own genetics project and was referred to Friedman . Friedman joined Fabyan ' s Riverbank Laboratories outside Chicago in September 1915 . As head of the Department of Genetics , one of the projects he ran studied the effects of moonlight on crop growth , and so he experimented with the planting of wheat during various phases of the moon . Initial work in cryptology . Another of Fabyan ' s pet projects was research into secret messages which Sir Francis Bacon had allegedly hidden in various texts during the reigns of Elizabeth I and James I . The research was carried out by Elizabeth Wells Gallup . She believed that she had discovered many such messages in the works of William Shakespeare , and convinced herself that Bacon had written many , if not all , of Shakespeare ' s works . Friedman had become something of an expert photographer while working on his other projects , and was asked to travel to England on several occasions to help Gallup photograph historical manuscripts during her research . He became fascinated with the work as he courted Elizebeth Smith , Mrs . Gallup ' s assistant and an accomplished cryptographer . They married , and he soon became director of Riverbank ' s Department of Codes and Ciphers as well as its Department of Genetics . During this time , Friedman wrote a series of 23 papers on cryptography , collectively known as the " Riverbank publications " , including the first description of the index of coincidence , an important mathematical tool in cryptanalysis . With the entry of the United States into World War I , Fabyan offered the services of his Department of Codes and Ciphers to the government . No Federal department existed for this kind of work ( although both the Army and Navy had had embryonic departments at various times ) , and soon Riverbank became the unofficial cryptographic center for the US Government . During this period , the Friedmans broke a code used by German - funded Indian radicals in the US who planned to ship arms to India to gain independence from Britain . Analysing the format of the messages , Riverbank realized that the code was based on a dictionary of some sort , a cryptographic technique common at the time . The Friedmans soon managed to decrypt most of the messages , but only long after the case had come to trial did the book itself come to light : a German - English dictionary published in 1880 . Signals Intelligence Service . The United States government decided to set up its own cryptological service , and sent Army officers to Riverbank to train under Friedman . To support the program , Friedman wrote a series of technical monographs , completing seven by early 1918 . He then enlisted in the Army and went to France to serve as the personal cryptographer for General John J . Pershing . He returned to the US in 1920 and published an eighth monograph , " The Index of Coincidence and its Applications in Cryptography " , considered by some to be the most important publication in modern cryptography to that time . His texts for Army cryptographic training were well thought of and remained classified for several decades . In 1921 he became chief cryptanalyst for the War Department and later led the Signals Intelligence Service ( SIS ) — a position he kept for a quarter century . In 1929 , after The American Black Chamber in New York City was disbanded , its files were entrusted to SIS , and the cryptographic and intelligence services was reorganized to suit its new position at the War Department . Friedman coined several terms , including " cryptanalysis " , and wrote many monographs on cryptography . One of these ( written mostly in his spare time ) was the first draft of his " Elements of cryptanalysis " , which later was expanded to four volumes and became the U . S . Army ' s cryptographic main textbook and reference . Realizing that mathematical and language skills were essential to SIS ' work , Friedman managed to get authority to hire three men with both mathematical training and language knowledge . They were Solomon Kullback , Frank Rowlett and Abraham Sinkov , each of whom went on to distinguished service for decades . In addition he also was finally able to hire a man fluent in Japanese , John Hurt . During this period Elizebeth Friedman continued her own work in cryptology , and became famous in a number of trials involving rum - runners and the Coast Guard and FBI during Prohibition . Solution of cipher machines . During the 1920s , several new cipher machines were developed generally based on using typewriter mechanics and basic electrical circuitry . An early example was the Hebern Rotor Machine , designed in the US in 1915 by Edward Hebern . This system offered such security and simplicity of use that Hebern heavily promoted it to investors . Friedman realized that the new rotor machines would be important , and devoted some time to analysing Hebern ' s design . Over a period of years , he developed principles of analysis and discovered several problems common to most rotor - machine designs . Examples of some dangerous features included having rotors step one position with each keypress , and putting the fastest rotor ( the one that turns with every keypress ) at either end of the rotor series . In this case , by collecting enough ciphertext and applying a standard statistical method known as the kappa test , he showed that he could , albeit with great difficulty , crack any cipher generated by such a machine . Friedman used his understanding of rotor machines to develop several that were immune to his own attacks . The best of the lot , the SIGABA — which was destined to become the US ' s highest - security cipher machine in World War II — was co - invented by Frank Rowlett . At least one patent related to it was finally granted after Friedman had died . In 1939 , the Japanese introduced a new cipher machine for their most sensitive diplomatic traffic , replacing an earlier system that SIS referred to as " RED . " The new cipher , which SIS called " PURPLE " , was different and much more difficult . The Navy ' s cryptological unit ( OP - 20 - G ) and the SIS thought it might be related to earlier Japanese cipher machines , and agreed that SIS would handle the attack on the system . After several months trying to discover underlying patterns in PURPLE ciphertexts , an SIS team led by Friedman and Rowlett , in an extraordinary achievement , figured it out . PURPLE , unlike the German Enigma or the Hebern design , did not use rotor s but stepper switches like those in automated telephone exchange s . Leo Rosen of SIS built a machine — as was later discovered , using the identical model of switch that the Japanese designer had chosen . Thus , by the end of 1940 , SIS had constructed an exact analog of the PURPLE machine without ever having seen one . With the duplicate machines and an understanding of PURPLE , SIS could decrypt increasing amounts of Japanese traffic . One such intercept was the message to the Japanese Embassy in Washington , D . C . , ordering an end ( on December 7 , 1941 ) to negotiations with the US . The message gave a clear indication of impending war , and was to have been delivered to the US State Department only hours prior to the attack on Pearl Harbor . The controversy over whether the US had foreknowledge of the Pearl Harbor attack has roiled well into the 21st century . In 1941 , Friedman was hospitalized with a " nervous breakdown " , widely attributed to the mental strain of his work on PURPLE . While he remained in hospital , a four - man team — Abraham Sinkov and Leo Rosen from SIS , and Lt . Prescott Currier and Lt . Robert Weeks from the U . S . Navy ' s OP - 20 - G — visited the British establishment at the " Government Code and Cypher School " at Bletchley Park . They gave the British a PURPLE machine , in exchange for details on the design of the Enigma machine and on how the British decrypted the Enigma cipher . However Friedman visited Bletchley Park in April 1943 and played a key role in drawing up the 1943 BRUSA Agreement . National Security Agency . Following World War II , Friedman remained in government signals intelligence . In 1949 he became head of the cryptographic division of the newly formed Armed Forces Security Agency ( AFSA ) and in 1952 became chief cryptologist for the National Security Agency ( NSA ) when it was formed to take over from AFSA . Friedman produced a classic series of textbooks , " Military Cryptanalysis " , which was used to train NSA students . ( These were revised and extended , under the title " Military Cryptanalytics " , by Friedman ' s assistant and successor Lambros D . Callimahos , and used to train many additional cryptanalysts . ) During his early years at NSA , he encouraged it to develop what was probably the first super - computers , although he was never convinced a machine could have the " insight " of a human mind . Friedman spent much of his free time trying to decipher the famous Voynich Manuscript , written sometime between 1403 – 1437 . However , after four decades of study he finally had to admit defeat , contributing no more than an educated guess as to its origins and meaning . Friedman retired in 1956 and , with his wife , turned his attention to the problem that had originally brought them together : examining Bacon ' s supposed codes . Together they wrote a book entitled " The Cryptologist Looks at Shakespeare " which won a prize from the Folger Library and was published under the title " The Shakespearean Ciphers Examined . " The book demonstrated flaws in Gallup ' s work and in that of others who sought hidden ciphers in Shakespeare ' s work . At NSA ' s request Friedman prepared " Six Lectures Concerning Cryptography and Cryptanalysis " , which he delivered at NSA . But later the Agency , concerned about security , confiscated the reference materials from Friedman ' s home . Death and legacy . Friedman ' s health began to fail in the late 1960s , and he died in 1969 . Friedman and his wife donated their archives to the library of the George C . Marshall Foundation , which also has had material reclassified and removed by the NSA . Friedman has been inducted into the Military Intelligence Hall of Fame and there is a building named after William and Elizebeth at the NSA complex at Fort George G . Meade in Maryland . He was also presented the Medal for Merit by President Harry Truman , and the National Security Medal by Dwight Eisenhower . Friedman has the distinction of having one of the longest known suppressed patent applications , for , a patent for a " cryptographic system " . It was filed on July 25 , 1933 , issued on August 1 , 2000 . References . Notes Bibliography