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A PIONEER IN CRYPTOLOGY 
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In a 1924 photograph, Friedman sits ar a cipher machine that created random alphabets. Comparable machines were used widely rn World War II. 

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\ THE GENIUS WHO BUILT 

THE PURPLE MACHINE 

To the men and women who worked with him, William 

Friedman's building of the Purple cipher machine to break 

the Japanese diplomatic code (pages 56-57) was no surprise. Since World War I he had been devising and unraveling codes with dazzling insight and a speciaJ imaginative 

flair, as the class picture on the preceding page suggests. 

While teaching classes of Army officers in 1917-1918, 

Friedman wrote a series of instruction manuals laying down 

mathematical principles that transformed cryptology from 

an intuitive craft into a full-fledged science. As the preeminent practitioner of that science, he trained a whole 

generation of cryptologists in the rigorously analytic techniques that enabled the United States to become the leading 

nation in the field by the eve of World War II. 

Friedman started his career at a time when global rivalries 

and the advent of radiotelegraphy were increasing the traffic 

in encoded messages. The 1920s saw the introduction of 

a variety of electromechanical enciphering systems, most 

of them involving multiple-rotor machines that produced 

codes far more complex than any dreamed of before. As 

chief codebreaker for the Army Signal Corps, Friedman 

used mathematical inductive reasoning to reconstruct the 

new machines and crack their codes, thus laying the foundation for solving all modern rotor-machine puzzles. 

By the mid: 1930s Friedman had beco·me Chief Cryptanalyst of the War Department, charged with directing U.S. 

Army.cod~breaking efforts: His chief responsibility quickly 

became the breaking of the codes that the Japanese introduced in 1934, after the American press had revealed that 

the United State~,government was eavesdropping on diplomatic traffic from Tokyo. 

When the War came, Friedman's staff outgrew its little office in the War Department and moved into the campus 

buildings at Arlington Hall, a former girls' school in Virginia. The work that went on there was unknown to the public. 

but Army Chief of Staff General George C. Marshall called it· 

the determining factor in "the conduct of General Eisenhower's campaign and of all operations in the Pacific." 

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A~ c1v1/1an head of the Signal Security Agency of the U.S. Army, a fell-hatted Friedman arrives to lake possession of Ar/inglon Hall for the agency in 1942. 

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As a Cornell student, Friedman conducts plant-genetics studies in an insect-free hut at a Carnegie Institution exper1mental station in 1913. 

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Elizebeth Smith stands beside emplot•er George Fabyan in 1~16. 

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FROM PLAIT GENETICS 

TO SECRET CIPHERS 

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Friedman found his calling indirectly. He 

~t out to be a botanist. But in 1915, as a 

fledgling scientist, he worked on the Illinois iarm of an eccentric millionaire, 5=olonel George Fabyan. There ne;net Elizt;f 

beth Smith,~ho was hired-·i:o' pore over 

Shakespeare's plays in search of a cipher 

that the colonel fancied would prove Francis Bacon the real playwright. That was labor lost. But Friedman fell in love with 

both Miss Smith and cryptology, marrying 

one and making the other his career. 

In 1918 the American Telephone and 

Telegraph Company introduced a cipher 

machrhe that worked on the principle of 

the brnary cipher-using as the two elements the presence or absence of perforations on a tape.· Friedman cracked its system in six weeks, making himself famous. 

Sil< years later, when the U.S. Army mistook some radio signals for messages from 

Mars. Friedman was naturally the man the 

Army consulted to try to figure them out. 

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Friedman SllS at the keyboard of an American Telephone and Telegraph cfphermachine in °1919: • 

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FrrE'dman /center} and two co//eaguf:S tr)' to decipher radio signals thought to have originated on the planet Mars, which came close to E.arth in 1924. 

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Part l4 of l4 

(lot.e: ID t.i.. to~ f.nst.ruct.icxw t.o the 

radio at.at.ion h&ndl:l.ng t.hs. part.• &ppe&Z'9d t.be 

plain !ngliah phr'ue "TllR!' DIPalT.AJrT•} 

7. ObriouaJ.T it. 1a the int.em.ion of the .a..ricmi 

GoveZ'lllllent. t.o conapir'e with Qr-eat. BM.t.&in and ot.ti.r count.nee 

t.o obet.ruct. Japan•• effort.a toward th• ••t.&b~t. ~ 

peace t.hrough t.he creat.1on of a ._ Ord9r 1n But. .bi.a, 

and e•pec1all.7 t.o J>Z'U•l"'AI .Anglo-U.ricmi righta and int.erMt.a 

b7 k .. ping Japan and Chin& at. war. 'fhia intent.ioa hu 

~ l"ft'aa.l9d cl.arl.T during the COUl'll• ot the preawit. 

negot.1&t.1ona. Thua • the eamut. hope of t.he J&p&IW•• 

Clc>Yemaent. to adjust. Japanea-American relat.ion11 and to pruerve and promot.a the peace of tM Pac1t'1c through 

cooperat.1on wit.h the American Go"'"9mlt. haa rin&ll,r 'bMll 

lost.. 

'!h• Japan••• :lar•~t. regret.a to have t.o not.117 

herebJ' ti. .American eov..m-it. that 1n rt- ot t.h• att.itud9 

ot th• American Ooven..it it cannot. but consider that it 1a 

iapoaaible to reach M acr-t t.hrou&Jt turther negatiat.loaa. 

(II} Na'WJ' tram. 7 Dec. 1941 (S-TT) 

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. - .:- A MAS~lllE ASSAULT - - _ -~ -.-~..,...,_......_ 

-011 A CIPHER MACHlllE, -_- · _ · -~ 

: --~'\~the. ~~3os;~~~~fr~~ ~n~ii~!~;;ad .:~=~~ .. - - ,,,.. some s~~ .~,,~~1ectr.omechanical encipher- .. _ -

~- _ - •· · _ ing device . .-Among t~.~--'!l<?~t sophisticated-· • ..,~ 

_ . of these ·was· the one that from 1937 on • -

• ~:. -. -transmitted~th~.Japar:i~~e~ dlplo~~tic c~de, . 

, -• . nicknamed l,urple by American cryptana- ' : : .:! · -~ ._,. :, lysts. ~f'i9rtly_.aftet11J.ej;-urple code was~ i ·~ -~~ -- p~t in~ -~s_e; bre~~~g ;!H~~~a_l!.'e 'XJJliam,. -i ~ 

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__ : .• SupportinEr him w~~-~-superb team ~hat .~ ~ .. 

he had start.ed recruiting· in 1930 from • -~ 

scholars in such disciplines as mathemat- · 

ics and linguistics~ For 18 ne.rve-racking 

months, Friedman's team tried to duplicate the Japanese machine. 

Instead of being based on rotors, the 

machine worked on the principle.of a telephone switchboard, using plugs to shuffle 

arrangements of letters. When a replica 

Purple machine was finally hand-built in 

August of 1940, the United States had an 

instrument that enabled it to eavesdrop 

on such diplomatic fare as Germany's efforts to press lapan into war against Great 

Britain in March 1941. 

The effort to build the machine told on 

everyone. It was, one cryptanalyst said, 

like being "engulfed in an interminable 

polar night." Friedman himself suffered a 

nervous collapse. ~. 

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Built from readily ;{va11;i,/e Wifes and screws, this American machine broke Japan's Piirple code. 

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