PROPHET OF PRIVACY
                                       
   He took cryptography out of the hands of the spooks and made privacy
   possible in the digital age, by inventing the most revolutionary
   concept in encryption since the Renaissance.
   
   Steven Levy decodes Whitfield Diffie
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   The heat on this steamy June day is oppressive, but Whitfield Diffie
   doesn't seem to notice. He strides across the street from his hotel to
   the Washington, DC, Convention Center like a smart bomb homing in on a
   bunker. He has prepared for the Armed Forces Communications and
   Electronics Association Expo and Convention with his usual compulsive
   vigor. Some days before, in his office at Sun Microsystems Computer
   Corporation in Mountain View, California - where he holds the title of
   distinguished engineer - Diffie examined the list of exhibitors and
   methodically charted a course through the convention center that would
   take him past every vendor or organization that offers something
   related to the field he has helped revolutionize: cryptography.
   
   Diffie is quite at home in Washington. In the past 15 months he has
   testified three times before Congress and participated in a
   blue-ribbon panel on the future of crypto. This swing started two days
   ago, on his 50th birthday. He celebrated by having a quiet dinner with
   his wife, Egyptologist Mary Fischer. The following day he denounced
   the Clipper Chip at a conference organized by the Electronic Privacy
   Information Center. Now - accompanied by a small entourage of authors,
   including David Kahn (The Codebreakers), Bruce Schneier (Applied
   Cryptography), and me - he is ready to hit the convention floor of the
   Armed Forces show, where the theme of the day is "Digitizing the
   Battlefield."
   
   Even if he weren't leading a crew of cypherscribes, Diffie would cut
   an imposing figure. From the neck down, he fits the conservative mode
   of the bureaucrats, techies, and spooks in attendance: blue suit with
   a neatly knotted tie over a blue shirt. But hovering over the suit are
   piercing blue eyes framed by shoulder-length blonde hair and a beard
   worthy of Buffalo Bill. Then there's his unforgettable voice: Diffie
   speaks in a cutting tremolo that heightens the effect of his words,
   which are often already provocative.
   
   Diffie has a chance to exercise these vocal proclivities as he jaunts
   from booth to booth, happily bantering with the purveyors of
   surveillance systems, crypto-protected jeep communications, and
   "situation awareness" helmets with built-in quanta-ray sensors. At one
   modest display he jokes, "For an outfit of your formidability, you've
   managed an economical booth." The exhibitors wilt. At another booth he
   is offered a chance to try out an encryption-equipped walkie-talkie.
   "Presumably, we'll discover it works just fine," says Diffie, refusing
   the demo.
   
   Then Diffie reaches Booth 660, let by the National Security Agency.
   The agency is the world's largest repository of information about
   cryptography and usually operates under total secrecy. In these aprŠs
   Cold War days, however, the agency has been experimenting with a more
   public posture, and at the conference it has fronted two booths: this
   one, with its banner proudly unfurled, and an exhibit room off the
   show floor.
   
   A helpful NSA employee shows Diffie and company to the latter. It's
   hardly different from any other vendor's operation at a high-tech
   convention - except that visitors must provide social security numbers
   and proof of US citizenship. The room is filled with several elaborate
   demos of cryptosystems running off PC nets. Diffie examines a system
   that allows several levels of encryption to coexist on a network. The
   young agency technician running the demo is obviously bright, perhaps
   even a bit haughty as he runs the system through its paces. As Diffie
   turns away, someone asks the technician if he recognized that bearded
   fellow.
   
   "Who?" the technician asks.
   
   "That's Whitfield Diffie. He invented public key cryptography."
   
   The technician's eyes widen to the size of video monitors. For a
   second he is paralyzed. Then he bolts forward. "Dr. Dif-fffffie...,"
   he shouts, "Dr. Dif-fffeeeeee..." When he catches up, his attempt to
   describe his awe comes out in a jumble. For a moment it looks like he
   might outstretch his arms and execute knee-bend bows, … la Wayne and
   Garth: "I'm not worthy!"
   
   It was in 1976 that Diffie and Stanford University electrical
   engineering professor Martin Hellman blew open the cryptographic world
   by announcing a new way to protect secrets: the public key. It was a
   profound discovery; historian David Kahn (still in tow as Diffie
   leaves the booth) called it "the most revolutionary new concept in the
   field since the Renaissance." A pursuit formerly limited to the domain
   of spies, diplomats, and the military now had the potential to enhance
   the privacy of the masses. Public key has the potential to change the
   way we work, even the way we live.
   
   Compared to ordinary encryption, public key is a type of magic. By
   splitting the scrambling-and-descrambling "key" into two components, a
   widely distributed public key and a closely held private key, it
   enables users to communicate in complete secrecy with people they've
   never met. And when that person replies, only the user will be able to
   read that message. Even more remarkable, it makes possible a "digital
   signature," assuring that an electronic message was generated by the
   person who claims responsibility for it. Together, these features
   allow us to create new forms of digital commerce with an unprecedented
   level of privacy. These possibilities also present a challenge to
   government, particularly to the NSA, which is accustomed to
   controlling the nation's cryptosystems. As cryptography slips into the
   mainstream, the agency is faced with a dramatic reassessment of its
   mission.
   
   And looking over the agency's shoulder is Whit Diffie, who has emerged
   as a passionate and public critic of government cryptographic policy.
   His eloquence alone would make him a formidable figure in the debate
   over whether the feds should limit the spread of crypto, but his
   credentials make him a figure truly to be reckoned with. "I would say
   he is the elder statesman of cryptography," says Jim Bidzos, president
   of RSA Data Security. "Few people have the kind of insights he does."
   
   Yet at one time, it looked like Diffie might slip into obscurity as an
   eccentric hacker who never made much of his genius for math and his
   laser-focus mind. As his wife tells it, on the very eve of the
   historic discovery of public key crypto, Diffie was virtually
   despondent. "He was telling me that he should do something else,"
   recalls Mary Fischer, "that he was a broken-down researcher."
   
   This was 1975. Diffie was 31, with only a bachelor's degree, and he
   had reached a point in life where, he says, "I was worried that I
   wasn't particularly remarkable as a programmer and that my lot in life
   would get progressively worse if things continued going as they were."
   All his life Diffie had jigged in perfect cadence to an internal tune,
   heeding little of convention. Had the music led him to a dead end?
   
   
   
   Whit Diffie, it seems, had always been different. Born in 1944, he was
   the sole offspring of Bailey Wallace Diffie and Justine Louise
   Whitfield. They had met as foreign service workers in Madrid in the
   1920s and married in Paris in 1928. Diffie senior became a City
   College of New York history professor specializing in Iberia and its
   colonies, and Whit grew up in Queens, in perhaps the only atheist
   Camelite household in a mostly Jewish neighborhood. "One of Whit's
   oldest friends told me he had an alternative lifestyle at age 5," says
   Mary Fischer.
   
   Diffie didn't learn to read until he was 10 years old. There was no
   question of disability; it was obvious he was a bright, curious child.
   He simply didn't read, and no one considered it a horrible problem.
   During the fifth grade he spontaneously worked his way through a tome
   called The Space Cat and immediately progressed to one of the Wizard
   of Oz books. Later that year, his teacher at PS 78 - "Her name was
   Mary E. Collins and if she is still alive I would like to find her,"
   says Diffie - spent an afternoon on the subject of ciphers, and Diffie
   was so taken he had his father check out all the cryptography books in
   the City College library. But his code mania soon faded, and he
   pursued other interests - castles, camouflage rockets, and poison
   gases. (As late as his junior year in high school, he considered a
   career in the military.) Diffie also became interested in math - "I
   thought of myself as a mathematician in high school," he says.
   
   At the Massachusetts Institute of Technology, he harbored contempt for
   computers - he thought himself too pure a mathematician to have much
   truck with them. This began to change after he earned his degree in
   1965. The Vietnam War dampened Diffie's military enthusiasm, and he
   became a self-described "peacenik," with no desire to deploy the armed
   rockets and poison gases that had entranced him in his youth. Like
   many, he found a way to avoid the draft - working for a defense
   contractor. It was the Mitre Corporation, a Massachusetts systems
   engineering company that worked for the Defense Department. The job
   was a plum - while technically a Mitre employee, he would write LISP
   code at the MIT Artificial Intelligence Lab. There Diffie was exposed
   to the best computer hackers in the world. By the time he left Mitre
   in 1969, Diffie was over his contempt for computers.
   
   Ever since his freshman year at MIT, though, when he spent the summer
   in Berkeley, Diffie had been pining to move west. "I hung out with the
   red diaper set in New York, the frontier of the sexual revolution. I'd
   been used to having a full social life - folk singing parties and
   stuff like that. There were such scenes in Cambridge, but I fell in
   with what was easy: hanging out with these guys at MIT's East Campus -
   with 25 women in a class of 950, it was a Boy Scout camp. But when I
   went back to Berkeley, immediately I was in among what I thought of as
   the real people. I have always believed the thesis that one's politics
   and the character of one's intellectual work are inseparable."
   
   Diffie got his chance to go west when he heard that artificial
   intelligence pioneer John McCarthy was interested in a mathematical
   problem that fascinated Diffie: proof of correctness of programs.
   Diffie was hired to work at Stanford's Artificial Intelligence Lab,
   where McCarthy was a professor. But he now conjectures, "In his view,
   McCarthy probably hired me as the LISP system programmer."
   Nonetheless, Diffie's work in proof of correctness (funded,
   ironically, by the NSA) apparently met with McCarthy's approval. Then
   McCarthy, in essence, lost Diffie as a worker by urging him to
   consider crypto once more. Diffie's long-dormant penchant for
   cryptography was quickly rekindled, and he began working on crypto
   obsessively.
   
   There areious. I
   felt that if I could just get to the bottom of this it would somehow
   be incredibly satisfying."
   
   Diffie poured over David Kahn's 1,164-page 1967 opus, The
   Codebreakers. "It must have taken me a year to read it," he says. "I
   read it more carefully probably than anyone had ever read it. It's
   like the Veda - in India if a man loses his cow, he looks for it in
   the Veda. In any event, by the spring of 1973, I was doing nothing but
   cryptography."
   
   Diffie took a leave from the AI lab and embarked on an epic sojourn to
   discover cryptographic truths. It was a lonely quest. True, NSA
   headquarters at Fort Meade, Maryland, was teeming with people working
   on these problems, but all the results were classified. Precious
   little information about the subject existed in the public domain. If
   someone did publish something, or try to patent a cryptographic
   innovation, the agency might attempt to classify that information. "My
   attitude was to keep my head down at first," says Diffie.
   
   For two years, Diffie crisscrossed the country in a Datsun 510. He hit
   every library that might have some information and attempted to talk
   to anyone whose ideas might inform his own. Some people refused to
   talk to him. But the journey helped in establishing the key problems
   Diffie needed to tackle in cryptography. (Besides, the trip wasn't all
   cryptography: he managed to take in several Skylab launches and, most
   significantly, to hook up with Fischer, who became his traveling
   companion.)
   
   When Diffie and Fischer finally returned to the West Coast in the fall
   of 1974, Diffie heard about a Stanford prof named Martin Hellman who
   was also interested in crypto. Diffie gave him a call; Hellmon that it came from a
   certain person, in the same way a written signature indelibly
   identifies a document?
   
   Pondering some ideas that came from techniques in military
   "identification friend or foe" systems, and combining them with an
   innovative scheme of protecting computer passwords using a
   mathematical technique called one-way functions, Diffie came up with a
   method to solve the authentication problem - a true digital signature.
   Two weeks later, he realized that by cracking that puzzle, he had also
   uncovered a way to solve the encryption problem - an amazing solution
   that used not one but two cryptographic keys.
   
   He clearly remembers that day in May 1975. He and Fischer were living
   in John McCarthy's house, with the understanding that Diffie would act
   as a househusband, taking care of McCarthy's daughter and watching the
   house, while McCarthy was on leave. His routine at the time was to fix
   Mary breakfast before she went to work at her job analyzing geologic
   findings at British Petroleum. Then he would spend the rest of the day
   alternating between domestic chores and research. Sometime during that
   afternoon he altered the course of cryptographic history by "splitting
   the key."
   
   "The thing I remember distinctly is that I was sitting in the living
   room when I thought of it the first time and then I went downstairs to
   get a Coke and I almost lost it," he says. "I mean, there was this
   moment when - I was thinking about something. What was it? And then I
   got it back and didn't forget it."
   
   That night, he went over to Hellman's and told his collaborator about
   the idea. Hellman recalls during the brief conversation that he first
   thought Diffie's heretical idea "was a little bit crazy." But as he
   thought about it later that night, he beganing jobs with either of
   the two most common employers of cryptographers - the government and
   academia. In 1978 he took a job as manager of secure systems research
   for Northern Telecom, the Canadian equivalent of Western Electric,
   working in its laboratory in Mountain View, California. One of the
   best pieces of work he did there was designing a secure phone system;
   it never saw commercial use, but part of its design became the heart
   of an innovative product called PDSO, or packet data security overlay,
   used to provide end-to-end security between hosts on packet data
   networks. In 1991, Diffie moved to Sun Microsystems, where he became a
   sort of internal consultant, a companywide resource on security
   issues. And, of course, a crypto researcher.
   
   "You know, I never know exactly what I do," Diffie says of the latter
   work. "I mean, every now and then, of course, I produce something, so
   I can say, 'I did that,' but most of the time Ictually need them. Prior to Aldrich Ames, two of the
   most damaging spy scandals of the last 20 years in the US - Boyce and
   Lee at TRW and the Walker ring in the Navy -- resulted from the fact
   that keys existed for longer than they needed to exist, and somebody
   got a chance to siphon some of them off. If you use public key
   correctly, particularly in interactive channels like telephones, you
   can avoid having this hazard. The keys exist only in the equipment,
   only for the duration of the call, and after that they go away. And so
   key escrow is just rescuing a dreadful vulnerability." (For more on
   public key encryption, see "Cypher Wars," page 129).
   
   The Clipper Chip is even less attractive, says Diffie, when one
   considers who's pushing it. "We're moving our society into a
   telecommunications environment. I think security mechanisms are
   fundamental social mechanisms, and what is needed is widespread trust
   in them - but there's no trusting secret mechanisms designed by an
   organization most of whose budget goes to spying."
   
   One would think that this sort of talk would place Diffie's picture at
   the top of an NSA enemy list. But relations between the agency and its
   most eloquent opponent are cordial. Clinton Brooks, an important
   architect of the NSA's key escrow scheme, has worked with Diffie on
   the Association of Computing Machinery's panel on crypto policy. "We
   came to this from quite different perspectives," says Brooks, with
   some understatement. "During this experience, my esteem and regard for
   Whit considerably increased. I found him open, considerate, and eager
   to listen to others' points of view."
   
   The respect is mutual. Even Diffie has tempered his opinion of the
   organization. "I started out being very antagonistic to them, but
   after a decade of studying their technology and history, I came to
   like and respect them much more. I believe I recognize and have for a
   long time been sympathetic to NSA's goals. I think from a purely
   nationalistic point of view those goals are certainly understandable.
   That does not mean that there are not other objectives that seem even
   more important. Personal privacy certnd beyond and laid out the Clipper controversy in
   dazzling context. Crypto, he argued, will not upset the balance of
   power by giving the individual a huge edge over the government -
   instead we should see it as one of the few resources available to the
   individual who wants some privacy. "It has been thoughtlessly said ...
   that cryptography brings the unprecedented promise of absolute
   privacy," testified Diffie. "In fact, it only goes a short way to make
   up for the loss of an assurance of privacy that can never be
   regained."
   
   In the flurry of concepts, however, few appreciated the resonance of
   Diffie's opening sentences. They summed up Whitfield Diffie's progress
   since he began his quest more than two decades ago.
   
   "I first began thinking about cryptography in 1972," he testified. "My
   feeling was that cryptography was vitally important for personal
   privacy, and my goal was to make it better known. I am pleased to say
   that if I have succeeded in nothing else, I have achieved that goal."
   
   In spades.
   
   
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   Steven Levy (steven@echonyc.com) is a Fellow at the Freedom Forum
   Media Studies Center. He is author of Hackers, Insanely Great, and
   other books.
   
   
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